diff --git a/configure b/configure
index 0f002dc6eb..57748e1424 100755
--- a/configure
+++ b/configure
@@ -2236,6 +2236,7 @@ CONFIG_EXTRA="
     cbs_h264
     cbs_h265
     cbs_mpeg2
+    cbs_vp9
     dirac_parse
     dvprofile
     exif
@@ -2497,6 +2498,7 @@ threads_if_any="$THREADS_LIST"
 cbs_h264_select="cbs golomb"
 cbs_h265_select="cbs golomb"
 cbs_mpeg2_select="cbs"
+cbs_vp9_select="cbs"
 dct_select="rdft"
 dirac_parse_select="golomb"
 error_resilience_select="me_cmp"
diff --git a/doc/bitstream_filters.texi b/doc/bitstream_filters.texi
index 7322af6550..7f98cb714f 100644
--- a/doc/bitstream_filters.texi
+++ b/doc/bitstream_filters.texi
@@ -505,7 +505,7 @@ Log trace output containing all syntax elements in the coded stream
 headers (everything above the level of individual coded blocks).
 This can be useful for debugging low-level stream issues.
 
-Supports H.264, H.265 and MPEG-2.
+Supports H.264, H.265, MPEG-2 and VP9.
 
 @section vp9_superframe
 
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index d727b218dc..15e8c87385 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -65,6 +65,7 @@ OBJS-$(CONFIG_CBS)                     += cbs.o
 OBJS-$(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
+OBJS-$(CONFIG_CBS_VP9)                 += cbs_vp9.o
 OBJS-$(CONFIG_CRYSTALHD)               += crystalhd.o
 OBJS-$(CONFIG_DCT)                     += dct.o dct32_fixed.o dct32_float.o
 OBJS-$(CONFIG_ERROR_RESILIENCE)        += error_resilience.o
diff --git a/libavcodec/cbs.c b/libavcodec/cbs.c
index 7091c9abf5..2c0198f799 100644
--- a/libavcodec/cbs.c
+++ b/libavcodec/cbs.c
@@ -38,6 +38,9 @@ static const CodedBitstreamType *cbs_type_table[] = {
 #if CONFIG_CBS_MPEG2
     &ff_cbs_type_mpeg2,
 #endif
+#if CONFIG_CBS_VP9
+    &ff_cbs_type_vp9,
+#endif
 };
 
 const enum AVCodecID ff_cbs_all_codec_ids[] = {
@@ -49,6 +52,9 @@ const enum AVCodecID ff_cbs_all_codec_ids[] = {
 #endif
 #if CONFIG_CBS_MPEG2
     AV_CODEC_ID_MPEG2VIDEO,
+#endif
+#if CONFIG_CBS_VP9
+    AV_CODEC_ID_VP9,
 #endif
     AV_CODEC_ID_NONE
 };
diff --git a/libavcodec/cbs.h b/libavcodec/cbs.h
index 487358afaf..53ac360bb1 100644
--- a/libavcodec/cbs.h
+++ b/libavcodec/cbs.h
@@ -48,6 +48,7 @@ struct CodedBitstreamType;
  * H.264 / AVC: nal_unit_type
  * H.265 / HEVC: nal_unit_type
  * MPEG-2: start code value (without prefix)
+ * VP9: unused, set to zero (every unit is a frame)
  */
 typedef uint32_t CodedBitstreamUnitType;
 
diff --git a/libavcodec/cbs_internal.h b/libavcodec/cbs_internal.h
index 3280e7602d..172b8a2515 100644
--- a/libavcodec/cbs_internal.h
+++ b/libavcodec/cbs_internal.h
@@ -89,6 +89,7 @@ int ff_cbs_write_unsigned(CodedBitstreamContext *ctx, PutBitContext *pbc,
 extern const CodedBitstreamType ff_cbs_type_h264;
 extern const CodedBitstreamType ff_cbs_type_h265;
 extern const CodedBitstreamType ff_cbs_type_mpeg2;
+extern const CodedBitstreamType ff_cbs_type_vp9;
 
 
 #endif /* AVCODEC_CBS_INTERNAL_H */
diff --git a/libavcodec/cbs_vp9.c b/libavcodec/cbs_vp9.c
new file mode 100644
index 0000000000..7498be4b73
--- /dev/null
+++ b/libavcodec/cbs_vp9.c
@@ -0,0 +1,679 @@
+/*
+ * 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 "cbs.h"
+#include "cbs_internal.h"
+#include "cbs_vp9.h"
+#include "internal.h"
+
+
+static int cbs_vp9_read_s(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_vp9_write_s(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_vp9_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[8];
+
+    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_vp9_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 < 8);
+    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[8];
