diff --git a/configure b/configure
index 25120337de..4908831477 100755
--- a/configure
+++ b/configure
@@ -2271,6 +2271,7 @@ CONFIG_EXTRA="
     bswapdsp
     cabac
     cbs
+    cbs_av1
     cbs_h264
     cbs_h265
     cbs_mpeg2
@@ -2534,6 +2535,7 @@ w32threads_deps="atomics_native"
 threads_if_any="$THREADS_LIST"
 
 # subsystems
+cbs_av1_select="cbs"
 cbs_h264_select="cbs golomb"
 cbs_h265_select="cbs golomb"
 cbs_mpeg2_select="cbs"
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index ba2158f997..e8d5f74067 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -63,6 +63,7 @@ OBJS-$(CONFIG_BLOCKDSP)                += blockdsp.o
 OBJS-$(CONFIG_BSWAPDSP)                += bswapdsp.o
 OBJS-$(CONFIG_CABAC)                   += cabac.o
 OBJS-$(CONFIG_CBS)                     += cbs.o
+OBJS-$(CONFIG_CBS_AV1)                 += cbs_av1.o
 OBJS-$(CONFIG_CBS_H264)                += cbs_h2645.o h2645_parse.o
 OBJS-$(CONFIG_CBS_H265)                += cbs_h2645.o h2645_parse.o
 OBJS-$(CONFIG_CBS_MPEG2)               += cbs_mpeg2.o
diff --git a/libavcodec/av1.h b/libavcodec/av1.h
index c989b69974..f2ec39c86b 100644
--- a/libavcodec/av1.h
+++ b/libavcodec/av1.h
@@ -39,4 +39,92 @@ typedef enum {
     AV1_OBU_PADDING                = 15,
 } AV1_OBU_Type;
 
+// Metadata types (section 6.7.1).
+enum {
+    AV1_METADATA_TYPE_HDR_CLL     = 1,
+    AV1_METADATA_TYPE_HDR_MDCV    = 2,
+    AV1_METADATA_TYPE_SCALABILITY = 3,
+    AV1_METADATA_TYPE_ITUT_T35    = 4,
+    AV1_METADATA_TYPE_TIMECODE    = 5,
+};
+
+// Frame types (section 6.8.2).
+enum {
+    AV1_FRAME_KEY        = 0,
+    AV1_FRAME_INTER      = 1,
+    AV1_FRAME_INTRA_ONLY = 2,
+    AV1_FRAME_SWITCH     = 3,
+};
+
+// Reference frames (section 6.10.24).
+enum {
+    AV1_REF_FRAME_INTRA   = 0,
+    AV1_REF_FRAME_LAST    = 1,
+    AV1_REF_FRAME_LAST2   = 2,
+    AV1_REF_FRAME_LAST3   = 3,
+    AV1_REF_FRAME_GOLDEN  = 4,
+    AV1_REF_FRAME_BWDREF  = 5,
+    AV1_REF_FRAME_ALTREF2 = 6,
+    AV1_REF_FRAME_ALTREF  = 7,
+};
+
+// Constants (section 3).
+enum {
+    AV1_MAX_OPERATING_POINTS = 32,
+
+    AV1_MAX_SB_SIZE    = 128,
+    AV1_MI_SIZE        = 4,
+
+    AV1_MAX_TILE_WIDTH = 4096,
+    AV1_MAX_TILE_AREA  = 4096 * 2304,
+    AV1_MAX_TILE_ROWS  = 64,
+    AV1_MAX_TILE_COLS  = 64,
+
+    AV1_NUM_REF_FRAMES       = 8,
+    AV1_REFS_PER_FRAME       = 7,
+    AV1_TOTAL_REFS_PER_FRAME = 8,
+    AV1_PRIMARY_REF_NONE     = 7,
+
+    AV1_MAX_SEGMENTS = 8,
+    AV1_SEG_LVL_MAX  = 8,
+
+    AV1_SEG_LVL_ALT_Q      = 0,
+    AV1_SEG_LVL_ALT_LF_Y_V = 1,
+    AV1_SEG_LVL_REF_FRAME  = 5,
+    AV1_SEG_LVL_SKIP       = 6,
+    AV1_SEG_LVL_GLOBAL_MV  = 7,
+
+    AV1_SELECT_SCREEN_CONTENT_TOOLS = 2,
+    AV1_SELECT_INTEGER_MV           = 2,
+
+    AV1_SUPERRES_NUM       = 8,
+    AV1_SUPERRES_DENOM_MIN = 9,
+
+    AV1_INTERPOLATION_FILTER_SWITCHABLE = 4,
+
+    AV1_GM_ABS_ALPHA_BITS       = 12,
+    AV1_GM_ALPHA_PREC_BITS      = 15,
+    AV1_GM_ABS_TRANS_ONLY_BITS  = 9,
+    AV1_GM_TRANS_ONLY_PREC_BITS = 3,
+    AV1_GM_ABS_TRANS_BITS       = 12,
+    AV1_GM_TRANS_PREC_BITS      = 6,
+    AV1_WARPEDMODEL_PREC_BITS   = 16,
+
+    AV1_WARP_MODEL_IDENTITY    = 0,
+    AV1_WARP_MODEL_TRANSLATION = 1,
+    AV1_WARP_MODEL_ROTZOOM     = 2,
+    AV1_WARP_MODEL_AFFINE      = 3,
+};
+
+
+// The main colour configuration information uses the same ISO/IEC 23001-8
+// (H.273) enums as FFmpeg does, so separate definitions are not required.
+
+// Chroma sample position.
+enum {
+    AV1_CSP_UNKNOWN   = 0,
+    AV1_CSP_VERTICAL  = 1, // -> AVCHROMA_LOC_LEFT.
+    AV1_CSP_COLOCATED = 2, // -> AVCHROMA_LOC_TOPLEFT.
+};
+
 #endif /* AVCODEC_AV1_H */
diff --git a/libavcodec/cbs.c b/libavcodec/cbs.c
index be6c043b58..f0b1b7de7c 100644
--- a/libavcodec/cbs.c
+++ b/libavcodec/cbs.c
@@ -29,6 +29,9 @@
 
 
 static const CodedBitstreamType *cbs_type_table[] = {
+#if CONFIG_CBS_AV1
+    &ff_cbs_type_av1,
+#endif
 #if CONFIG_CBS_H264
     &ff_cbs_type_h264,
 #endif
@@ -44,6 +47,9 @@ static const CodedBitstreamType *cbs_type_table[] = {
 };
 
 const enum AVCodecID ff_cbs_all_codec_ids[] = {
+#if CONFIG_CBS_AV1
+    AV_CODEC_ID_AV1,
+#endif
 #if CONFIG_CBS_H264
     AV_CODEC_ID_H264,
 #endif
diff --git a/libavcodec/cbs_av1.c b/libavcodec/cbs_av1.c
new file mode 100644
index 0000000000..9bac9dde09
--- /dev/null
+++ b/libavcodec/cbs_av1.c
@@ -0,0 +1,1320 @@
+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "libavutil/avassert.h"
+#include "libavutil/pixfmt.h"
+
+#include "cbs.h"
+#include "cbs_internal.h"
+#include "cbs_av1.h"
+#include "internal.h"
+
+
+static int cbs_av1_read_uvlc(CodedBitstreamContext *ctx, GetBitContext *gbc,
+                             const char *name, uint32_t *write_to,
+                             uint32_t range_min, uint32_t range_max)
+{
+    uint32_t value;
+    int position, zeroes, i, j;
+    char bits[65];
+
+    if (ctx->trace_enable)
+        position = get_bits_count(gbc);
+
+    zeroes = i = 0;
+    while (1) {
+        if (get_bits_left(gbc) < zeroes + 1) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid uvlc code at "
+                   "%s: bitstream ended.\n", name);
+            return AVERROR_INVALIDDATA;
+        }
+
+        if (get_bits1(gbc)) {
+            bits[i++] = '1';
+            break;
+        } else {
+            bits[i++] = '0';
+            ++zeroes;
+        }
+    }
+
+    if (zeroes >= 32) {
+        value = MAX_UINT_BITS(32);
+    } else {
+        value = get_bits_long(gbc, zeroes);
+
+        for (j = 0; j < zeroes; j++)
+            bits[i++] = (value >> (zeroes - j - 1) & 1) ? '1' : '0';
+
+        value += (1 << zeroes) - 1;
+    }
+
+    if (ctx->trace_enable) {
+        bits[i] = 0;
+        ff_cbs_trace_syntax_element(ctx, position, name, NULL,
+                                    bits, value);
+    }
+
+    if (value < range_min || value > range_max) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "%s out of range: "
+               "%"PRIu32", but must be in [%"PRIu32",%"PRIu32"].\n",
+               name, value, range_min, range_max);
+        return AVERROR_INVALIDDATA;
+    }
+
+    *write_to = value;
+    return 0;
+}
+
+static int cbs_av1_write_uvlc(CodedBitstreamContext *ctx, PutBitContext *pbc,
+                              const char *name, uint32_t value,
+                              uint32_t range_min, uint32_t range_max)
+{
+    uint32_t v;
+    int position, zeroes;
+
+    if (value < range_min || value > range_max) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "%s out of range: "
+               "%"PRIu32", but must be in [%"PRIu32",%"PRIu32"].\n",
+               name, value, range_min, range_max);
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (ctx->trace_enable)
+        position = put_bits_count(pbc);
+
+    if (value == 0) {
+        zeroes = 0;
+        put_bits(pbc, 1, 1);
+    } else {
+        zeroes = av_log2(value + 1);
+        v = value - (1 << zeroes) + 1;
+        put_bits(pbc, zeroes + 1, 1);
+        put_bits(pbc, zeroes, v);
+    }
+
+    if (ctx->trace_enable) {
+        char bits[65];
+        int i, j;
+        i = 0;
+        for (j = 0; j < zeroes; j++)
+            bits[i++] = '0';
+        bits[i++] = '1';
+        for (j = 0; j < zeroes; j++)
+            bits[i++] = (v >> (zeroes - j - 1) & 1) ? '1' : '0';
+        bits[i++] = 0;
+        ff_cbs_trace_syntax_element(ctx, position, name, NULL,
+                                    bits, value);
+    }
+
+    return 0;
+}
+
+static int cbs_av1_read_leb128(CodedBitstreamContext *ctx, GetBitContext *gbc,
+                               const char *name, uint64_t *write_to)
+{
+    uint64_t value;
+    int position, err, i;
+
+    if (ctx->trace_enable)
+        position = get_bits_count(gbc);
+
+    value = 0;
+    for (i = 0; i < 8; i++) {
+        int subscript[2] = { 1, i };
+        uint32_t byte;
+        err = ff_cbs_read_unsigned(ctx, gbc, 8, "leb128_byte[i]", subscript,
+                                   &byte, 0x00, 0xff);
+        if (err < 0)
+            return err;
+
+        value |= (uint64_t)(byte & 0x7f) << (i * 7);
+        if (!(byte & 0x80))
+            break;
+    }
+
+    if (ctx->trace_enable)
+        ff_cbs_trace_syntax_element(ctx, position, name, NULL, "", value);
+
+    *write_to = value;
+    return 0;
+}
+
+static int cbs_av1_write_leb128(CodedBitstreamContext *ctx, PutBitContext *pbc,
+                                const char *name, uint64_t value)
+{
+    int position, err, len, i;
+    uint8_t byte;
+
+    len = (av_log2(value) + 7) / 7;
+
+    if (ctx->trace_enable)
+        position = put_bits_count(pbc);
+
+    for (i = 0; i < len; i++) {
+        int subscript[2] = { 1, i };
+
+        byte = value >> (7 * i) & 0x7f;
+        if (i < len - 1)
+            byte |= 0x80;
+
+        err = ff_cbs_write_unsigned(ctx, pbc, 8, "leb128_byte[i]", subscript,
+                                    byte, 0x00, 0xff);
+        if (err < 0)
+            return err;
+    }
+
+    if (ctx->trace_enable)
+        ff_cbs_trace_syntax_element(ctx, position, name, NULL, "", value);
+
+    return 0;
+}
+
+static int cbs_av1_read_su(CodedBitstreamContext *ctx, GetBitContext *gbc,
+                           int width, const char *name,
+                           const int *subscripts, int32_t *write_to)
+{
+    uint32_t magnitude;
+    int position, sign;
+    int32_t value;
+
+    if (ctx->trace_enable)
+        position = get_bits_count(gbc);
+
+    if (get_bits_left(gbc) < width + 1) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid signed value at "
+               "%s: bitstream ended.\n", name);
+        return AVERROR_INVALIDDATA;
+    }
+
+    magnitude = get_bits(gbc, width);
+    sign      = get_bits1(gbc);
+    value     = sign ? -(int32_t)magnitude : magnitude;
+
+    if (ctx->trace_enable) {
+        char bits[33];
+        int i;
+        for (i = 0; i < width; i++)
+            bits[i] = magnitude >> (width - i - 1) & 1 ? '1' : '0';
+        bits[i] = sign ? '1' : '0';
+        bits[i + 1] = 0;
+
+        ff_cbs_trace_syntax_element(ctx, position,
+                                    name, subscripts, bits, value);
+    }
+
+    *write_to = value;
+    return 0;
+}
+
+static int cbs_av1_write_su(CodedBitstreamContext *ctx, PutBitContext *pbc,
+                            int width, const char *name,
+                            const int *subscripts, int32_t value)
+{
+    uint32_t magnitude;
+    int sign;
+
+    if (put_bits_left(pbc) < width + 1)
+        return AVERROR(ENOSPC);
+
+    sign      = value < 0;
+    magnitude = sign ? -value : value;
+
+    if (ctx->trace_enable) {
+        char bits[33];
+        int i;
+        for (i = 0; i < width; i++)
+            bits[i] = magnitude >> (width - i - 1) & 1 ? '1' : '0';
+        bits[i] = sign ? '1' : '0';
+        bits[i + 1] = 0;
+
+        ff_cbs_trace_syntax_element(ctx, put_bits_count(pbc),
+                                    name, subscripts, bits, value);
+    }
+
+    put_bits(pbc, width, magnitude);
+    put_bits(pbc, 1, sign);
+
+    return 0;
+}
+
+static int cbs_av1_read_ns(CodedBitstreamContext *ctx, GetBitContext *gbc,
+                           uint32_t n, const char *name,
+                           const int *subscripts, uint32_t *write_to)
+{
+    uint32_t w, m, v, extra_bit, value;
+    int position;
+
+    av_assert0(n > 0);
+
+    if (ctx->trace_enable)
+        position = get_bits_count(gbc);
+
+    w = av_log2(n) + 1;
+    m = (1 << w) - n;
+
+    if (get_bits_left(gbc) < w) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid non-symmetric value at "
+               "%s: bitstream ended.\n", name);
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (w - 1 > 0)
+        v = get_bits(gbc, w - 1);
+    else
+        v = 0;
+
+    if (v < m) {
+        value = v;
+    } else {
+        extra_bit = get_bits1(gbc);
+        value = (v << 1) - m + extra_bit;
+    }
+
+    if (ctx->trace_enable) {
+        char bits[33];
+        int i;
+        for (i = 0; i < w - 1; i++)
+            bits[i] = (v >> i & 1) ? '1' : '0';
+        if (v >= m)
+            bits[i++] = extra_bit ? '1' : '0';
+        bits[i] = 0;
+
+        ff_cbs_trace_syntax_element(ctx, position,
+                                    name, subscripts, bits, value);
+    }
+
+    *write_to = value;
+    return 0;
+}
+
+static int cbs_av1_write_ns(CodedBitstreamContext *ctx, PutBitContext *pbc,
+                            uint32_t n, const char *name,
+                            const int *subscripts, uint32_t value)
+{
+    uint32_t w, m, v, extra_bit;
+    int position;
+
+    if (value > n) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "%s out of range: "
+               "%"PRIu32", but must be in [0,%"PRIu32"].\n",
+               name, value, n);
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (ctx->trace_enable)
+        position = put_bits_count(pbc);
+
+    w = av_log2(n) + 1;
+    m = (1 << w) - n;
+
+    if (put_bits_left(pbc) < w)
+        return AVERROR(ENOSPC);
+
+    if (value < m) {
+        v = value;
+        put_bits(pbc, w - 1, v);
+    } else {
+        v = m + ((value - m) >> 1);
+        extra_bit = (value - m) & 1;
+        put_bits(pbc, w - 1, v);
+        put_bits(pbc, 1, extra_bit);
+    }
+
+    if (ctx->trace_enable) {
+        char bits[33];
+        int i;
+        for (i = 0; i < w - 1; i++)
+            bits[i] = (v >> i & 1) ? '1' : '0';
+        if (value >= m)