+        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_vp9_read_le(CodedBitstreamContext *ctx, GetBitContext *gbc,
+                           int width, const char *name,
+                           const int *subscripts, uint32_t *write_to)
+{
+    uint32_t value;
+    int position, b;
+
+    av_assert0(width % 8 == 0);
+
+    if (ctx->trace_enable)
+        position = get_bits_count(gbc);
+
+    if (get_bits_left(gbc) < width) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid le value at "
+               "%s: bitstream ended.\n", name);
+        return AVERROR_INVALIDDATA;
+    }
+
+    value = 0;
+    for (b = 0; b < width; b += 8)
+        value |= get_bits(gbc, 8) << b;
+
+    if (ctx->trace_enable) {
+        char bits[33];
+        int i;
+        for (b = 0; b < width; b += 8)
+            for (i = 0; i < 8; i++)
+                bits[b + i] = value >> (b + i) & 1 ? '1' : '0';
+        bits[b] = 0;
+
+        ff_cbs_trace_syntax_element(ctx, position, name, subscripts,
+                                    bits, value);
+    }
+
+    *write_to = value;
+    return 0;
+}
+
+static int cbs_vp9_write_le(CodedBitstreamContext *ctx, PutBitContext *pbc,
+                            int width, const char *name,
+                            const int *subscripts, uint32_t value)
+{
+    int b;
+
+    av_assert0(width % 8 == 0);
+
+    if (put_bits_left(pbc) < width)
+        return AVERROR(ENOSPC);
+
+    if (ctx->trace_enable) {
+        char bits[33];
+        int i;
+        for (b = 0; b < width; b += 8)
+            for (i = 0; i < 8; i++)
+                bits[b + i] = value >> (b + i) & 1 ? '1' : '0';
+        bits[b] = 0;
+
+        ff_cbs_trace_syntax_element(ctx, put_bits_count(pbc),
+                                    name, subscripts, bits, value);
+    }
+
+    for (b = 0; b < width; b += 8)
+        put_bits(pbc, 8, value >> b & 0xff);
+
+    return 0;
+}
+
+#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_VP9(rw, name) FUNC_NAME(rw, vp9, name)
+#define FUNC(name) FUNC_VP9(READWRITE, name)
+
+#define SUBSCRIPTS(subs, ...) (subs > 0 ? ((int[subs + 1]){ subs, __VA_ARGS__ }) : NULL)
+
+#define f(width, name) \
+        xf(width, name, current->name, 0)
+#define s(width, name) \
+        xs(width, name, current->name, 0)
+#define fs(width, name, subs, ...) \
+        xf(width, name, current->name, subs, __VA_ARGS__)
+#define ss(width, name, subs, ...) \
+        xs(width, name, current->name, subs, __VA_ARGS__)
+
+
+#define READ
+#define READWRITE read
+#define RWContext GetBitContext
+
+#define xf(width, name, var, subs, ...) do { \
+        uint32_t value = 0; \
+        CHECK(ff_cbs_read_unsigned(ctx, rw, width, #name, \
+                                   SUBSCRIPTS(subs, __VA_ARGS__), \
+                                   &value, 0, (1 << width) - 1)); \
+        var = value; \
+    } while (0)
+#define xs(width, name, var, subs, ...) do { \
+        int32_t value = 0; \
+        CHECK(cbs_vp9_read_s(ctx, rw, width, #name, \
+                             SUBSCRIPTS(subs, __VA_ARGS__), &value)); \
+        var = value; \
+    } while (0)
+
+
+#define increment(name, min, max) do { \
+        uint32_t value = 0; \
+        CHECK(cbs_vp9_read_increment(ctx, rw, min, max, #name, &value)); \
+        current->name = value; \
+    } while (0)
+
+#define fle(width, name, subs, ...) do { \
+        CHECK(cbs_vp9_read_le(ctx, rw, width, #name, \
+                              SUBSCRIPTS(subs, __VA_ARGS__), &current->name)); \
+    } while (0)
+
+#define delta_q(name) do { \
+        uint8_t delta_coded; \
+        int8_t delta_q; \
+        xf(1, name.delta_coded, delta_coded, 0); \
+        if (delta_coded) \
+            xs(4, name.delta_q, delta_q, 0); \
+        else \
+            delta_q = 0; \
+        current->name = delta_q; \
+    } while (0)
+
+#define prob(name, subs, ...) do { \
+        uint8_t prob_coded; \
+        int8_t prob; \
+        xf(1, name.prob_coded, prob_coded, subs, __VA_ARGS__); \
+        if (prob_coded) \
+            xf(8, name.prob, prob, subs, __VA_ARGS__); \
+        else \
+            prob = 255; \
+        current->name = prob; \
+    } while (0)
+
+#define infer(name, value) do { \
+        current->name = value; \
+    } while (0)
+
+#define byte_alignment(rw) (get_bits_count(rw) % 8)
+
+#include "cbs_vp9_syntax_template.c"
+
+#undef READ
+#undef READWRITE
+#undef RWContext
+#undef xf
+#undef xs
+#undef increment
+#undef fle
+#undef delta_q
+#undef prob
+#undef infer
+#undef byte_alignment
+
+
+#define WRITE
+#define READWRITE write
+#define RWContext PutBitContext
+
+#define xf(width, name, var, subs, ...) do { \
+        CHECK(ff_cbs_write_unsigned(ctx, rw, width, #name, \
+                                    SUBSCRIPTS(subs, __VA_ARGS__), \
+                                    var, 0, (1 << width) - 1)); \
+    } while (0)
+#define xs(width, name, var, subs, ...) do { \
+        CHECK(cbs_vp9_write_s(ctx, rw, width, #name, \
+                              SUBSCRIPTS(subs, __VA_ARGS__), var)); \
+    } while (0)
+
+#define increment(name, min, max) do { \
+        CHECK(cbs_vp9_write_increment(ctx, rw, min, max, #name, current->name)); \
+    } while (0)
+
+#define fle(width, name, subs, ...) do { \
+        CHECK(cbs_vp9_write_le(ctx, rw, width, #name, \
+                               SUBSCRIPTS(subs, __VA_ARGS__), current->name)); \
+    } while (0)
+
+#define delta_q(name) do { \
+        xf(1, name.delta_coded, !!current->name, 0); \
+        if (current->name) \
+            xs(4, name.delta_q, current->name, 0); \
+    } while (0)
+
+#define prob(name, subs, ...) do { \
+        xf(1, name.prob_coded, current->name != 255, subs, __VA_ARGS__); \
+        if (current->name != 255) \
+            xf(8, name.prob, current->name, subs, __VA_ARGS__); \
+    } 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_vp9_syntax_template.c"
+
+#undef READ
+#undef READWRITE
+#undef RWContext
+#undef xf
+#undef xs
+#undef increment
+#undef fle
+#undef delta_q
+#undef prob
+#undef infer
+#undef byte_alignment
+
+
+static int cbs_vp9_split_fragment(CodedBitstreamContext *ctx,
+                                  CodedBitstreamFragment *frag,
+                                  int header)
+{
+    uint8_t superframe_header;
+    int err;
+
+    // Last byte in the packet.
+    superframe_header = frag->data[frag->data_size - 1];
+
+    if ((superframe_header & 0xe0) == 0xc0) {
+        VP9RawSuperframeIndex sfi;
+        GetBitContext gbc;
+        size_t index_size, pos;
+        int i;
+
+        index_size = 2 + (((superframe_header & 0x18) >> 3) + 1) *
+                          ((superframe_header & 0x07) + 1);
+
+        err = init_get_bits(&gbc, frag->data + frag->data_size - index_size,
+                            8 * index_size);
+        if (err < 0)
+            return err;
+
+        err = cbs_vp9_read_superframe_index(ctx, &gbc, &sfi);
+        if (err < 0)
+            return err;
+
+        pos = 0;
+        for (i = 0; i <= sfi.frames_in_superframe_minus_1; i++) {
+            if (pos + sfi.frame_sizes[i] + index_size > frag->data_size) {
+                av_log(ctx->log_ctx, AV_LOG_ERROR, "Frame %d too large "
+                       "in superframe: %"PRIu32" bytes.\n",
+                       i, sfi.frame_sizes[i]);
+                return AVERROR_INVALIDDATA;
+            }
+
+            err = ff_cbs_insert_unit_data(ctx, frag, -1, 0,