+            bits[i++] = extra_bit ? '1' : '0';
+        bits[i] = 0;
+
+        ff_cbs_trace_syntax_element(ctx, position,
+                                    name, subscripts, bits, value);
+    }
+
+    return 0;
+}
+
+static int cbs_av1_read_increment(CodedBitstreamContext *ctx, GetBitContext *gbc,
+                                  uint32_t range_min, uint32_t range_max,
+                                  const char *name, uint32_t *write_to)
+{
+    uint32_t value;
+    int position, i;
+    char bits[33];
+
+    av_assert0(range_min <= range_max && range_max - range_min < sizeof(bits) - 1);
+    if (ctx->trace_enable)
+        position = get_bits_count(gbc);
+
+    for (i = 0, value = range_min; value < range_max;) {
+        if (get_bits_left(gbc) < 1) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid increment value at "
+                   "%s: bitstream ended.\n", name);
+            return AVERROR_INVALIDDATA;
+        }
+        if (get_bits1(gbc)) {
+            bits[i++] = '1';
+            ++value;
+        } else {
+            bits[i++] = '0';
+            break;
+        }
+    }
+
+    if (ctx->trace_enable) {
+        bits[i] = 0;
+        ff_cbs_trace_syntax_element(ctx, position,
+                                    name, NULL, bits, value);
+    }
+
+    *write_to = value;
+    return 0;
+}
+
+static int cbs_av1_write_increment(CodedBitstreamContext *ctx, PutBitContext *pbc,
+                                   uint32_t range_min, uint32_t range_max,
+                                   const char *name, uint32_t value)
+{
+    int len;
+
+    av_assert0(range_min <= range_max && range_max - range_min < 32);
+    if (value < range_min || value > range_max) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "%s out of range: "
+               "%"PRIu32", but must be in [%"PRIu32",%"PRIu32"].\n",
+               name, value, range_min, range_max);
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (value == range_max)
+        len = range_max - range_min;
+    else
+        len = value - range_min + 1;
+    if (put_bits_left(pbc) < len)
+        return AVERROR(ENOSPC);
+
+    if (ctx->trace_enable) {
+        char bits[33];
+        int i;
+        for (i = 0; i < len; i++) {
+            if (range_min + i == value)
+                bits[i] = '0';
+            else
+                bits[i] = '1';
+        }
+        bits[i] = 0;
+        ff_cbs_trace_syntax_element(ctx, put_bits_count(pbc),
+                                    name, NULL, bits, value);
+    }
+
+    if (len > 0)
+        put_bits(pbc, len, (1 << len) - 1 - (value != range_max));
+
+    return 0;
+}
+
+static int cbs_av1_read_subexp(CodedBitstreamContext *ctx, GetBitContext *gbc,
+                               uint32_t range_max, const char *name,
+                               const int *subscripts, uint32_t *write_to)
+{
+    uint32_t value;
+    int position, err;
+    uint32_t max_len, len, range_offset, range_bits;
+
+    if (ctx->trace_enable)
+        position = get_bits_count(gbc);
+
+    av_assert0(range_max > 0);
+    max_len = av_log2(range_max - 1) - 3;
+
+    err = cbs_av1_read_increment(ctx, gbc, 0, max_len,
+                                 "subexp_more_bits", &len);
+    if (err < 0)
+        return err;
+
+    if (len) {
+        range_bits   = 2 + len;
+        range_offset = 1 << range_bits;
+    } else {
+        range_bits   = 3;
+        range_offset = 0;
+    }
+
+    if (len < max_len) {
+        err = ff_cbs_read_unsigned(ctx, gbc, range_bits,
+                                   "subexp_bits", NULL, &value,
+                                   0, MAX_UINT_BITS(range_bits));
+        if (err < 0)
+            return err;
+
+    } else {
+        err = cbs_av1_read_ns(ctx, gbc, range_max - range_offset,
+                              "subexp_final_bits", NULL, &value);
+        if (err < 0)
+            return err;
+    }
+    value += range_offset;
+
+    if (ctx->trace_enable)
+        ff_cbs_trace_syntax_element(ctx, position,
+                                    name, subscripts, "", value);
+
+    *write_to = value;
+    return err;
+}
+
+static int cbs_av1_write_subexp(CodedBitstreamContext *ctx, PutBitContext *pbc,
+                                uint32_t range_max, const char *name,
+                                const int *subscripts, uint32_t value)
+{
+    int position, err;
+    uint32_t max_len, len, range_offset, range_bits;
+
+    if (value > range_max) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "%s out of range: "
+               "%"PRIu32", but must be in [0,%"PRIu32"].\n",
+               name, value, range_max);
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (ctx->trace_enable)
+        position = put_bits_count(pbc);
+
+    av_assert0(range_max > 0);
+    max_len = av_log2(range_max - 1) - 3;
+
+    if (value < 8) {
+        range_bits   = 3;
+        range_offset = 0;
+        len = 0;
+    } else {
+        range_bits = av_log2(value);
+        len = range_bits - 2;
+        if (len > max_len) {
+            // The top bin is combined with the one below it.
+            av_assert0(len == max_len + 1);
+            --range_bits;
+            len = max_len;
+        }
+        range_offset = 1 << range_bits;
+    }
+
+    err = cbs_av1_write_increment(ctx, pbc, 0, max_len,
+                                  "subexp_more_bits", len);
+    if (err < 0)
+        return err;
+
+    if (len < max_len) {
+        err = ff_cbs_write_unsigned(ctx, pbc, range_bits,
+                                    "subexp_bits", NULL,
+                                    value - range_offset,
+                                    0, MAX_UINT_BITS(range_bits));
+        if (err < 0)
+            return err;
+
+    } else {
+        err = cbs_av1_write_ns(ctx, pbc, range_max - range_offset,
+                               "subexp_final_bits", NULL,
+                               value - range_offset);
+        if (err < 0)
+            return err;
+    }
+
+    if (ctx->trace_enable)
+        ff_cbs_trace_syntax_element(ctx, position,
+                                    name, subscripts, "", value);
+
+    return err;
+}
+
+
+static int cbs_av1_tile_log2(int blksize, int target)
+{
+    int k;
+    for (k = 0; (blksize << k) < target; k++);
+    return k;
+}
+
+static int cbs_av1_get_relative_dist(const AV1RawSequenceHeader *seq,
+                                     unsigned int a, unsigned int b)
+{
+    unsigned int diff, m;
+    if (!seq->enable_order_hint)
+        return 0;
+    diff = a - b;
+    m = 1 << seq->order_hint_bits_minus_1;
+    diff = (diff & (m - 1)) - (diff & m);
+    return diff;
+}
+
+
+#define HEADER(name) do { \
+        ff_cbs_trace_header(ctx, name); \
+    } while (0)
+
+#define CHECK(call) do { \
+        err = (call); \
+        if (err < 0) \
+            return err; \
+    } while (0)
+
+#define FUNC_NAME(rw, codec, name) cbs_ ## codec ## _ ## rw ## _ ## name
+#define FUNC_AV1(rw, name) FUNC_NAME(rw, av1, name)
+#define FUNC(name) FUNC_AV1(READWRITE, name)
+
+#define SUBSCRIPTS(subs, ...) (subs > 0 ? ((int[subs + 1]){ subs, __VA_ARGS__ }) : NULL)
+
+#define fb(width, name) \
+        xf(width, name, current->name, 0, MAX_UINT_BITS(width), 0)
+#define fc(width, name, range_min, range_max) \
+        xf(width, name, current->name, range_min, range_max, 0)
+#define flag(name) fb(1, name)
+#define su(width, name) \
+        xsu(width, name, current->name, 0)
+
+#define fbs(width, name, subs, ...) \
+        xf(width, name, current->name, 0, MAX_UINT_BITS(width), subs, __VA_ARGS__)
+#define fcs(width, name, range_min, range_max, subs, ...) \
+        xf(width, name, current->name, range_min, range_max, subs, __VA_ARGS__)
+#define flags(name, subs, ...) \
+        xf(1, name, current->name, 0, 1, subs, __VA_ARGS__)
+#define sus(width, name, subs, ...) \
+        xsu(width, name, current->name, subs, __VA_ARGS__)
+
+#define fixed(width, name, value) do { \
+        av_unused uint32_t fixed_value = value; \
+        xf(width, name, fixed_value, value, value, 0); \
+    } while (0)
+
+
+#define READ
+#define READWRITE read
+#define RWContext GetBitContext
+
+#define xf(width, name, var, range_min, range_max, subs, ...) do { \
+        uint32_t value = range_min; \
+        CHECK(ff_cbs_read_unsigned(ctx, rw, width, #name, \
+                                   SUBSCRIPTS(subs, __VA_ARGS__), \
+                                   &value, range_min, range_max)); \
+        var = value; \
+    } while (0)
+
+#define xsu(width, name, var, subs, ...) do { \
+        int32_t value = 0; \
+        CHECK(cbs_av1_read_su(ctx, rw, width, #name, \
+                              SUBSCRIPTS(subs, __VA_ARGS__), &value)); \
+        var = value; \
+    } while (0)
+
+#define uvlc(name, range_min, range_max) do { \
+        uint32_t value = range_min; \
+        CHECK(cbs_av1_read_uvlc(ctx, rw, #name, \
+                                &value, range_min, range_max)); \
+        current->name = value; \
+    } while (0)
+
+#define ns(max_value, name, subs, ...) do { \
+        uint32_t value = 0; \
+        CHECK(cbs_av1_read_ns(ctx, rw, max_value, #name, \
+                              SUBSCRIPTS(subs, __VA_ARGS__), &value)); \
+        current->name = value; \
+    } while (0)
+
+#define increment(name, min, max) do { \
+        uint32_t value = 0; \
+        CHECK(cbs_av1_read_increment(ctx, rw, min, max, #name, &value)); \
+        current->name = value; \
+    } while (0)
+
+#define subexp(name, max, subs, ...) do { \
+        uint32_t value = 0; \
+        CHECK(cbs_av1_read_subexp(ctx, rw, max, #name, \
+                                  SUBSCRIPTS(subs, __VA_ARGS__), &value)); \
+        current->name = value; \
+    } while (0)
+
+#define delta_q(name) do { \
+        uint8_t delta_coded; \
+        int8_t delta_q; \
+        xf(1, name.delta_coded, delta_coded, 0, 1, 0); \
+        if (delta_coded) \
+            xsu(1 + 6, name.delta_q, delta_q, 0); \
+        else \
+            delta_q = 0; \
+        current->name = delta_q; \
+    } while (0)
+
+#define leb128(name) do { \
+        uint64_t value = 0; \
+        CHECK(cbs_av1_read_leb128(ctx, rw, #name, &value)); \
+        current->name = value; \
+    } while (0)
+
+#define infer(name, value) do { \
+        current->name = value; \
+    } while (0)
+
+#define byte_alignment(rw) (get_bits_count(rw) % 8)
+
+#include "cbs_av1_syntax_template.c"
+
+#undef READ
+#undef READWRITE
+#undef RWContext
+#undef xf
+#undef xsu
+#undef uvlc
+#undef leb128
+#undef ns
+#undef increment
+#undef subexp
+#undef delta_q
+#undef leb128
+#undef infer
+#undef byte_alignment
+
+
+#define WRITE
+#define READWRITE write
+#define RWContext PutBitContext
+
+#define xf(width, name, var, range_min, range_max, subs, ...) do { \
+        CHECK(ff_cbs_write_unsigned(ctx, rw, width, #name, \
+                                    SUBSCRIPTS(subs, __VA_ARGS__), \
+                                    var, range_min, range_max)); \
+    } while (0)
+
+#define xsu(width, name, var, subs, ...) do { \
+        CHECK(cbs_av1_write_su(ctx, rw, width, #name, \
+                               SUBSCRIPTS(subs, __VA_ARGS__), var)); \
+    } while (0)
+
+#define uvlc(name, range_min, range_max) do { \
+        CHECK(cbs_av1_write_uvlc(ctx, rw, #name, current->name, \
+                                 range_min, range_max)); \
+    } while (0)
+
+#define ns(max_value, name, subs, ...) do { \
+        CHECK(cbs_av1_write_ns(ctx, rw, max_value, #name, \
+                               SUBSCRIPTS(subs, __VA_ARGS__), \
+                               current->name)); \
+    } while (0)
+
+#define increment(name, min, max) do { \
+        CHECK(cbs_av1_write_increment(ctx, rw, min, max, #name, \
+                                      current->name)); \
+    } while (0)
+
+#define subexp(name, max, subs, ...) do { \
+        CHECK(cbs_av1_write_subexp(ctx, rw, max, #name, \
+                                   SUBSCRIPTS(subs, __VA_ARGS__), \
+                                   current->name)); \
+    } while (0)
+
+#define delta_q(name) do { \
+        xf(1, name.delta_coded, current->name != 0, 0, 1, 0); \
+        if (current->name) \
+            xsu(1 + 6, name.delta_q, current->name, 0); \
+    } while (0)
+
+#define leb128(name) do { \
+        CHECK(cbs_av1_write_leb128(ctx, rw, #name, current->name)); \
+    } while (0)
+
+#define infer(name, value) do { \
+        if (current->name != (value)) { \
+            av_log(ctx->log_ctx, AV_LOG_WARNING, "Warning: " \
+                   "%s does not match inferred value: " \
+                   "%"PRId64", but should be %"PRId64".\n", \
+                   #name, (int64_t)current->name, (int64_t)(value)); \
+        } \
+    } while (0)
+
+#define byte_alignment(rw) (put_bits_count(rw) % 8)
+
+#include "cbs_av1_syntax_template.c"
+
+#undef READ
+#undef READWRITE
+#undef RWContext
+#undef xf
+#undef xsu
+#undef uvlc
+#undef leb128
+#undef ns
+#undef increment
+#undef subexp
+#undef delta_q
+#undef infer
+#undef byte_alignment
+
+
+static int cbs_av1_split_fragment(CodedBitstreamContext *ctx,
+                                  CodedBitstreamFragment *frag,
+                                  int header)
+{
+    GetBitContext gbc;
+    uint8_t *data;
+    size_t size;
+    uint64_t obu_length;
+    int pos, err, trace;
+
+    // Don't include this parsing in trace output.
+    trace = ctx->trace_enable;
+    ctx->trace_enable = 0;
+
+    data = frag->data;
+    size = frag->data_size;
+
+    if (INT_MAX / 8 < size) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid fragment: "
+               "too large (%zu bytes).\n", size);
+        err = AVERROR_INVALIDDATA;
+        goto fail;
+    }
+
+    while (size > 0) {
+        AV1RawOBUHeader header;
+        uint64_t obu_size;
+
+        init_get_bits(&gbc, data, 8 * size);
+
+        err = cbs_av1_read_obu_header(ctx, &gbc, &header);
+        if (err < 0)
+            goto fail;
+
+        if (!header.obu_has_size_field) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid OBU for raw "
+                   "stream: size field must be present.\n");
+            err = AVERROR_INVALIDDATA;
+            goto fail;
+        }
+
+        if (get_bits_left(&gbc) < 8) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid OBU: fragment "
+                   "too short (%zu bytes).\n", size);
+            err = AVERROR_INVALIDDATA;
+            goto fail;
+        }
+
+        err = cbs_av1_read_leb128(ctx, &gbc, "obu_size", &obu_size);
+        if (err < 0)
+            goto fail;
+
+        pos = get_bits_count(&gbc);
+        av_assert0(pos % 8 == 0 && pos / 8 <= size);
+
+        obu_length = pos / 8 + obu_size;
+
+        if (size < obu_length) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid OBU length: "
+                   "%"PRIu64", but only %zu bytes remaining in fragment.\n",
+                   obu_length, size);
+            err = AVERROR_INVALIDDATA;
+            goto fail;
+        }
+
+        err = ff_cbs_insert_unit_data(ctx, frag, -1, header.obu_type,
+                                      data, obu_length, frag->data_ref);
+        if (err < 0)
+            goto fail;
+
+        data += obu_length;
+        size -= obu_length;
+    }
+
+    err = 0;
+fail:
+    ctx->trace_enable = trace;
+    return err;
+}
+
+static void cbs_av1_free_tile_data(AV1RawTileData *td)
+{
+    av_buffer_unref(&td->data_ref);
+}
+
+static void cbs_av1_free_metadata(AV1RawMetadata *md)
+{
+    switch (md->metadata_type) {
+    case AV1_METADATA_TYPE_ITUT_T35:
+        av_buffer_unref(&md->metadata.itut_t35.payload_ref);
+        break;
+    }
+}
+
+static void cbs_av1_free_obu(void *unit, uint8_t *content)
+{
+    AV1RawOBU *obu = (AV1RawOBU*)content;
+
+    switch (obu->header.obu_type) {
+    case AV1_OBU_TILE_GROUP:
+        cbs_av1_free_tile_data(&obu->obu.tile_group.tile_data);
+        break;
+    case AV1_OBU_FRAME:
+        cbs_av1_free_tile_data(&obu->obu.frame.tile_group.tile_data);
+        break;
+    case AV1_OBU_TILE_LIST:
+        cbs_av1_free_tile_data(&obu->obu.tile_list.tile_data);
+        break;
+    case AV1_OBU_METADATA:
+        cbs_av1_free_metadata(&obu->obu.metadata);
+        break;
+    }
+
+    av_freep(&obu);
+}
+
+static int cbs_av1_ref_tile_data(CodedBitstreamContext *ctx,
+                                 CodedBitstreamUnit *unit,
+                                 GetBitContext *gbc,
+                                 AV1RawTileData *td)
+{
+    int pos;
+
+    pos = get_bits_count(gbc);
+    if (pos >= 8 * unit->data_size) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Bitstream ended before "
+               "any data in tile group (%d bits read).\n", pos);
+        return AVERROR_INVALIDDATA;
+    }
+    // Must be byte-aligned at this point.
+    av_assert0(pos % 8 == 0);
+
+    td->data_ref = av_buffer_ref(unit->data_ref);
+    if (!td->data_ref)
+        return AVERROR(ENOMEM);
+
+    td->data      = unit->data      + pos / 8;
+    td->data_size = unit->data_size - pos / 8;
+
+    return 0;
+}
+
+static int cbs_av1_read_unit(CodedBitstreamContext *ctx,
+                             CodedBitstreamUnit *unit)
+{
+    CodedBitstreamAV1Context *priv = ctx->priv_data;
+    AV1RawOBU *obu;
+    GetBitContext gbc;
+    int err, start_pos, end_pos;
+
+    err = ff_cbs_alloc_unit_content(ctx, unit, sizeof(*obu),
+                                    &cbs_av1_free_obu);
+    if (err < 0)
+        return err;
+    obu = unit->content;
+
+    err = init_get_bits(&gbc, unit->data, 8 * unit->data_size);
+    if (err < 0)
+        return err;
+
+    err = cbs_av1_read_obu_header(ctx, &gbc, &obu->header);
+    if (err < 0)
+        return err;
+    av_assert0(obu->header.obu_type == unit->type);
+
+    if (obu->header.obu_has_size_field) {
+        uint64_t obu_size;
+        err = cbs_av1_read_leb128(ctx, &gbc, "obu_size", &obu_size);
+        if (err < 0)
+            return err;
+        obu->obu_size = obu_size;
+    } else {
+        if (unit->data_size < 1 + obu->header.obu_extension_flag) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid OBU length: "
+                   "unit too short (%zu).\n", unit->data_size);
+            return AVERROR_INVALIDDATA;
+        }
+        obu->obu_size = unit->data_size - 1 - obu->header.obu_extension_flag;
+    }
+
+    start_pos = get_bits_count(&gbc);
+
+    if (obu->header.obu_extension_flag) {
+        priv->temporal_id = obu->header.temporal_id;
+        priv->spatial_id  = obu->header.temporal_id;
+
+        if (obu->header.obu_type != AV1_OBU_SEQUENCE_HEADER &&
+            obu->header.obu_type != AV1_OBU_TEMPORAL_DELIMITER &&
+            priv->operating_point_idc) {
+            int in_temporal_layer =
+                (priv->operating_point_idc >>  priv->temporal_id    ) & 1;
+            int in_spatial_layer  =
+                (priv->operating_point_idc >> (priv->spatial_id + 8)) & 1;
+            if (!in_temporal_layer || !in_spatial_layer) {
+                // Decoding will drop this OBU at this operating point.
+            }
+        }
+    } else {
+        priv->temporal_id = 0;
+        priv->spatial_id  = 0;
+    }
+
+    switch (obu->header.obu_type) {
+    case AV1_OBU_SEQUENCE_HEADER:
+        {
+            err = cbs_av1_read_sequence_header_obu(ctx, &gbc,
+                                                   &obu->obu.sequence_header);
+            if (err < 0)
+                return err;
+
+            av_buffer_unref(&priv->sequence_header_ref);
+            priv->sequence_header = NULL;
+
+            priv->sequence_header_ref = av_buffer_ref(unit->content_ref);
+            if (!priv->sequence_header_ref)
+                return AVERROR(ENOMEM);
+            priv->sequence_header = &obu->obu.sequence_header;
+        }
+        break;
+    case AV1_OBU_TEMPORAL_DELIMITER:
+        {
+            err = cbs_av1_read_temporal_delimiter_obu(ctx, &gbc);
+            if (err < 0)
+                return err;
+        }
+        break;
+    case AV1_OBU_FRAME_HEADER:
+    case AV1_OBU_REDUNDANT_FRAME_HEADER:
+        {
+            err = cbs_av1_read_frame_header_obu(ctx, &gbc,
+                                                &obu->obu.frame_header);
+            if (err < 0)
+                return err;
+        }
+        break;
+    case AV1_OBU_TILE_GROUP:
+        {
+            err = cbs_av1_read_tile_group_obu(ctx, &gbc,
+                                              &obu->obu.tile_group);
+            if (err < 0)
+                return err;
+
+            err = cbs_av1_ref_tile_data(ctx, unit, &gbc,
+                                        &obu->obu.tile_group.tile_data);
+            if (err < 0)
+                return err;
+        }
+        break;
+    case AV1_OBU_FRAME:
+        {
+            err = cbs_av1_read_frame_obu(ctx, &gbc, &obu->obu.frame);
+            if (err < 0)
+                return err;
+
+            err = cbs_av1_ref_tile_data(ctx, unit, &gbc,
+                                        &obu->obu.frame.tile_group.tile_data);
+            if (err < 0)
+                return err;
+        }
+        break;
+    case AV1_OBU_TILE_LIST:
+        {
+            err = cbs_av1_read_tile_list_obu(ctx, &gbc,
+                                             &obu->obu.tile_list);
+            if (err < 0)
+                return err;
+
+            err = cbs_av1_ref_tile_data(ctx, unit, &gbc,
+                                        &obu->obu.tile_list.tile_data);
+            if (err < 0)
+                return err;
+        }
+        break;
+    case AV1_OBU_METADATA:
+        {
+            err = cbs_av1_read_metadata_obu(ctx, &gbc, &obu->obu.metadata);
+            if (err < 0)
+                return err;
+        }
+        break;
+    case AV1_OBU_PADDING:
+    default:
+        return AVERROR(ENOSYS);
+    }
+
+    end_pos = get_bits_count(&gbc);
+    av_assert0(end_pos <= unit->data_size * 8);
+
+    if (obu->obu_size > 0 &&
+        obu->header.obu_type != AV1_OBU_TILE_GROUP &&
+        obu->header.obu_type != AV1_OBU_FRAME) {
+        err = cbs_av1_read_trailing_bits(ctx, &gbc,
+                                         obu->obu_size * 8 + start_pos - end_pos);
+        if (err < 0)
+            return err;
+    }
+
+    return 0;
+}
+
+static int cbs_av1_write_obu(CodedBitstreamContext *ctx,
+                             CodedBitstreamUnit *unit,
+                             PutBitContext *pbc)
+{
+    CodedBitstreamAV1Context *priv = ctx->priv_data;
+    AV1RawOBU *obu = unit->content;
+    PutBitContext pbc_tmp;
+    AV1RawTileData *td;
+    size_t header_size;
+    int err, start_pos, end_pos, data_pos;
+
+    // OBUs in the normal bitstream format must contain a size field
+    // in every OBU (in annex B it is optional, but we don't support
+    // writing that).
+    obu->header.obu_has_size_field = 1;
+
+    err = cbs_av1_write_obu_header(ctx, pbc, &obu->header);
+    if (err < 0)
+        return err;
+
+    if (obu->header.obu_has_size_field) {
+        pbc_tmp = *pbc;
+        // Add space for the size field to fill later.
+        put_bits32(pbc, 0);
+        put_bits32(pbc, 0);
+    }
+
+    td = NULL;
+    start_pos = put_bits_count(pbc);
+
+    switch (obu->header.obu_type) {
+    case AV1_OBU_SEQUENCE_HEADER:
+        {
+            err = cbs_av1_write_sequence_header_obu(ctx, pbc,
+                                                    &obu->obu.sequence_header);
+            if (err < 0)
+                return err;
+
+            av_buffer_unref(&priv->sequence_header_ref);
+            priv->sequence_header = NULL;
+
+            priv->sequence_header_ref = av_buffer_ref(unit->content_ref);
+            if (!priv->sequence_header_ref)
+                return AVERROR(ENOMEM);
+            priv->sequence_header = &obu->obu.sequence_header;
+        }
+        break;
+    case AV1_OBU_TEMPORAL_DELIMITER:
+        {
+            err = cbs_av1_write_temporal_delimiter_obu(ctx, pbc);
+            if (err < 0)
+                return err;
+        }
+        break;
+    case AV1_OBU_FRAME_HEADER:
+    case AV1_OBU_REDUNDANT_FRAME_HEADER:
+        {
+            err = cbs_av1_write_frame_header_obu(ctx, pbc,
+                                                 &obu->obu.frame_header);
+            if (err < 0)
+                return err;
+        }
+        break;
+    case AV1_OBU_TILE_GROUP:
+        {
+            err = cbs_av1_write_tile_group_obu(ctx, pbc,
+                                               &obu->obu.tile_group);
+            if (err < 0)
+                return err;
+
+            td = &obu->obu.tile_group.tile_data;
+        }
+        break;
+    case AV1_OBU_FRAME:
+        {
+            err = cbs_av1_write_frame_obu(ctx, pbc, &obu->obu.frame);
+            if (err < 0)
+                return err;
+
+            td = &obu->obu.frame.tile_group.tile_data;
+        }
+        break;
+    case AV1_OBU_TILE_LIST:
+        {
+            err = cbs_av1_write_tile_list_obu(ctx, pbc, &obu->obu.tile_list);
+            if (err < 0)
+                return err;
+
+            td = &obu->obu.tile_list.tile_data;
+        }
+        break;
+    case AV1_OBU_METADATA:
+        {
+            err = cbs_av1_write_metadata_obu(ctx, pbc, &obu->obu.metadata);
+            if (err < 0)
+                return err;
+        }
+        break;
+    case AV1_OBU_PADDING:
+    default:
+        return AVERROR(ENOSYS);
+    }
+
+    end_pos = put_bits_count(pbc);
+    header_size = (end_pos - start_pos + 7) / 8;
+    if (td) {
+        obu->obu_size = header_size + td->data_size;
+    } else if (header_size > 0) {
+        // Add trailing bits and recalculate.
+        err = cbs_av1_write_trailing_bits(ctx, pbc, 8 - end_pos % 8);
+        if (err < 0)
+            return err;
+        end_pos = put_bits_count(pbc);
+        obu->obu_size = (end_pos - start_pos + 7) / 8;
+    } else {
+        // Empty OBU.
+        obu->obu_size = 0;
+    }
+
+    end_pos = put_bits_count(pbc);
+    // Must now be byte-aligned.
+    av_assert0(end_pos % 8 == 0);
+    flush_put_bits(pbc);
+    start_pos /= 8;
+    end_pos   /= 8;
+
+    *pbc = pbc_tmp;
+    err = cbs_av1_write_leb128(ctx, pbc, "obu_size", obu->obu_size);
+    if (err < 0)
+        return err;
+
+    data_pos = put_bits_count(pbc) / 8;
+    flush_put_bits(pbc);
+    av_assert0(data_pos <= start_pos);
+
+    if (8 * obu->obu_size > put_bits_left(pbc))
+        return AVERROR(ENOSPC);
+
+    if (obu->obu_size > 0) {
+        memmove(priv->write_buffer + data_pos,
+                priv->write_buffer + start_pos, header_size);
+        skip_put_bytes(pbc, header_size);
+
+        if (td) {
+            memcpy(priv->write_buffer + data_pos + header_size,
+                   td->data, td->data_size);
+            skip_put_bytes(pbc, td->data_size);
+        }
+    }
+
+    return 0;
+}
+
+static int cbs_av1_write_unit(CodedBitstreamContext *ctx,
+                              CodedBitstreamUnit *unit)
+{
+    CodedBitstreamAV1Context *priv = ctx->priv_data;
+    PutBitContext pbc;
+    int err;
+
+    if (!priv->write_buffer) {
+        // Initial write buffer size is 1MB.
+        priv->write_buffer_size = 1024 * 1024;
+
+    reallocate_and_try_again:
+        err = av_reallocp(&priv->write_buffer, priv->write_buffer_size);
+        if (err < 0) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Unable to allocate a "
+                   "sufficiently large write buffer (last attempt "
+                   "%zu bytes).\n", priv->write_buffer_size);
+            return err;
+        }
+    }
+
+    init_put_bits(&pbc, priv->write_buffer, priv->write_buffer_size);
+
+    err = cbs_av1_write_obu(ctx, unit, &pbc);
+    if (err == AVERROR(ENOSPC)) {
+        // Overflow.
+        priv->write_buffer_size *= 2;
+        goto reallocate_and_try_again;
+    }
+    if (err < 0)
+        return err;
+
+    // Overflow but we didn't notice.
+    av_assert0(put_bits_count(&pbc) <= 8 * priv->write_buffer_size);
+
+    // OBU data must be byte-aligned.