+                                          frag->data + pos,
+                                          sfi.frame_sizes[i],
+                                          frag->data_ref);
+            if (err < 0)
+                return err;
+
+            pos += sfi.frame_sizes[i];
+        }
+        if (pos + index_size != frag->data_size) {
+            av_log(ctx->log_ctx, AV_LOG_WARNING, "Extra padding at "
+                   "end of superframe: %zu bytes.\n",
+                   frag->data_size - (pos + index_size));
+        }
+
+        return 0;
+
+    } else {
+        err = ff_cbs_insert_unit_data(ctx, frag, -1, 0,
+                                      frag->data, frag->data_size,
+                                      frag->data_ref);
+        if (err < 0)
+            return err;
+    }
+
+    return 0;
+}
+
+static void cbs_vp9_free_frame(void *unit, uint8_t *content)
+{
+    VP9RawFrame *frame = (VP9RawFrame*)content;
+    av_buffer_unref(&frame->data_ref);
+    av_freep(&frame);
+}
+
+static int cbs_vp9_read_unit(CodedBitstreamContext *ctx,
+                             CodedBitstreamUnit *unit)
+{
+    VP9RawFrame *frame;
+    GetBitContext gbc;
+    int err, pos;
+
+    err = init_get_bits(&gbc, unit->data, 8 * unit->data_size);
+    if (err < 0)
+        return err;
+
+    err = ff_cbs_alloc_unit_content(ctx, unit, sizeof(*frame),
+                                    &cbs_vp9_free_frame);
+    if (err < 0)
+        return err;
+    frame = unit->content;
+
+    err = cbs_vp9_read_frame(ctx, &gbc, frame);
+    if (err < 0)
+        return err;
+
+    pos = get_bits_count(&gbc);
+    av_assert0(pos % 8 == 0);
+    pos /= 8;
+    av_assert0(pos <= unit->data_size);
+
+    if (pos == unit->data_size) {
+        // No data (e.g. a show-existing-frame frame).
+    } else {
+        frame->data_ref = av_buffer_ref(unit->data_ref);
+        if (!frame->data_ref)
+            return AVERROR(ENOMEM);
+
+        frame->data      = unit->data      + pos;
+        frame->data_size = unit->data_size - pos;
+    }
+
+    return 0;
+}
+
+static int cbs_vp9_write_unit(CodedBitstreamContext *ctx,
+                              CodedBitstreamUnit *unit)
+{
+    CodedBitstreamVP9Context *priv = ctx->priv_data;
+    VP9RawFrame *frame = unit->content;
+    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_vp9_write_frame(ctx, &pbc, frame);
+    if (err == AVERROR(ENOSPC)) {
+        priv->write_buffer_size *= 2;
+        goto reallocate_and_try_again;
+    }
+    if (err < 0)
+        return err;
+
+    // Frame must be byte-aligned.
+    av_assert0(put_bits_count(&pbc) % 8 == 0);
+
+    unit->data_size        = put_bits_count(&pbc) / 8;
+    unit->data_bit_padding = 0;
+    flush_put_bits(&pbc);
+
+    if (frame->data) {
+        if (unit->data_size + frame->data_size >
+            priv->write_buffer_size) {
+            priv->write_buffer_size *= 2;
+            goto reallocate_and_try_again;
+        }
+
+        memcpy(priv->write_buffer + unit->data_size,
+               frame->data, frame->data_size);
+        unit->data_size += frame->data_size;
+    }
+
+    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_vp9_assemble_fragment(CodedBitstreamContext *ctx,
+                                     CodedBitstreamFragment *frag)
+{
+    int err;
+
+    if (frag->nb_units == 1) {
+        // Output is just the content of the single frame.
+
+        CodedBitstreamUnit *frame = &frag->units[0];
+
+        frag->data_ref = av_buffer_ref(frame->data_ref);
+        if (!frag->data_ref)
+            return AVERROR(ENOMEM);
+
+        frag->data      = frame->data;
+        frag->data_size = frame->data_size;
+
+    } else {
+        // Build superframe out of frames.