+    av_assert0(put_bits_count(&pbc) % 8 == 0);
+
+    unit->data_size = put_bits_count(&pbc) / 8;
+    flush_put_bits(&pbc);
+
+    err = ff_cbs_alloc_unit_data(ctx, unit, unit->data_size);
+    if (err < 0)
+        return err;
+
+    memcpy(unit->data, priv->write_buffer, unit->data_size);
+
+    return 0;
+}
+
+static int cbs_av1_assemble_fragment(CodedBitstreamContext *ctx,
+                                     CodedBitstreamFragment *frag)
+{
+    size_t size, pos;
+    int i;
+
+    size = 0;
+    for (i = 0; i < frag->nb_units; i++)
+        size += frag->units[i].data_size;
+
+    frag->data_ref = av_buffer_alloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
+    if (!frag->data_ref)
+        return AVERROR(ENOMEM);
+    frag->data = frag->data_ref->data;
+    memset(frag->data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
+
+    pos = 0;
+    for (i = 0; i < frag->nb_units; i++) {
+        memcpy(frag->data + pos, frag->units[i].data,
+               frag->units[i].data_size);
+        pos += frag->units[i].data_size;
+    }
+    av_assert0(pos == size);
+    frag->data_size = size;
+
+    return 0;
+}
+
+static void cbs_av1_close(CodedBitstreamContext *ctx)
+{
+    CodedBitstreamAV1Context *priv = ctx->priv_data;
+
+    av_buffer_unref(&priv->sequence_header_ref);
+
+    av_freep(&priv->write_buffer);
+}
+
+const CodedBitstreamType ff_cbs_type_av1 = {
+    .codec_id          = AV_CODEC_ID_AV1,
+
+    .priv_data_size    = sizeof(CodedBitstreamAV1Context),
+
+    .split_fragment    = &cbs_av1_split_fragment,
+    .read_unit         = &cbs_av1_read_unit,
+    .write_unit        = &cbs_av1_write_unit,
+    .assemble_fragment = &cbs_av1_assemble_fragment,
+
+    .close             = &cbs_av1_close,
+};
diff --git a/libavcodec/cbs_av1.h b/libavcodec/cbs_av1.h
new file mode 100644
index 0000000000..0d7fd761f1
--- /dev/null
+++ b/libavcodec/cbs_av1.h
@@ -0,0 +1,429 @@
+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVCODEC_CBS_AV1_H
+#define AVCODEC_CBS_AV1_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "av1.h"
+#include "cbs.h"
+
+
+typedef struct AV1RawOBUHeader {
+    uint8_t obu_forbidden_bit;
+    uint8_t obu_type;
+    uint8_t obu_extension_flag;
+    uint8_t obu_has_size_field;
+    uint8_t obu_reserved_1bit;
+
+    uint8_t temporal_id;
+    uint8_t spatial_id;
+    uint8_t extension_header_reserved_3bits;
+} AV1RawOBUHeader;
+
+typedef struct AV1RawColorConfig {
+    uint8_t high_bitdepth;
+    uint8_t twelve_bit;
+    uint8_t mono_chrome;
+
+    uint8_t color_description_present_flag;
+    uint8_t color_primaries;
+    uint8_t transfer_characteristics;
+    uint8_t matrix_coefficients;
+
+    uint8_t color_range;
+    uint8_t subsampling_x;
+    uint8_t subsampling_y;
+    uint8_t chroma_sample_position;
+    uint8_t separate_uv_delta_q;
+} AV1RawColorConfig;
+
+typedef struct AV1RawTimingInfo {
+    uint32_t num_units_in_display_tick;
+    uint32_t time_scale;
+
+    uint8_t equal_picture_interval;
+    uint32_t num_ticks_per_picture_minus_1;
+} AV1RawTimingInfo;
+
+typedef struct AV1RawDecoderModelInfo {
+    uint8_t  buffer_delay_length_minus_1;
+    uint32_t num_units_in_decoding_tick;
+    uint8_t  buffer_removal_time_length_minus_1;
+    uint8_t  frame_presentation_time_length_minus_1;
+} AV1RawDecoderModelInfo;
+
+typedef struct AV1RawSequenceHeader {
+    uint8_t seq_profile;
+    uint8_t still_picture;
+    uint8_t reduced_still_picture_header;
+
+    uint8_t timing_info_present_flag;
+    uint8_t decoder_model_info_present_flag;
+    uint8_t initial_display_delay_present_flag;
+    uint8_t operating_points_cnt_minus_1;
+
+    AV1RawTimingInfo       timing_info;
+    AV1RawDecoderModelInfo decoder_model_info;
+
+    uint16_t operating_point_idc[AV1_MAX_OPERATING_POINTS];
+    uint8_t  seq_level_idx[AV1_MAX_OPERATING_POINTS];
+    uint8_t  seq_tier[AV1_MAX_OPERATING_POINTS];
+    uint8_t  decoder_model_present_for_this_op[AV1_MAX_OPERATING_POINTS];
+    uint8_t  decoder_buffer_delay[AV1_MAX_OPERATING_POINTS];
+    uint8_t  encoder_buffer_delay[AV1_MAX_OPERATING_POINTS];
+    uint8_t  low_delay_mode_flag[AV1_MAX_OPERATING_POINTS];
+    uint8_t  initial_display_delay_present_for_this_op[AV1_MAX_OPERATING_POINTS];
+    uint8_t  initial_display_delay_minus_1[AV1_MAX_OPERATING_POINTS];
+
+    uint8_t  frame_width_bits_minus_1;
+    uint8_t  frame_height_bits_minus_1;
+    uint16_t max_frame_width_minus_1;
+    uint16_t max_frame_height_minus_1;
+
+    uint8_t frame_id_numbers_present_flag;
+    uint8_t delta_frame_id_length_minus_2;
+    uint8_t additional_frame_id_length_minus_1;
+
+    uint8_t use_128x128_superblock;
+    uint8_t enable_filter_intra;
+    uint8_t enable_intra_edge_filter;
+    uint8_t enable_intraintra_compound;
+    uint8_t enable_masked_compound;
+    uint8_t enable_warped_motion;
+    uint8_t enable_dual_filter;
+
+    uint8_t enable_order_hint;
+    uint8_t enable_jnt_comp;
+    uint8_t enable_ref_frame_mvs;
+
+    uint8_t seq_choose_screen_content_tools;
+    uint8_t seq_force_screen_content_tools;
+    uint8_t seq_choose_integer_mv;
+    uint8_t seq_force_integer_mv;
+
+    uint8_t order_hint_bits_minus_1;
+
+    uint8_t enable_superres;
+    uint8_t enable_cdef;
+    uint8_t enable_restoration;
+
+    AV1RawColorConfig color_config;
+
+    uint8_t film_grain_params_present;
+} AV1RawSequenceHeader;
+
+typedef struct AV1RawFrameHeader {
+    uint8_t  show_existing_frame;
+    uint8_t  frame_to_show_map_idx;
+    uint32_t frame_presentation_time;
+    uint32_t display_frame_id;
+
+    uint8_t frame_type;
+    uint8_t show_frame;
+    uint8_t showable_frame;
+
+    uint8_t error_resilient_mode;
+    uint8_t disable_cdf_update;
+    uint8_t allow_screen_content_tools;
+    uint8_t force_integer_mv;
+
+    uint32_t current_frame_id;
+    uint8_t  frame_size_override_flag;
+    uint8_t  order_hint;
+
+    uint8_t  buffer_removal_time_present_flag;
+    uint32_t buffer_removal_time[AV1_MAX_OPERATING_POINTS];
+
+    uint8_t  primary_ref_frame;
+    uint16_t frame_width_minus_1;
+    uint16_t frame_height_minus_1;
+    uint8_t  use_superres;
+    uint8_t  coded_denom;
+    uint8_t  render_and_frame_size_different;
+    uint8_t  render_width_minus_1;
+    uint8_t  render_height_minus_1;
+
+    uint8_t found_ref;
+
+    uint8_t refresh_frame_flags;
+    uint8_t allow_intrabc;
+    uint8_t ref_order_hint[AV1_NUM_REF_FRAMES];
+    uint8_t frame_refs_short_signaling;
+    uint8_t last_frame_idx;
+    uint8_t golden_frame_idx;
+    int8_t  ref_frame_idx[AV1_REFS_PER_FRAME];
+    uint8_t delta_frame_id_minus1;
+
+    uint8_t allow_high_precision_mv;
+    uint8_t is_filter_switchable;
+    uint8_t interpolation_filter;
+    uint8_t is_motion_mode_switchable;
+    uint8_t use_ref_frame_mvs;
+
+    uint8_t disable_frame_end_update_cdf;
+
+    uint8_t uniform_tile_spacing_flag;
+    uint8_t tile_cols_log2;
+    uint8_t tile_rows_log2;
+    uint8_t width_in_sbs_minus_1[AV1_MAX_TILE_COLS];
+    uint8_t height_in_sbs_minus_1[AV1_MAX_TILE_ROWS];
+    uint16_t context_update_tile_id;
+    uint8_t tile_size_bytes_minus1;
+
+    // These are derived values, but it's very unhelpful to have to
+    // recalculate them all the time so we store them here.
+    uint16_t tile_cols;
+    uint16_t tile_rows;
+
+    uint8_t base_q_idx;
+    int8_t  delta_q_y_dc;
+    uint8_t diff_uv_delta;
+    int8_t  delta_q_u_dc;
+    int8_t  delta_q_u_ac;
+    int8_t  delta_q_v_dc;
+    int8_t  delta_q_v_ac;
+    uint8_t using_qmatrix;
+    uint8_t qm_y;
+    uint8_t qm_u;
+    uint8_t qm_v;
+
+    uint8_t segmentation_enabled;
+    uint8_t segmentation_update_map;
+    uint8_t segmentation_temporal_update;
+    uint8_t segmentation_update_data;
+    uint8_t feature_enabled[AV1_MAX_SEGMENTS][AV1_SEG_LVL_MAX];
+    uint8_t feature_value[AV1_MAX_SEGMENTS][AV1_SEG_LVL_MAX];
+
+    uint8_t delta_q_present;
+    uint8_t delta_q_res;
+    uint8_t delta_lf_present;
+    uint8_t delta_lf_res;
+    uint8_t delta_lf_multi;
+
+    uint8_t loop_filter_level[4];
+    uint8_t loop_filter_sharpness;
+    uint8_t loop_filter_delta_enabled;
+    uint8_t loop_filter_delta_update;
+    uint8_t update_ref_delta[AV1_TOTAL_REFS_PER_FRAME];
+    int8_t  loop_filter_ref_deltas[AV1_TOTAL_REFS_PER_FRAME];
+    uint8_t update_mode_delta[2];
+    int8_t  loop_filter_mode_deltas[2];
+
+    uint8_t cdef_damping_minus_3;
+    uint8_t cdef_bits;
+    uint8_t cdef_y_pri_strength[8];
+    uint8_t cdef_y_sec_strength[8];
+    uint8_t cdef_uv_pri_strength[8];
+    uint8_t cdef_uv_sec_strength[8];
+
+    uint8_t lr_type[3];
+    uint8_t lr_unit_shift;
+    uint8_t lr_uv_shift;
+
+    uint8_t tx_mode;
+    uint8_t reference_select;
+    uint8_t skip_mode_present;
+
+    uint8_t allow_warped_motion;
+    uint8_t reduced_tx_set;
+
+    uint8_t is_global[AV1_TOTAL_REFS_PER_FRAME];
+    uint8_t is_rot_zoom[AV1_TOTAL_REFS_PER_FRAME];
+    uint8_t is_translation[AV1_TOTAL_REFS_PER_FRAME];
+    //AV1RawSubexp gm_params[AV1_TOTAL_REFS_PER_FRAME][6];
+    uint32_t gm_params[AV1_TOTAL_REFS_PER_FRAME][6];
+
+    uint8_t  apply_grain;
+    uint16_t grain_seed;
+    uint8_t  update_grain;
+    uint8_t  film_grain_params_ref_idx;
+    uint8_t  num_y_points;
+    uint8_t  point_y_value[16];
+    uint8_t  point_y_scaling[16];
+    uint8_t  chroma_scaling_from_luma;
+    uint8_t  num_cb_points;
+    uint8_t  point_cb_value[16];
+    uint8_t  point_cb_scaling[16];
+    uint8_t  num_cr_points;
+    uint8_t  point_cr_value[16];
+    uint8_t  point_cr_scaling[16];
+    uint8_t  grain_scaling_minus_8;
+    uint8_t  ar_coeff_lag;
+    uint8_t  ar_coeffs_y_plus_128[24];
+    uint8_t  ar_coeffs_cb_plus_128[24];
+    uint8_t  ar_coeffs_cr_plus_128[24];
+    uint8_t  ar_coeff_shift_minus_6;
+    uint8_t  grain_scale_shift;
+    uint8_t  cb_mult;
+    uint8_t  cb_luma_mult;
+    uint16_t cb_offset;
+    uint8_t  cr_mult;
+    uint8_t  cr_luma_mult;
+    uint16_t cr_offset;
+    uint8_t  overlap_flag;
+    uint8_t  clip_to_restricted_range;
+} AV1RawFrameHeader;
+
+typedef struct AV1RawTileData {
+    uint8_t     *data;
+    size_t       data_size;
+    AVBufferRef *data_ref;
+} AV1RawTileData;
+
+typedef struct AV1RawTileGroup {
+    uint8_t  tile_start_and_end_present_flag;
+    uint16_t tg_start;
+    uint16_t tg_end;
+
+    AV1RawTileData tile_data;
+} AV1RawTileGroup;
+
+typedef struct AV1RawFrame {
+    AV1RawFrameHeader header;
+    AV1RawTileGroup   tile_group;
+} AV1RawFrame;
+
+typedef struct AV1RawTileList {
+    uint8_t output_frame_width_in_tiles_minus_1;
+    uint8_t output_frame_height_in_tiles_minus_1;
+    uint16_t tile_count_minus_1;
+
+    AV1RawTileData tile_data;
+} AV1RawTileList;
+
+typedef struct AV1RawMetadataHDRCLL {
+    uint16_t max_cll;
+    uint16_t max_fall;
+} AV1RawMetadataHDRCLL;
+
+typedef struct AV1RawMetadataHDRMDCV {
+    uint16_t primary_chromaticity_x[3];
+    uint16_t primary_chromaticity_y[3];
+    uint16_t white_point_chromaticity_x;
+    uint16_t white_point_chromaticity_y;
+    uint32_t luminance_max;
+    uint32_t luminance_min;
+} AV1RawMetadataHDRMDCV;
+
+typedef struct AV1RawMetadataScalability {
+    uint8_t scalability_mode_idc;
+    // TODO: more stuff.
+} AV1RawMetadataScalability;
+
+typedef struct AV1RawMetadataITUTT35 {
+    uint8_t itu_t_t35_country_code;
+    uint8_t itu_t_t35_country_code_extension_byte;
+
+    uint8_t     *payload;
+    size_t       payload_size;
+    AVBufferRef *payload_ref;
+} AV1RawMetadataITUTT35;
+
+typedef struct AV1RawMetadataTimecode {
+    uint8_t  counting_type;
+    uint8_t  full_timestamp_flag;
+    uint8_t  discontinuity_flag;
+    uint8_t  cnt_dropped_flag;
+    uint16_t n_frames;
+    uint8_t  seconds_value;
+    uint8_t  minutes_value;
+    uint8_t  hours_value;
+    uint8_t  seconds_flag;
+    uint8_t  minutes_flag;
+    uint8_t  hours_flag;
+    uint8_t  time_offset_length;
+    uint32_t time_offset_value;
+} AV1RawMetadataTimecode;
+
+typedef struct AV1RawMetadata {
+    uint64_t metadata_type;
+    union {
+        AV1RawMetadataHDRCLL      hdr_cll;
+        AV1RawMetadataHDRMDCV     hdr_mdcv;
+        AV1RawMetadataScalability scalability;
+        AV1RawMetadataITUTT35     itut_t35;
+        AV1RawMetadataTimecode    timecode;
+    } metadata;
+} AV1RawMetadata;
+
+
+typedef struct AV1RawOBU {
+    AV1RawOBUHeader header;
+
+    size_t obu_size;
+
+    union {
+        AV1RawSequenceHeader sequence_header;
+        AV1RawFrameHeader    frame_header;
+        AV1RawFrame          frame;
+        AV1RawTileGroup      tile_group;
+        AV1RawTileList       tile_list;
+        AV1RawMetadata       metadata;
+    } obu;
+} AV1RawOBU;
+
+typedef struct AV1ReferenceFrameState {
+    int valid;          // RefValid
+    int frame_id;       // RefFrameId
+    int upscaled_width; // RefUpscaledWidth
+    int frame_width;    // RefFrameWidth
+    int frame_height;   // RefFrameHeight
+    int render_width;   // RefRenderWidth
+    int render_height;  // RefRenderHeight
+    int frame_type;     // RefFrameType
+    int subsampling_x;  // RefSubsamplingX
+    int subsampling_y;  // RefSubsamplingY
+    int bit_depth;      // RefBitDepth
+    int order_hint;     // RefOrderHint
+} AV1ReferenceFrameState;
+
+typedef struct CodedBitstreamAV1Context {
+    AV1RawSequenceHeader *sequence_header;
+    AVBufferRef          *sequence_header_ref;
+
+    int seen_frame_header;
+
+    int temporal_id;
+    int spatial_id;
+    int operating_point_idc;
+
+    int bit_depth;
+    int frame_width;
+    int frame_height;
+    int upscaled_width;
+    int render_width;
+    int render_height;
+
+    int num_planes;
+    int coded_lossless;
+    int all_lossless;
+    int tile_cols;
+    int tile_rows;
+
+    AV1ReferenceFrameState ref[AV1_NUM_REF_FRAMES];
+
+    // Write buffer.
+    uint8_t *write_buffer;
+    size_t   write_buffer_size;
+} CodedBitstreamAV1Context;
+
+
+#endif /* AVCODEC_CBS_AV1_H */
diff --git a/libavcodec/cbs_av1_syntax_template.c b/libavcodec/cbs_av1_syntax_template.c
new file mode 100644
index 0000000000..0cea252083
--- /dev/null
+++ b/libavcodec/cbs_av1_syntax_template.c
@@ -0,0 +1,1693 @@
+/*
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+static int FUNC(obu_header)(CodedBitstreamContext *ctx, RWContext *rw,
+                            AV1RawOBUHeader *current)
+{
+    int err;
+    av_unused int zero = 0;
+
+    HEADER("OBU header");
+
+    fc(1, obu_forbidden_bit, 0, 0);
+
+    fc(4, obu_type, 0, AV1_OBU_PADDING);
+    flag(obu_extension_flag);
+    flag(obu_has_size_field);
+
+    fc(1, obu_reserved_1bit, 0, 0);
+
+    if (current->obu_extension_flag) {
+        fb(3, temporal_id);
+        fb(2, spatial_id);
+        fc(3, extension_header_reserved_3bits, 0, 0);
+    }
+
+    return 0;
+}
+
+static int FUNC(trailing_bits)(CodedBitstreamContext *ctx, RWContext *rw, int nb_bits)
+{
+    int err;
+
+    av_assert0(nb_bits > 0);
+
+    fixed(1, trailing_one_bit, 1);
+    --nb_bits;
+
+    while (nb_bits > 0) {
+        fixed(1, trailing_zero_bit, 0);
+        --nb_bits;
+    }
+
+    return 0;
+}
+
+static int FUNC(byte_alignment)(CodedBitstreamContext *ctx, RWContext *rw)
+{
+    int err;
+
+    while (byte_alignment(rw) != 0)
+        fixed(1, zero_bit, 0);
+
+    return 0;
+}
+
+static int FUNC(color_config)(CodedBitstreamContext *ctx, RWContext *rw,
+                              AV1RawColorConfig *current, int seq_profile)
+{
+    CodedBitstreamAV1Context *priv = ctx->priv_data;
+    int err;
+
+    flag(high_bitdepth);
+
+    if (seq_profile == FF_PROFILE_AV1_PROFESSIONAL &&
+        current->high_bitdepth) {
+        flag(twelve_bit);
+        priv->bit_depth = current->twelve_bit ? 12 : 10;
+    } else {
+        priv->bit_depth = current->high_bitdepth ? 10 : 8;
+    }
+
+    if (seq_profile == FF_PROFILE_AV1_HIGH)
+        infer(mono_chrome, 0);
+    else
+        flag(mono_chrome);
+    priv->num_planes = current->mono_chrome ? 1 : 3;
+
+    flag(color_description_present_flag);
+    if (current->color_description_present_flag) {
+        fb(8, color_primaries);
+        fb(8, transfer_characteristics);
+        fb(8, matrix_coefficients);
+    } else {
+        infer(color_primaries,          AVCOL_PRI_UNSPECIFIED);
+        infer(transfer_characteristics, AVCOL_TRC_UNSPECIFIED);
+        infer(matrix_coefficients,      AVCOL_SPC_UNSPECIFIED);
+    }
+
+    if (current->mono_chrome) {
+        infer(color_range,   1);
+        infer(subsampling_x, 1);
+        infer(subsampling_y, 1);
+        infer(chroma_sample_position, AV1_CSP_UNKNOWN);
+        infer(separate_uv_delta_q, 0);
+
+    } else if (current->color_primaries          == AVCOL_PRI_BT709 &&
+               current->transfer_characteristics == AVCOL_TRC_IEC61966_2_1 &&
+               current->matrix_coefficients      == AVCOL_SPC_RGB) {
+        infer(color_range,   1);
+        infer(subsampling_x, 0);
+        infer(subsampling_y, 0);
+        flag(separate_uv_delta_q);
+
+    } else {
+        flag(color_range);
+
+        if (seq_profile == FF_PROFILE_AV1_MAIN) {
+            infer(subsampling_x, 1);
+            infer(subsampling_y, 1);
+        } else if (seq_profile == FF_PROFILE_AV1_HIGH) {
+            infer(subsampling_x, 0);
+            infer(subsampling_y, 0);
+        } else {
+            if (priv->bit_depth == 12) {
+                fb(1, subsampling_x);
+                if (current->subsampling_x)
+                    fb(1, subsampling_y);
+                else
+                    infer(subsampling_y, 0);
+            } else {
+                infer(subsampling_x, 1);
+                infer(subsampling_y, 0);
+            }
+        }
+        if (current->subsampling_x && current->subsampling_y) {
+            fc(2, chroma_sample_position, AV1_CSP_UNKNOWN,
+                                          AV1_CSP_COLOCATED);
+        }
+
+        flag(separate_uv_delta_q);
+    }
+
+    return 0;
+}
+
+static int FUNC(timing_info)(CodedBitstreamContext *ctx, RWContext *rw,
+                             AV1RawTimingInfo *current)
+{
+    int err;
+
+    fc(32, num_units_in_display_tick, 1, MAX_UINT_BITS(32));
+    fc(32, time_scale,                1, MAX_UINT_BITS(32));
+
+    flag(equal_picture_interval);
+    if (current->equal_picture_interval)
+        uvlc(num_ticks_per_picture_minus_1, 0, MAX_UINT_BITS(32) - 1);
+
+    return 0;
+}
+
+static int FUNC(decoder_model_info)(CodedBitstreamContext *ctx, RWContext *rw,
+                                    AV1RawDecoderModelInfo *current)
+{
+    int err;
+
+    fb(5, buffer_delay_length_minus_1);
+    fb(32, num_units_in_decoding_tick);
+    fb(5,  buffer_removal_time_length_minus_1);
+    fb(5,  frame_presentation_time_length_minus_1);
+
+    return 0;
+}
+
+static int FUNC(sequence_header_obu)(CodedBitstreamContext *ctx, RWContext *rw,
+                                     AV1RawSequenceHeader *current)
+{
+    int i, err;
+
+    HEADER("Sequence Header");
+
+    fc(3, seq_profile, FF_PROFILE_AV1_MAIN,
+                       FF_PROFILE_AV1_PROFESSIONAL);
+    flag(still_picture);
+    flag(reduced_still_picture_header);
+
+    if (current->reduced_still_picture_header) {
+        infer(timing_info_present_flag,           0);
+        infer(decoder_model_info_present_flag,    0);
+        infer(initial_display_delay_present_flag, 0);
+        infer(operating_points_cnt_minus_1,       0);
+        infer(operating_point_idc[0],             0);
+
+        fb(5, seq_level_idx[0]);
+
+        infer(seq_tier[0], 0);
+        infer(decoder_model_present_for_this_op[0],         0);
+        infer(initial_display_delay_present_for_this_op[0], 0);
+
+    } else {
+        flag(timing_info_present_flag);
+        if (current->timing_info_present_flag) {
+            CHECK(FUNC(timing_info)(ctx, rw, &current->timing_info));
+
+            flag(decoder_model_info_present_flag);
+            if (current->decoder_model_info_present_flag) {
+                CHECK(FUNC(decoder_model_info)
+                          (ctx, rw, &current->decoder_model_info));
+            }
+        } else {
+            infer(decoder_model_info_present_flag, 0);
+        }
+
+        flag(initial_display_delay_present_flag);
+
+        fb(5, operating_points_cnt_minus_1);
+        for (i = 0; i <= current->operating_points_cnt_minus_1; i++) {
+            fbs(12, operating_point_idc[i], 1, i);
+            fbs(5,  seq_level_idx[i], 1, i);
+
+            if (current->seq_level_idx[i] > 7)
+                flags(seq_tier[i], 1, i);
+            else
+                infer(seq_tier[i], 0);
+
+            if (current->decoder_model_info_present_flag) {
+                flags(decoder_model_present_for_this_op[i], 1, i);
+                if (current->decoder_model_present_for_this_op[i]) {
+                    int n = current->decoder_model_info.buffer_delay_length_minus_1 + 1;
+                    fbs(n, decoder_buffer_delay[i], 1, i);
+                    fbs(n, encoder_buffer_delay[i], 1, i);
+                    flags(low_delay_mode_flag[i], 1, i);
+                }
+            } else {
+                infer(decoder_model_present_for_this_op[i], 0);
+            }
+
+            if (current->initial_display_delay_present_flag) {
+                flags(initial_display_delay_present_for_this_op[i], 1, i);
+                if (current->initial_display_delay_present_for_this_op[i])
+                    fbs(4, initial_display_delay_minus_1[i], 1, i);
+            }
+        }
+    }
+
+    fb(4, frame_width_bits_minus_1);
+    fb(4, frame_height_bits_minus_1);
+
+    fb(current->frame_width_bits_minus_1  + 1, max_frame_width_minus_1);
+    fb(current->frame_height_bits_minus_1 + 1, max_frame_height_minus_1);
+
+    if (current->reduced_still_picture_header)
+        infer(frame_id_numbers_present_flag, 0);
+    else
+        flag(frame_id_numbers_present_flag);
+    if (current->frame_id_numbers_present_flag) {
+        fb(4, delta_frame_id_length_minus_2);
+        fb(3, additional_frame_id_length_minus_1);
+    }
+
+    flag(use_128x128_superblock);
+    flag(enable_filter_intra);
+    flag(enable_intra_edge_filter);
+
+    if (current->reduced_still_picture_header) {
+        infer(enable_intraintra_compound, 0);
+        infer(enable_masked_compound,     0);
+        infer(enable_warped_motion,       0);
+        infer(enable_dual_filter,         0);
+        infer(enable_order_hint,          0);
+        infer(enable_jnt_comp,            0);
+        infer(enable_ref_frame_mvs,       0);
+
+        infer(seq_force_screen_content_tools,
+              AV1_SELECT_SCREEN_CONTENT_TOOLS);
+        infer(seq_force_integer_mv,
+              AV1_SELECT_INTEGER_MV);
+    } else {
+        flag(enable_intraintra_compound);
+        flag(enable_masked_compound);
+        flag(enable_warped_motion);
+        flag(enable_dual_filter);
+
+        flag(enable_order_hint);
+        if (current->enable_order_hint) {
+            flag(enable_jnt_comp);
+            flag(enable_ref_frame_mvs);
+        } else {
+            infer(enable_jnt_comp,      0);
+            infer(enable_ref_frame_mvs, 0);
+        }
+
+        flag(seq_choose_screen_content_tools);
+        if (current->seq_choose_screen_content_tools)
+            infer(seq_force_screen_content_tools,
+                  AV1_SELECT_SCREEN_CONTENT_TOOLS);
+        else
+            fb(1, seq_force_screen_content_tools);
+        if (current->seq_force_screen_content_tools > 0) {
+            flag(seq_choose_integer_mv);
+            if (current->seq_choose_integer_mv)
+                infer(seq_force_integer_mv,
+                      AV1_SELECT_INTEGER_MV);
+            else
+                fb(1, seq_force_integer_mv);
+        } else {
+            infer(seq_force_integer_mv, AV1_SELECT_INTEGER_MV);
+        }
+
+        if (current->enable_order_hint)
+            fb(3, order_hint_bits_minus_1);
+    }
+
+    flag(enable_superres);
+    flag(enable_cdef);
+    flag(enable_restoration);
+
+    CHECK(FUNC(color_config)(ctx, rw, &current->color_config,
+                             current->seq_profile));
+
+    flag(film_grain_params_present);
+
+    return 0;
+}
+
+static int FUNC(temporal_delimiter_obu)(CodedBitstreamContext *ctx, RWContext *rw)
+{
+    CodedBitstreamAV1Context *priv = ctx->priv_data;
+
+    HEADER("Temporal Delimiter");
+
+    priv->seen_frame_header = 0;
+
+    return 0;
+}
+
+static int FUNC(superres_params)(CodedBitstreamContext *ctx, RWContext *rw,
+                                 AV1RawFrameHeader *current)
+{
+    CodedBitstreamAV1Context  *priv = ctx->priv_data;
+    const AV1RawSequenceHeader *seq = priv->sequence_header;
+    int denom, err;
+
+    if (seq->enable_superres)
+        flag(use_superres);
+    else
+        infer(use_superres, 0);
+
+    if (current->use_superres) {
+        fb(3, coded_denom);
+        denom = current->coded_denom + AV1_SUPERRES_DENOM_MIN;
+    } else {
+        denom = AV1_SUPERRES_NUM;
+    }
+
+    priv->upscaled_width = priv->frame_width;
+    priv->frame_width = (priv->upscaled_width * AV1_SUPERRES_NUM +
+                         denom / 2) / denom;
+
+    return 0;
+}
+
+static int FUNC(frame_size)(CodedBitstreamContext *ctx, RWContext *rw,
+                            AV1RawFrameHeader *current)
+{
+    CodedBitstreamAV1Context  *priv = ctx->priv_data;
+    const AV1RawSequenceHeader *seq = priv->sequence_header;
+    int err;
+
+    if (current->frame_size_override_flag) {
+        fb(seq->frame_width_bits_minus_1 + 1,  frame_width_minus_1);
+        fb(seq->frame_height_bits_minus_1 + 1, frame_height_minus_1);
+
+        priv->frame_width  = current->frame_width_minus_1  + 1;
+        priv->frame_height = current->frame_height_minus_1 + 1;
+    } else {
+        priv->frame_width  = seq->max_frame_width_minus_1  + 1;
+        priv->frame_height = seq->max_frame_height_minus_1 + 1;
+    }
+
+    CHECK(FUNC(superres_params)(ctx, rw, current));
+
+    return 0;
+}
+
+static int FUNC(render_size)(CodedBitstreamContext *ctx, RWContext *rw,
+                             AV1RawFrameHeader *current)
+{
+    CodedBitstreamAV1Context *priv = ctx->priv_data;
+    int err;
+
+    flag(render_and_frame_size_different);
+
+    if (current->render_and_frame_size_different) {
+        fb(16, render_width_minus_1);
+        fb(16, render_height_minus_1);
+
+        priv->render_width  = current->render_width_minus_1  + 1;
+        priv->render_height = current->render_height_minus_1 + 1;
+    } else {
+        priv->render_width  = priv->upscaled_width;
+        priv->render_height = priv->frame_height;
+    }
+
+    return 0;
+}
+
+static int FUNC(frame_size_with_refs)(CodedBitstreamContext *ctx, RWContext *rw,
+                                      AV1RawFrameHeader *current)
+{
+    CodedBitstreamAV1Context *priv = ctx->priv_data;
+    int i, err;
+
+    for (i = 0; i < AV1_REFS_PER_FRAME; i++) {
+        flag(found_ref);
+        if (current->found_ref) {
+            AV1ReferenceFrameState *ref =
+                &priv->ref[current->ref_frame_idx[i]];
+
+            if (!ref->valid) {
+                av_log(ctx->log_ctx, AV_LOG_ERROR,
+                       "Missing reference frame needed for frame size "
+                       "(ref = %d, ref_frame_idx = %d).\n",
+                       i, current->ref_frame_idx[i]);
+                return AVERROR_INVALIDDATA;
+            }
+
+            priv->upscaled_width = ref->upscaled_width;
+            priv->frame_width    = ref->frame_width;
+            priv->frame_height   = ref->frame_height;
+            priv->render_width   = ref->render_width;
+            priv->render_height  = ref->render_height;
+            break;
+        }
+    }
+
+    if (current->found_ref == 0) {
+        CHECK(FUNC(frame_size)(ctx, rw, current));
+        CHECK(FUNC(render_size)(ctx, rw, current));
+    } else {
+        CHECK(FUNC(superres_params)(ctx, rw, current));
+    }
+
+    return 0;
+}
+
+static int FUNC(interpolation_filter)(CodedBitstreamContext *ctx, RWContext *rw,
+                                      AV1RawFrameHeader *current)
+{
+    int err;
+
+    flag(is_filter_switchable);
+    if (current->is_filter_switchable)
+        infer(interpolation_filter,
+              AV1_INTERPOLATION_FILTER_SWITCHABLE);
+    else
+        fb(2, interpolation_filter);
+
+    return 0;
+}
+
+static int FUNC(tile_info)(CodedBitstreamContext *ctx, RWContext *rw,
+                           AV1RawFrameHeader *current)
+{
+    CodedBitstreamAV1Context  *priv = ctx->priv_data;
+    const AV1RawSequenceHeader *seq = priv->sequence_header;
+    int mi_cols, mi_rows, sb_cols, sb_rows, sb_shift, sb_size;
+    int max_tile_width_sb, max_tile_height_sb, max_tile_area_sb;
+    int min_log2_tile_cols, max_log2_tile_cols, max_log2_tile_rows;
+    int min_log2_tiles, min_log2_tile_rows;
+    int i, err;
+
+    mi_cols = 2 * ((priv->frame_width  + 7) >> 3);
+    mi_rows = 2 * ((priv->frame_height + 7) >> 3);
+
+    sb_cols = seq->use_128x128_superblock ? ((mi_cols + 31) >> 5)
+                                          : ((mi_cols + 15) >> 4);
+    sb_rows = seq->use_128x128_superblock ? ((mi_rows + 31) >> 5)
+                                          : ((mi_rows + 15) >> 4);
+
+    sb_shift = seq->use_128x128_superblock ? 5 : 4;
+    sb_size  = sb_shift + 2;
+
+    max_tile_width_sb = AV1_MAX_TILE_WIDTH >> sb_size;
+    max_tile_area_sb  = AV1_MAX_TILE_AREA  >> (2 * sb_size);
+
+    min_log2_tile_cols = cbs_av1_tile_log2(max_tile_width_sb, sb_cols);
+    max_log2_tile_cols = cbs_av1_tile_log2(1, FFMIN(sb_cols, AV1_MAX_TILE_COLS));
+    max_log2_tile_rows = cbs_av1_tile_log2(1, FFMIN(sb_rows, AV1_MAX_TILE_ROWS));
+    min_log2_tiles = FFMAX(min_log2_tile_cols,
+                           cbs_av1_tile_log2(max_tile_area_sb, sb_rows * sb_cols));
+
+    flag(uniform_tile_spacing_flag);
+
+    if (current->uniform_tile_spacing_flag) {
+        int tile_width_sb, tile_height_sb;
+
+        increment(tile_cols_log2, min_log2_tile_cols, max_log2_tile_cols);
+
+        tile_width_sb = (sb_cols + (1 << current->tile_cols_log2) - 1) >>
+            current->tile_cols_log2;
+        current->tile_cols = (sb_cols + tile_width_sb - 1) / tile_width_sb;
+
+        min_log2_tile_rows = FFMAX(min_log2_tiles - current->tile_cols_log2, 0);
+
+        increment(tile_rows_log2, min_log2_tile_rows, max_log2_tile_rows);
+
+        tile_height_sb = (sb_rows + (1 << current->tile_rows_log2) - 1) >>
+            current->tile_rows_log2;
+        current->tile_rows = (sb_rows + tile_height_sb - 1) / tile_height_sb;
+
+    } else {
+        int widest_tile_sb, start_sb, size_sb, max_width, max_height;
+
+        widest_tile_sb = 0;
+
+        start_sb = 0;
+        for (i = 0; start_sb < sb_cols && i < AV1_MAX_TILE_COLS; i++) {
+            max_width = FFMIN(sb_cols - start_sb, max_tile_width_sb);
+            ns(max_width, width_in_sbs_minus_1[i], 1, i);
+            size_sb = current->width_in_sbs_minus_1[i] + 1;
+            widest_tile_sb = FFMAX(size_sb, widest_tile_sb);
+            start_sb += size_sb;
+        }
+        current->tile_cols_log2 = cbs_av1_tile_log2(1, i);
+        current->tile_cols = i;
+
+        if (min_log2_tiles > 0)
+            max_tile_area_sb = (sb_rows * sb_cols) >> (min_log2_tiles + 1);
+        else
+            max_tile_area_sb = sb_rows * sb_cols;
+        max_tile_height_sb = FFMAX(max_tile_area_sb / widest_tile_sb, 1);
+
+        start_sb = 0;
+        for (i = 0; start_sb < sb_rows && i < AV1_MAX_TILE_ROWS; i++) {
+            max_height = FFMIN(sb_rows - start_sb, max_tile_height_sb);
+            ns(max_height, height_in_sbs_minus_1[i], 1, i);
+            size_sb = current->height_in_sbs_minus_1[i] + 1;
+            start_sb += size_sb;
+        }
+        current->tile_rows_log2 = cbs_av1_tile_log2(1, i);
+        current->tile_rows = i;
+    }
+
+    if (current->tile_cols_log2 > 0 ||
+        current->tile_rows_log2 > 0) {
+        fb(current->tile_cols_log2 + current->tile_rows_log2,
+           context_update_tile_id);
+        fb(2, tile_size_bytes_minus1);
+    } else {
+        infer(context_update_tile_id, 0);
+    }
+
+    priv->tile_cols = current->tile_cols;
+    priv->tile_rows = current->tile_rows;
+
+    return 0;
+}
+
+static int FUNC(quantization_params)(CodedBitstreamContext *ctx, RWContext *rw,
+                                     AV1RawFrameHeader *current)
+{
+    CodedBitstreamAV1Context  *priv = ctx->priv_data;
+    const AV1RawSequenceHeader *seq = priv->sequence_header;
+    int err;
+
+    fb(8, base_q_idx);
+
+    delta_q(delta_q_y_dc);
+
+    if (priv->num_planes > 1) {
+        if (seq->color_config.separate_uv_delta_q)
+            flag(diff_uv_delta);
+        else
+            infer(diff_uv_delta, 0);
+
+        delta_q(delta_q_u_dc);
+        delta_q(delta_q_u_ac);
+
+        if (current->diff_uv_delta) {
+            delta_q(delta_q_v_dc);
+            delta_q(delta_q_v_ac);
+        } else {
+            infer(delta_q_v_dc, current->delta_q_u_dc);
+            infer(delta_q_v_ac, current->delta_q_u_ac);
+        }
+    } else {
+        infer(delta_q_u_dc, 0);
+        infer(delta_q_u_ac, 0);
+        infer(delta_q_v_dc, 0);
+        infer(delta_q_v_ac, 0);
+    }
+
+    flag(using_qmatrix);
+    if (current->using_qmatrix) {
+        fb(4, qm_y);
+        fb(4, qm_u);
+        if (seq->color_config.separate_uv_delta_q)
+            fb(4, qm_v);
+        else
+            infer(qm_v, current->qm_u);
+    }
+
+    return 0;
+}
+
+static int FUNC(segmentation_params)(CodedBitstreamContext *ctx, RWContext *rw,
+                                     AV1RawFrameHeader *current)
+{
+    static const uint8_t bits[AV1_SEG_LVL_MAX] = { 8, 6, 6, 6, 6, 3, 0, 0 };
+    static const uint8_t sign[AV1_SEG_LVL_MAX] = { 1, 1, 1, 1, 1, 0, 0, 0 };
+    int i, j, err;
+
+    flag(segmentation_enabled);
+
+    if (current->segmentation_enabled) {
+        if (current->primary_ref_frame == AV1_PRIMARY_REF_NONE) {
+            infer(segmentation_update_map,      1);
+            infer(segmentation_temporal_update, 0);
+            infer(segmentation_update_data,     1);
+        } else {
+            flag(segmentation_update_map);
+            if (current->segmentation_update_map)
+                flag(segmentation_temporal_update);
+            else
+                infer(segmentation_temporal_update, 0);
+            flag(segmentation_update_data);
+        }
+
+        if (current->segmentation_update_data) {
+            for (i = 0; i < AV1_MAX_SEGMENTS; i++) {
+                for (j = 0; j < AV1_SEG_LVL_MAX; j++) {
+                    flags(feature_enabled[i][j], 2, i, j);
+
+                    if (current->feature_enabled[i][j] && bits[j] > 0) {
+                        if (sign[j])
+                            sus(1 + bits[j], feature_value[i][j], 2, i, j);
+                        else
+                            fbs(bits[j], feature_value[i][j], 2, i, j);
+                    } else {
+                        infer(feature_value[i][j], 0);
+                    }
+                }
+            }
+        }
+    } else {
+        for (i = 0; i < AV1_MAX_SEGMENTS; i++) {
+            for (j = 0; j < AV1_SEG_LVL_MAX; j++) {
+                infer(feature_enabled[i][j], 0);
+                infer(feature_value[i][j],   0);
+            }
+        }
+    }
+
+    return 0;
+}
+
+static int FUNC(delta_q_params)(CodedBitstreamContext *ctx, RWContext *rw,
+                                AV1RawFrameHeader *current)
+{
+    int err;
+
+    if (current->base_q_idx > 0)
+        flag(delta_q_present);
+    else
+        infer(delta_q_present, 0);
+
+    if (current->delta_q_present)
+        fb(2, delta_q_res);
+
+    return 0;
+}
+
+static int FUNC(delta_lf_params)(CodedBitstreamContext *ctx, RWContext *rw,
+                                 AV1RawFrameHeader *current)
+{
+    int err;
+
+    if (current->delta_q_present) {
+        if (!current->allow_intrabc)
+            flag(delta_lf_present);
+        else
+            infer(delta_lf_present, 0);
+        if (current->delta_lf_present) {
+            fb(2, delta_lf_res);
+            flag(delta_lf_multi);
+        } else {
+            infer(delta_lf_res,   0);
+            infer(delta_lf_multi, 0);
+        }
+    } else {
+        infer(delta_lf_present, 0);
+        infer(delta_lf_res,     0);
+        infer(delta_lf_multi,   0);
+    }
+
+    return 0;
+}
+
+static int FUNC(loop_filter_params)(CodedBitstreamContext *ctx, RWContext *rw,
+                                    AV1RawFrameHeader *current)
+{
+    CodedBitstreamAV1Context *priv = ctx->priv_data;
+    int i, err;
+
+    if (priv->coded_lossless || current->allow_intrabc) {
+        infer(loop_filter_level[0], 0);
+        infer(loop_filter_level[1], 0);
+        infer(loop_filter_ref_deltas[AV1_REF_FRAME_INTRA],    1);
+        infer(loop_filter_ref_deltas[AV1_REF_FRAME_LAST],     0);
+        infer(loop_filter_ref_deltas[AV1_REF_FRAME_LAST2],    0);
+        infer(loop_filter_ref_deltas[AV1_REF_FRAME_LAST3],    0);
+        infer(loop_filter_ref_deltas[AV1_REF_FRAME_BWDREF],   0);
+        infer(loop_filter_ref_deltas[AV1_REF_FRAME_GOLDEN],  -1);
+        infer(loop_filter_ref_deltas[AV1_REF_FRAME_ALTREF],  -1);
+        infer(loop_filter_ref_deltas[AV1_REF_FRAME_ALTREF2], -1);
+        for (i = 0; i < 2; i++)
+            infer(loop_filter_mode_deltas[i], 0);
+        return 0;
+    }
+
+    fb(6, loop_filter_level[0]);
+    fb(6, loop_filter_level[1]);
+
+    if (priv->num_planes > 1) {
+        if (current->loop_filter_level[0] ||
+            current->loop_filter_level[1]) {
+            fb(6, loop_filter_level[2]);
+            fb(6, loop_filter_level[3]);
+        }
+    }
+
+    fb(3, loop_filter_sharpness);
+
+    flag(loop_filter_delta_enabled);
+    if (current->loop_filter_delta_enabled) {
+        flag(loop_filter_delta_update);
+        if (current->loop_filter_delta_update) {
+            for (i = 0; i < AV1_TOTAL_REFS_PER_FRAME; i++) {
+                flags(update_ref_delta[i], 1, i);
+                if (current->update_ref_delta[i])
+                    sus(1 + 6, loop_filter_ref_deltas[i], 1, i);
+            }
+            for (i = 0; i < 2; i++) {
+                flags(update_mode_delta[i], 1, i);
+                if (current->update_mode_delta[i])
+                    sus(1 + 6, loop_filter_mode_deltas[i], 1, i);
+            }
+        }
+    }
+
+    return 0;
+}
+
+static int FUNC(cdef_params)(CodedBitstreamContext *ctx, RWContext *rw,
+                             AV1RawFrameHeader *current)
+{
+    CodedBitstreamAV1Context  *priv = ctx->priv_data;
+    const AV1RawSequenceHeader *seq = priv->sequence_header;
+    int i, err;
+
+    if (priv->coded_lossless || current->allow_intrabc ||
+        !seq->enable_cdef) {
+        infer(cdef_damping_minus_3, 0);
+        infer(cdef_bits, 0);
+        infer(cdef_y_pri_strength[0],  0);
+        infer(cdef_y_sec_strength[0],  0);
+        infer(cdef_uv_pri_strength[0], 0);
+        infer(cdef_uv_sec_strength[0], 0);
+
+        return 0;
+    }
+
+    fb(2, cdef_damping_minus_3);
+    fb(2, cdef_bits);
+
+    for (i = 0; i < (1 << current->cdef_bits); i++) {
+        fbs(4, cdef_y_pri_strength[i], 1, i);
+        fbs(2, cdef_y_sec_strength[i], 1, i);
+
+        if (priv->num_planes > 1) {
+            fbs(4, cdef_uv_pri_strength[i], 1, i);
+            fbs(2, cdef_uv_sec_strength[i], 1, i);
+        }
+    }
+
+    return 0;
+}
+
+static int FUNC(lr_params)(CodedBitstreamContext *ctx, RWContext *rw,
+                           AV1RawFrameHeader *current)
+{
+    CodedBitstreamAV1Context  *priv = ctx->priv_data;
+    const AV1RawSequenceHeader *seq = priv->sequence_header;
+    int uses_lr,  uses_chroma_lr;
+    int i, err;
+
+    if (priv->all_lossless || current->allow_intrabc ||
+        !seq->enable_restoration) {
+        return 0;
+    }
+
+    uses_lr = uses_chroma_lr = 0;
+    for (i = 0; i < priv->num_planes; i++) {
+        fbs(2, lr_type[i], 1, i);
+
+        if (current->lr_type[i] != 0) {
+            uses_lr = 1;
+            if (i > 0)
+                uses_chroma_lr = 1;
+        }
+    }
+
+    if (uses_lr) {
+        if (seq->use_128x128_superblock)
+            increment(lr_unit_shift, 1, 2);
+        else
+            increment(lr_unit_shift, 0, 2);
+
+        if(seq->color_config.subsampling_x &&
+           seq->color_config.subsampling_y && uses_chroma_lr) {
+            fb(1, lr_uv_shift);
+        } else {
+            infer(lr_uv_shift, 0);
+        }
+    }
+
+    return 0;
+}
+
+static int FUNC(read_tx_mode)(CodedBitstreamContext *ctx, RWContext *rw,
+                              AV1RawFrameHeader *current)
+{
+    CodedBitstreamAV1Context *priv = ctx->priv_data;
+    int err;
+
+    if (priv->coded_lossless)
+        infer(tx_mode, 0);
+    else
+        increment(tx_mode, 1, 2);
+
+    return 0;
+}
+
+static int FUNC(frame_reference_mode)(CodedBitstreamContext *ctx, RWContext *rw,
+                                      AV1RawFrameHeader *current)
+{
+    int err;
+
+    if (current->frame_type == AV1_FRAME_INTRA_ONLY ||
+        current->frame_type == AV1_FRAME_KEY)
+        infer(reference_select, 0);
+    else
+        flag(reference_select);
+
+    return 0;
+}
+
+static int FUNC(skip_mode_params)(CodedBitstreamContext *ctx, RWContext *rw,
+                                  AV1RawFrameHeader *current)
+{
+    CodedBitstreamAV1Context  *priv = ctx->priv_data;
+    const AV1RawSequenceHeader *seq = priv->sequence_header;
+    int skip_mode_allowed;
+    int err;
+
+    if (current->frame_type == AV1_FRAME_KEY ||
+        current->frame_type == AV1_FRAME_INTRA_ONLY ||
+        !current->reference_select || !seq->enable_order_hint) {
+        skip_mode_allowed = 0;
+    } else {
+        int forward_idx,  backward_idx;
+        int forward_hint, backward_hint;
+        int ref_hint, dist, i;
+
+        forward_idx  = -1;
+        backward_idx = -1;
+        for (i = 0; i < AV1_REFS_PER_FRAME; i++) {
+            ref_hint = priv->ref[i].order_hint;
+            dist = cbs_av1_get_relative_dist(seq, ref_hint,
+                                             current->order_hint);
+            if (dist < 0) {
+                if (forward_idx < 0 ||
+                    cbs_av1_get_relative_dist(seq, ref_hint,
+                                              forward_hint) > 0) {
+                    forward_idx  = i;
+                    forward_hint = ref_hint;
+                }
+            } else if (dist > 0) {
+                if (backward_idx < 0 ||
+                    cbs_av1_get_relative_dist(seq, ref_hint,
+                                              backward_hint) < 0) {
+                    backward_idx  = i;
+                    backward_hint = ref_hint;
+                }
+            }
+        }
+
+        if (forward_idx < 0) {
+            skip_mode_allowed = 0;
+        } else if (backward_idx >= 0) {
+            skip_mode_allowed = 1;
+            // Frames for skip mode are forward_idx and backward_idx.
+        } else {
+            int second_forward_idx;
+            int second_forward_hint;
+
+            second_forward_idx = -1;
+            for (i = 0; i < AV1_REFS_PER_FRAME; i++) {
+                ref_hint = priv->ref[i].order_hint;
+                if (cbs_av1_get_relative_dist(seq, ref_hint,
+                                              forward_hint) < 0) {
+                    if (second_forward_idx < 0 ||
+                        cbs_av1_get_relative_dist(seq, ref_hint,
+                                                  second_forward_hint) > 0) {
+                        second_forward_idx  = i;
+                        second_forward_hint = ref_hint;
+                    }
+                }
+            }
+
+            if (second_forward_idx < 0) {
+                skip_mode_allowed = 0;
+            } else {
+                skip_mode_allowed = 1;
+                // Frames for skip mode are forward_idx and second_forward_idx.
+            }
+        }
+    }
+
+    if (skip_mode_allowed)
+        flag(skip_mode_present);
+    else
+        infer(skip_mode_present, 0);
+
+    return 0;
+}
+
+static int FUNC(global_motion_param)(CodedBitstreamContext *ctx, RWContext *rw,
+                                     AV1RawFrameHeader *current,
+                                     int type, int ref, int idx)
+{
+    uint32_t abs_bits, prec_bits, num_syms;
+    int err;
+
+    if (idx < 2) {
+        if (type == AV1_WARP_MODEL_TRANSLATION) {
+            abs_bits  = AV1_GM_ABS_TRANS_ONLY_BITS  - !current->allow_high_precision_mv;
+            prec_bits = AV1_GM_TRANS_ONLY_PREC_BITS - !current->allow_high_precision_mv;
+        } else {
+            abs_bits  = AV1_GM_ABS_TRANS_BITS;
+            prec_bits = AV1_GM_TRANS_PREC_BITS;
+        }
+    } else {
+        abs_bits  = AV1_GM_ABS_ALPHA_BITS;
+        prec_bits = AV1_GM_ALPHA_PREC_BITS;
+    }
+
+    num_syms = 2 * (1 << abs_bits) + 1;
+    subexp(gm_params[ref][idx], num_syms, 2, ref, idx);
+
+    // Actual gm_params value is not reconstructed here.
+    (void)prec_bits;
+
+    return 0;
+}
+
+static int FUNC(global_motion_params)(CodedBitstreamContext *ctx, RWContext *rw,
+                                      AV1RawFrameHeader *current)
+{
+    int ref, type;
+    int err;
+
+    if (current->frame_type == AV1_FRAME_KEY ||
+        current->frame_type == AV1_FRAME_INTRA_ONLY)
+        return 0;
+
+    for (ref = AV1_REF_FRAME_LAST; ref <= AV1_REF_FRAME_ALTREF; ref++) {
+        flags(is_global[ref], 1, ref);
+        if (current->is_global[ref]) {
+            flags(is_rot_zoom[ref], 1, ref);
+            if (current->is_rot_zoom[ref]) {
+                type = AV1_WARP_MODEL_ROTZOOM;
+            } else {
+                flags(is_translation[ref], 1, ref);
+                type = current->is_translation[ref] ? AV1_WARP_MODEL_TRANSLATION
+                                                    : AV1_WARP_MODEL_AFFINE;
+            }
+        } else {
+            type = AV1_WARP_MODEL_IDENTITY;
+        }
+
+        if (type >= AV1_WARP_MODEL_ROTZOOM) {
+            CHECK(FUNC(global_motion_param)(ctx, rw, current, type, ref, 2));
+            CHECK(FUNC(global_motion_param)(ctx, rw, current, type, ref, 3));
+            if (type == AV1_WARP_MODEL_AFFINE) {
+                CHECK(FUNC(global_motion_param)(ctx, rw, current, type, ref, 4));
+                CHECK(FUNC(global_motion_param)(ctx, rw, current, type, ref, 5));
+            } else {
+                // gm_params[ref][4] = -gm_params[ref][3]
+                // gm_params[ref][5] =  gm_params[ref][2]
+            }
+        }
+        if (type >= AV1_WARP_MODEL_TRANSLATION) {
+            CHECK(FUNC(global_motion_param)(ctx, rw, current, type, ref, 0));
+            CHECK(FUNC(global_motion_param)(ctx, rw, current, type, ref, 1));
+        }
+    }
+
+    return 0;
+}
+
+static int FUNC(film_grain_params)(CodedBitstreamContext *ctx, RWContext *rw,
+                                   AV1RawFrameHeader *current)
+{
+    CodedBitstreamAV1Context  *priv = ctx->priv_data;
+    const AV1RawSequenceHeader *seq = priv->sequence_header;
+    int num_pos_luma, num_pos_chroma;
+    int i, err;
+
+    if (!seq->film_grain_params_present ||
+        (!current->show_frame && !current->showable_frame))
+        return 0;
+
+    flag(apply_grain);
+
+    if (!current->apply_grain)
+        return 0;
+
+    fb(16, grain_seed);
+
+    if (current->frame_type == AV1_FRAME_INTER)
+        flag(update_grain);
+    else
+        infer(update_grain, 1);
+
+    if (!current->update_grain) {
+        fb(3, film_grain_params_ref_idx);
+        return 0;
+    }
+
+    fb(4, num_y_points);
+    for (i = 0; i < current->num_y_points; i++) {
+        fbs(8, point_y_value[i],   1, i);
+        fbs(8, point_y_scaling[i], 1, i);
+    }
+
+    if (seq->color_config.mono_chrome)
+        infer(chroma_scaling_from_luma, 0);
+    else
+        flag(chroma_scaling_from_luma);
+
+    if (seq->color_config.mono_chrome ||
+        current->chroma_scaling_from_luma ||
+        (seq->color_config.subsampling_x == 1 &&
+         seq->color_config.subsampling_y == 1 &&
+         current->num_y_points == 0)) {
+        infer(num_cb_points, 0);
+        infer(num_cr_points, 0);
+    } else {
+        fb(4, num_cb_points);
+        for (i = 0; i < current->num_cb_points; i++) {
+            fbs(8, point_cb_value[i],   1, i);
+            fbs(8, point_cb_scaling[i], 1, i);
+        }
+        fb(4, num_cr_points);
+        for (i = 0; i < current->num_cr_points; i++) {
+            fbs(8, point_cr_value[i],   1, i);
+            fbs(8, point_cr_scaling[i], 1, i);
+        }
+    }
+
+    fb(2, grain_scaling_minus_8);
+    fb(2, ar_coeff_lag);
+    num_pos_luma = 2 * current->ar_coeff_lag * (current->ar_coeff_lag + 1);
+    if (current->num_y_points) {
+        num_pos_chroma = num_pos_luma + 1;
+        for (i = 0; i < num_pos_luma; i++)
+            fbs(8, ar_coeffs_y_plus_128[i], 1, i);
+    } else {
+        num_pos_chroma = num_pos_luma;
+    }
+    if (current->chroma_scaling_from_luma || current->num_cb_points) {
+        for (i = 0; i < num_pos_chroma; i++)
+            fbs(8, ar_coeffs_cb_plus_128[i], 1, i);
+    }
+    if (current->chroma_scaling_from_luma || current->num_cr_points) {
+        for (i = 0; i < num_pos_chroma; i++)
+            fbs(8, ar_coeffs_cr_plus_128[i], 1, i);
+    }
+    fb(2, ar_coeff_shift_minus_6);
+    fb(2, grain_scale_shift);
+    if (current->num_cb_points) {
+        fb(8, cb_mult);
+        fb(8, cb_luma_mult);
+        fb(9, cb_offset);
+    }
+    if (current->num_cr_points) {
+        fb(8, cr_mult);
+        fb(8, cr_luma_mult);
+        fb(9, cr_offset);
+    }
+
+    flag(overlap_flag);
+    flag(clip_to_restricted_range);
+
+    return 0;
+}
+
+static int FUNC(uncompressed_header)(CodedBitstreamContext *ctx, RWContext *rw,
+                                     AV1RawFrameHeader *current)
+{
+    CodedBitstreamAV1Context *priv = ctx->priv_data;
+    const AV1RawSequenceHeader *seq;
+    int id_len, diff_len, all_frames, frame_is_intra, order_hint_bits;
+    int i, err;
+
+    if (!priv->sequence_header) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "No sequence header available: "
+               "unable to decode frame header.\n");
+        return AVERROR_INVALIDDATA;
+    }
+    seq = priv->sequence_header;
+
+    id_len = seq->additional_frame_id_length_minus_1 +
+             seq->delta_frame_id_length_minus_2 + 3;
+    all_frames = (1 << AV1_NUM_REF_FRAMES) - 1;
+
+    if (seq->reduced_still_picture_header) {
+        infer(show_existing_frame, 0);
+        infer(frame_type,     AV1_FRAME_KEY);
+        infer(show_frame,     1);
+        infer(showable_frame, 0);
+        frame_is_intra = 1;
+
+    } else {
+        flag(show_existing_frame);
+
+        if (current->show_existing_frame) {
+            AV1ReferenceFrameState *frame;
+
+            fb(3, frame_to_show_map_idx);
+            frame = &priv->ref[current->frame_to_show_map_idx];
+
+            if (seq->decoder_model_info_present_flag &&
+                !seq->timing_info.equal_picture_interval) {
+                fb(seq->decoder_model_info.frame_presentation_time_length_minus_1 + 1,
+                   frame_presentation_time);
+            }
+
+            if (seq->frame_id_numbers_present_flag)
+                fb(id_len, display_frame_id);
+
+            if (frame->frame_type == AV1_FRAME_KEY)
+                infer(refresh_frame_flags, all_frames);
+            else
+                infer(refresh_frame_flags, 0);
+
+            return 0;
+        }
+
+        fb(2, frame_type);
+        frame_is_intra = (current->frame_type == AV1_FRAME_INTRA_ONLY ||
+                          current->frame_type == AV1_FRAME_KEY);
+
+        flag(show_frame);
+        if (current->show_frame &&
+            seq->decoder_model_info_present_flag &&
+            !seq->timing_info.equal_picture_interval) {
+            fb(seq->decoder_model_info.frame_presentation_time_length_minus_1 + 1,
+               frame_presentation_time);
+        }
+        if (current->show_frame)
+            infer(showable_frame, current->frame_type != AV1_FRAME_KEY);
+        else
+            flag(showable_frame);
+
+        if (current->frame_type == AV1_FRAME_SWITCH ||
+            (current->frame_type == AV1_FRAME_KEY && current->show_frame))
+            infer(error_resilient_mode, 1);
+        else
+            flag(error_resilient_mode);
+    }
+
+    if (current->frame_type == AV1_FRAME_KEY && current->show_frame) {
+        for (i = 0; i < AV1_NUM_REF_FRAMES; i++) {
+            priv->ref[i].valid = 0;
+            priv->ref[i].order_hint = 0;
+        }
+    }
+
+    flag(disable_cdf_update);
+
+    if (seq->seq_force_screen_content_tools ==
+        AV1_SELECT_SCREEN_CONTENT_TOOLS) {
+        flag(allow_screen_content_tools);
+    } else {
+        infer(allow_screen_content_tools,
+              seq->seq_force_screen_content_tools);
+    }
+    if (current->allow_screen_content_tools) {
+        if (seq->seq_force_integer_mv == AV1_SELECT_INTEGER_MV)
+            flag(force_integer_mv);
+        else
+            infer(force_integer_mv, seq->seq_force_integer_mv);
+    } else {
+        infer(force_integer_mv, 0);
+    }
+
+    if (seq->frame_id_numbers_present_flag) {
+        fb(id_len, current_frame_id);
+
+        diff_len = seq->delta_frame_id_length_minus_2 + 2;
+        for (i = 0; i < AV1_NUM_REF_FRAMES; i++) {
+            if (current->current_frame_id > (1 << diff_len)) {
+                if (priv->ref[i].frame_id > current->current_frame_id ||
+                    priv->ref[i].frame_id < (current->current_frame_id -
+                                             (1 << diff_len)))
+                    priv->ref[i].valid = 0;
+            } else {
+                if (priv->ref[i].frame_id > current->current_frame_id &&
+                    priv->ref[i].frame_id < ((1 << id_len) +
+                                             current->current_frame_id -
+                                             (1 << diff_len)))
+                    priv->ref[i].valid = 0;
+            }
+        }
+    } else {
+        infer(current_frame_id, 0);
+    }
+
+    if (current->frame_type == AV1_FRAME_SWITCH)
+        infer(frame_size_override_flag, 1);
+    else if(seq->reduced_still_picture_header)
+        infer(frame_size_override_flag, 0);
+    else
+        flag(frame_size_override_flag);
+
+    order_hint_bits =
+        seq->enable_order_hint ? seq->order_hint_bits_minus_1 + 1 : 0;
+    if (order_hint_bits > 0)
+        fb(order_hint_bits, order_hint);
+    else
+        infer(order_hint, 0);
+
+    if (frame_is_intra || current->error_resilient_mode)
+        infer(primary_ref_frame, AV1_PRIMARY_REF_NONE);
+    else
+        fb(3, primary_ref_frame);
+
+    if (seq->decoder_model_info_present_flag) {
+        flag(buffer_removal_time_present_flag);
+        if (current->buffer_removal_time_present_flag) {
+            for (i = 0; i <= seq->operating_points_cnt_minus_1; i++) {
+                if (seq->decoder_model_present_for_this_op[i]) {
+                    int op_pt_idc = seq->operating_point_idc[i];
+                    int in_temporal_layer = (op_pt_idc >>  priv->temporal_id    ) & 1;
+                    int in_spatial_layer  = (op_pt_idc >> (priv->spatial_id + 8)) & 1;
+                    if (seq->operating_point_idc[i] == 0 ||
+                        in_temporal_layer || in_spatial_layer) {
+                        fbs(seq->decoder_model_info.buffer_removal_time_length_minus_1 + 1,
+                            buffer_removal_time[i], 1, i);
+                    }
+                }
+            }
+        }
+    }
+
+    if (current->frame_type == AV1_FRAME_SWITCH ||
+        (current->frame_type == AV1_FRAME_KEY && current->show_frame))
+        infer(refresh_frame_flags, all_frames);
+    else
+        fb(8, refresh_frame_flags);
+
+    if (!frame_is_intra || current->refresh_frame_flags != all_frames) {
+        if (current->error_resilient_mode && seq->enable_order_hint) {
+            for (i = 0; i < AV1_NUM_REF_FRAMES; i++) {
+                fbs(order_hint_bits, ref_order_hint[i], 1, i);
+                if (current->ref_order_hint[i] != priv->ref[i].order_hint)
+                    priv->ref[i].valid = 0;
+            }
+        }
+    }
+
+    if (current->frame_type == AV1_FRAME_KEY ||
+        current->frame_type == AV1_FRAME_INTRA_ONLY) {
+        CHECK(FUNC(frame_size)(ctx, rw, current));
+        CHECK(FUNC(render_size)(ctx, rw, current));
+
+        if (current->allow_screen_content_tools &&
+            priv->upscaled_width == priv->frame_width)
+            flag(allow_intrabc);
+        else
+            infer(allow_intrabc, 0);
+
+    } else {
+        if (!seq->enable_order_hint) {
+            infer(frame_refs_short_signaling, 0);
+        } else {
+            flag(frame_refs_short_signaling);
+            if (current->frame_refs_short_signaling) {
+                fb(3, last_frame_idx);
+                fb(3, golden_frame_idx);
+
+                for (i = 0; i < AV1_REFS_PER_FRAME; i++) {
+                    if (i == 0)
+                        infer(ref_frame_idx[i], current->last_frame_idx);
+                    else if (i == AV1_REF_FRAME_GOLDEN -
+                                  AV1_REF_FRAME_LAST)
+                        infer(ref_frame_idx[i], current->golden_frame_idx);
+                    else
+                        infer(ref_frame_idx[i], -1);
+                }
+            }
+        }
+
+        for (i = 0; i < AV1_REFS_PER_FRAME; i++) {
+            if (!current->frame_refs_short_signaling)
+                fbs(3, ref_frame_idx[i], 1, i);
+            if (seq->frame_id_numbers_present_flag) {
+                fb(seq->delta_frame_id_length_minus_2 + 2,
+                   delta_frame_id_minus1);
+            }
+        }
+
+        if (current->frame_size_override_flag &&
+            !current->error_resilient_mode) {
+            CHECK(FUNC(frame_size_with_refs)(ctx, rw, current));
+        } else {
+            CHECK(FUNC(frame_size)(ctx, rw, current));
+            CHECK(FUNC(render_size)(ctx, rw, current));
+        }
+
+        if (current->force_integer_mv)
+            infer(allow_high_precision_mv, 0);
+        else
+            flag(allow_high_precision_mv);
+
+        CHECK(FUNC(interpolation_filter)(ctx, rw, current));
+
+        flag(is_motion_mode_switchable);
+
+        if (current->error_resilient_mode ||
+            !seq->enable_ref_frame_mvs)
+            infer(use_ref_frame_mvs, 0);
+        else
+            flag(use_ref_frame_mvs);
+
+        infer(allow_intrabc, 0);
+    }
+
+    if (!frame_is_intra) {
+        // Derive reference frame sign biases.
+    }
+
+    if (seq->reduced_still_picture_header || current->disable_cdf_update)
+        infer(disable_frame_end_update_cdf, 1);
+    else
+        flag(disable_frame_end_update_cdf);
+
+    if (current->primary_ref_frame == AV1_PRIMARY_REF_NONE) {
+        // Init non-coeff CDFs.
+        // Setup past independence.
+    } else {
+        // Load CDF tables from previous frame.
+        // Load params from previous frame.
+    }
+
+    if (current->use_ref_frame_mvs) {
+        // Perform motion field estimation process.
+    }
+
+    CHECK(FUNC(tile_info)(ctx, rw, current));
+
+    CHECK(FUNC(quantization_params)(ctx, rw, current));
+
+    CHECK(FUNC(segmentation_params)(ctx, rw, current));
+
+    CHECK(FUNC(delta_q_params)(ctx, rw, current));
+
+    CHECK(FUNC(delta_lf_params)(ctx, rw, current));
+
+    // Init coeff CDFs / load previous segments.
+
+    priv->coded_lossless = 1;
+    for (i = 0; i < AV1_MAX_SEGMENTS; i++) {
+        int qindex;
+        if (current->feature_enabled[i][AV1_SEG_LVL_ALT_Q]) {
+            qindex = (current->base_q_idx +
+                      current->feature_value[i][AV1_SEG_LVL_ALT_Q]);
+        } else {
+            qindex = current->base_q_idx;
+        }
+        qindex = av_clip_uintp2(qindex, 8);
+
+        if (qindex                || current->delta_q_y_dc ||
+            current->delta_q_u_ac || current->delta_q_u_dc ||
+            current->delta_q_v_ac || current->delta_q_v_dc) {
+            priv->coded_lossless = 0;
+        }
+    }
+    priv->all_lossless = priv->coded_lossless &&
+        priv->frame_width == priv->upscaled_width;
+
+    CHECK(FUNC(loop_filter_params)(ctx, rw, current));
+
+    CHECK(FUNC(cdef_params)(ctx, rw, current));
+
+    CHECK(FUNC(lr_params)(ctx, rw, current));
+
+    CHECK(FUNC(read_tx_mode)(ctx, rw, current));
+
+    CHECK(FUNC(frame_reference_mode)(ctx, rw, current));
+
+    CHECK(FUNC(skip_mode_params)(ctx, rw, current));
+
+    if (frame_is_intra || current->error_resilient_mode ||
+        !seq->enable_warped_motion)
+        infer(allow_warped_motion, 0);
+    else
+        flag(allow_warped_motion);
+
+    flag(reduced_tx_set);
+
+    CHECK(FUNC(global_motion_params)(ctx, rw, current));
+
+    CHECK(FUNC(film_grain_params)(ctx, rw, current));
+
+    for (i = 0; i < AV1_NUM_REF_FRAMES; i++) {
+        if (current->refresh_frame_flags & (1 << i)) {
+            priv->ref[i] = (AV1ReferenceFrameState) {
+                .valid          = 1,
+                .frame_id       = current->current_frame_id,
+                .upscaled_width = priv->upscaled_width,
+                .frame_width    = priv->frame_width,
+                .frame_height   = priv->frame_height,
+                .render_width   = priv->render_width,
+                .render_height  = priv->render_height,
+                .frame_type     = current->frame_type,
+                .subsampling_x  = seq->color_config.subsampling_x,
+                .subsampling_y  = seq->color_config.subsampling_y,
+                .bit_depth      = priv->bit_depth,
+                .order_hint     = current->order_hint,
+            };
+        }
+    }
+
+    av_log(ctx->log_ctx, AV_LOG_DEBUG, "Frame %d:  size %dx%d  "
+           "upscaled %d  render %dx%d  subsample %dx%d  "
+           "bitdepth %d  tiles %dx%d.\n", current->order_hint,
+           priv->frame_width, priv->frame_height, priv->upscaled_width,
+           priv->render_width, priv->render_height,
+           seq->color_config.subsampling_x + 1,
+           seq->color_config.subsampling_y + 1, priv->bit_depth,
+           priv->tile_rows, priv->tile_cols);
+
+    return 0;
+}
+
+static int FUNC(frame_header_obu)(CodedBitstreamContext *ctx, RWContext *rw,
+                                  AV1RawFrameHeader *current)
+{
+    CodedBitstreamAV1Context *priv = ctx->priv_data;
+    int err;
+
+    HEADER("Frame Header");
+
+    if (priv->seen_frame_header) {
+        // Nothing to do.
+    } else {
+        priv->seen_frame_header = 1;
+
+        CHECK(FUNC(uncompressed_header)(ctx, rw, current));
+
+        if (current->show_existing_frame) {
+            priv->seen_frame_header = 0;
+        } else {
+            priv->seen_frame_header = 1;
+        }
+    }
+
+    return 0;
+}
+
+static int FUNC(tile_group_obu)(CodedBitstreamContext *ctx, RWContext *rw,
+                                AV1RawTileGroup *current)
+{
+    CodedBitstreamAV1Context *priv = ctx->priv_data;
+    int num_tiles, tile_bits;
+    int err;
+
+    HEADER("Tile Group");
+
+    num_tiles = priv->tile_cols * priv->tile_rows;
+    if (num_tiles > 1)
+        flag(tile_start_and_end_present_flag);
+    else
+        infer(tile_start_and_end_present_flag, 0);
+
+    if (num_tiles == 1 || !current->tile_start_and_end_present_flag) {
+        infer(tg_start, 0);
+        infer(tg_end, num_tiles - 1);
+    } else {
+        tile_bits = cbs_av1_tile_log2(1, priv->tile_cols) +
+                    cbs_av1_tile_log2(1, priv->tile_rows);
+        fb(tile_bits, tg_start);
+        fb(tile_bits, tg_end);
+    }
+
+    CHECK(FUNC(byte_alignment)(ctx, rw));
+
+    // Reset header for next frame.
+    if (current->tg_end == num_tiles - 1)
+        priv->seen_frame_header = 0;
+
+    // Tile data follows.
+
+    return 0;
+}
+
+static int FUNC(frame_obu)(CodedBitstreamContext *ctx, RWContext *rw,
+                           AV1RawFrame *current)
+{
+    int err;
+
+    CHECK(FUNC(frame_header_obu)(ctx, rw, &current->header));
+
+    CHECK(FUNC(byte_alignment)(ctx, rw));
+
+    CHECK(FUNC(tile_group_obu)(ctx, rw, &current->tile_group));
+
+    return 0;
+}
+
+static int FUNC(tile_list_obu)(CodedBitstreamContext *ctx, RWContext *rw,
+                               AV1RawTileList *current)
+{
+    int err;
+
+    fb(8, output_frame_width_in_tiles_minus_1);
+    fb(8, output_frame_height_in_tiles_minus_1);
+
+    fb(16, tile_count_minus_1);
+
+    // Tile data follows.
+
+    return 0;
+}
+
+static int FUNC(metadata_hdr_cll)(CodedBitstreamContext *ctx, RWContext *rw,
+                                  AV1RawMetadataHDRCLL *current)
+{
+    int err;
+
+    fb(16, max_cll);
+    fb(16, max_fall);
+
+    return 0;
+}
+
+static int FUNC(metadata_hdr_mdcv)(CodedBitstreamContext *ctx, RWContext *rw,
+                                   AV1RawMetadataHDRMDCV *current)
+{
+    int err, i;
+
+    for (i = 0; i < 3; i++) {
+        fcs(16, primary_chromaticity_x[i], 0, 50000, 1, i);
+        fcs(16, primary_chromaticity_y[i], 0, 50000, 1, i);
+    }
+
+    fc(16, white_point_chromaticity_x, 0, 50000);
+    fc(16, white_point_chromaticity_y, 0, 50000);
+
+    fc(32, luminance_max, 1, MAX_UINT_BITS(32));
+    fc(32, luminance_min, 0, current->luminance_max >> 6);
+
+    return 0;
+}
+
+static int FUNC(metadata_scalability)(CodedBitstreamContext *ctx, RWContext *rw,
+                                      AV1RawMetadataScalability *current)
+{
+    // TODO: scalability metadata.
+
+    return AVERROR_PATCHWELCOME;
+}
+
+static int FUNC(metadata_itut_t35)(CodedBitstreamContext *ctx, RWContext *rw,
+                                   AV1RawMetadataITUTT35 *current)
+{
+    int err;
+    size_t i;
+
+    fb(8, itu_t_t35_country_code);
+    if (current->itu_t_t35_country_code == 0xff)
+        fb(8, itu_t_t35_country_code_extension_byte);
+
+#ifdef READ
+    // The payload runs up to the start of the trailing bits, but there might
+    // be arbitrarily many trailing zeroes so we need to read through twice.
+    {
+        GetBitContext tmp = *rw;
+        current->payload_size = 0;
+        for (i = 0; get_bits_left(rw) >= 8; i++) {
+            if (get_bits(rw, 8))
+                current->payload_size = i;
+        }
+        *rw = tmp;
+    }
+
+    current->payload_ref = av_buffer_alloc(current->payload_size);
+    if (!current->payload_ref)
+        return AVERROR(ENOMEM);
+    current->payload = current->payload_ref->data;
+#endif
+
+    for (i = 0; i < current->payload_size; i++)
+        xf(8, itu_t_t35_payload_bytes[i], current->payload[i],
+           0x00, 0xff, 1, i);
+
+    return 0;
+}
+
+static int FUNC(metadata_timecode)(CodedBitstreamContext *ctx, RWContext *rw,
+                                   AV1RawMetadataTimecode *current)
+{
+    int err;
+
+    fb(5, counting_type);
+    flag(full_timestamp_flag);
+    flag(discontinuity_flag);
+    flag(cnt_dropped_flag);
+    fb(9, n_frames);
+
+    if (current->full_timestamp_flag) {
+        fb(6, seconds_value);
+        fb(6, minutes_value);
+        fb(5, hours_value);
+    } else {
+        flag(seconds_flag);
+        if (current->seconds_flag) {
+            fb(6, seconds_value);
+            flag(minutes_flag);
+            if (current->minutes_flag) {
+                fb(6, minutes_value);
+                flag(hours_flag);
+                if (current->hours_flag)
+                    fb(5, hours_value);
+            }
+        }
+    }
+
+    fb(5, time_offset_length);
+    if (current->time_offset_length > 0)
+        fb(current->time_offset_length, time_offset_value);
+
+    return 0;
+}
+
+static int FUNC(metadata_obu)(CodedBitstreamContext *ctx, RWContext *rw,
+                              AV1RawMetadata *current)
+{
+    int err;
+
+    leb128(metadata_type);
+
+    switch (current->metadata_type) {
+    case AV1_METADATA_TYPE_HDR_CLL:
+        CHECK(FUNC(metadata_hdr_cll)(ctx, rw, &current->metadata.hdr_cll));
+        break;
+    case AV1_METADATA_TYPE_HDR_MDCV:
+        CHECK(FUNC(metadata_hdr_mdcv)(ctx, rw, &current->metadata.hdr_mdcv));
+        break;
+    case AV1_METADATA_TYPE_SCALABILITY:
+        CHECK(FUNC(metadata_scalability)(ctx, rw, &current->metadata.scalability));
+        break;
+    case AV1_METADATA_TYPE_ITUT_T35:
+        CHECK(FUNC(metadata_itut_t35)(ctx, rw, &current->metadata.itut_t35));
+        break;
+    case AV1_METADATA_TYPE_TIMECODE:
+        CHECK(FUNC(metadata_timecode)(ctx, rw, &current->metadata.timecode));
+        break;
+    default:
+        // Unknown metadata type.
+        return AVERROR_PATCHWELCOME;
+    }
+
+    return 0;
+}
diff --git a/libavcodec/cbs_internal.h b/libavcodec/cbs_internal.h
index 172b8a2515..f074a4affc 100644
--- a/libavcodec/cbs_internal.h
+++ b/libavcodec/cbs_internal.h
@@ -86,6 +86,7 @@ int ff_cbs_write_unsigned(CodedBitstreamContext *ctx, PutBitContext *pbc,
 #define MAX_UINT_BITS(length) ((UINT64_C(1) << (length)) - 1)
 
 
+extern const CodedBitstreamType ff_cbs_type_av1;
 extern const CodedBitstreamType ff_cbs_type_h264;
 extern const CodedBitstreamType ff_cbs_type_h265;
 extern const CodedBitstreamType ff_cbs_type_mpeg2;