+
+        VP9RawSuperframeIndex sfi;
+        PutBitContext pbc;
+        AVBufferRef *ref;
+        uint8_t *data;
+        size_t size, max, pos;
+        int i, size_len;
+
+        if (frag->nb_units > 8) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Too many frames to "
+                   "make superframe: %d.\n", frag->nb_units);
+            return AVERROR(EINVAL);
+        }
+
+        max = 0;
+        for (i = 0; i < frag->nb_units; i++)
+            if (max < frag->units[i].data_size)
+                max = frag->units[i].data_size;
+
+        if (max < 2)
+            size_len = 1;
+        else
+            size_len = av_log2(max) / 8 + 1;
+        av_assert0(size_len <= 4);
+
+        sfi.superframe_marker            = VP9_SUPERFRAME_MARKER;
+        sfi.bytes_per_framesize_minus_1  = size_len - 1;
+        sfi.frames_in_superframe_minus_1 = frag->nb_units - 1;
+
+        size = 2;
+        for (i = 0; i < frag->nb_units; i++) {
+            size += size_len + frag->units[i].data_size;
+            sfi.frame_sizes[i] = frag->units[i].data_size;
+        }
+
+        ref = av_buffer_alloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
+        if (!ref)
+            return AVERROR(ENOMEM);
+        data = ref->data;
+        memset(data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
+
+        pos = 0;
+        for (i = 0; i < frag->nb_units; i++) {
+            av_assert0(size - pos > frag->units[i].data_size);
+            memcpy(data + pos, frag->units[i].data,
+                   frag->units[i].data_size);
+            pos += frag->units[i].data_size;
+        }
+        av_assert0(size - pos == 2 + frag->nb_units * size_len);
+
+        init_put_bits(&pbc, data + pos, size - pos);
+
+        err = cbs_vp9_write_superframe_index(ctx, &pbc, &sfi);
+        if (err < 0) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Failed to write "
+                   "superframe index.\n");
+            av_buffer_unref(&ref);
+            return err;
+        }
+
+        av_assert0(put_bits_left(&pbc) == 0);
+        flush_put_bits(&pbc);
+
+        frag->data_ref  = ref;
+        frag->data      = data;
+        frag->data_size = size;
+    }
+
+    return 0;
+}
+
+static void cbs_vp9_close(CodedBitstreamContext *ctx)
+{
+    CodedBitstreamVP9Context *priv = ctx->priv_data;
+
+    av_freep(&priv->write_buffer);
+}
+
+const CodedBitstreamType ff_cbs_type_vp9 = {
+    .codec_id          = AV_CODEC_ID_VP9,
+
+    .priv_data_size    = sizeof(CodedBitstreamVP9Context),
+
+    .split_fragment    = &cbs_vp9_split_fragment,
+    .read_unit         = &cbs_vp9_read_unit,
+    .write_unit        = &cbs_vp9_write_unit,
+    .assemble_fragment = &cbs_vp9_assemble_fragment,
+
+    .close             = &cbs_vp9_close,
+};
diff --git a/libavcodec/cbs_vp9.h b/libavcodec/cbs_vp9.h
new file mode 100644
index 0000000000..5b99c90c2e
--- /dev/null
+++ b/libavcodec/cbs_vp9.h
@@ -0,0 +1,201 @@
+/*
+ * 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_VP9_H
+#define AVCODEC_CBS_VP9_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "cbs.h"
+
+
+// Miscellaneous constants (section 3).
+enum {
+    VP9_REFS_PER_FRAME = 3,
+
+    VP9_MIN_TILE_WIDTH_B64 = 4,
+    VP9_MAX_TILE_WIDTH_B64 = 64,
+
+    VP9_NUM_REF_FRAMES = 8,
+    VP9_MAX_REF_FRAMES = 4,
+
+    VP9_MAX_SEGMENTS = 8,
+    VP9_SEG_LVL_MAX  = 4,
+};
+
+// Frame types (section 7.2).
+enum {
+    VP9_KEY_FRAME     = 0,
+    VP9_NON_KEY_FRAME = 1,
+};
+
+// Frame sync bytes (section 7.2.1).
+enum {
+    VP9_FRAME_SYNC_0 = 0x49,
+    VP9_FRAME_SYNC_1 = 0x83,
+    VP9_FRAME_SYNC_2 = 0x42,
+};
+
+// Color space values (section 7.2.2).
+enum {
+    VP9_CS_UNKNOWN   = 0,
+    VP9_CS_BT_601    = 1,
+    VP9_CS_BT_709    = 2,
+    VP9_CS_SMPTE_170 = 3,
+    VP9_CS_SMPTE_240 = 4,
+    VP9_CS_BT_2020   = 5,
+    VP9_CS_RESERVED  = 6,
+    VP9_CS_RGB       = 7,
+};
+
+// Reference frame types (section 7.4.12).
+enum {
+    VP9_INTRA_FRAME  = 0,
+    VP9_LAST_FRAME   = 1,
+    VP9_GOLDEN_FRAME = 2,
+    VP9_ALTREF_FRAME = 3,
+};
+
+// Superframe properties (section B.3).
+enum {
+    VP9_MAX_FRAMES_IN_SUPERFRAME = 8,
+
+    VP9_SUPERFRAME_MARKER = 6,
+};
+
+
+typedef struct VP9RawFrameHeader {
+    uint8_t frame_marker;
+    uint8_t profile_low_bit;
+    uint8_t profile_high_bit;
+    uint8_t profile_reserved_zero;
+
+    uint8_t show_existing_frame;
+    uint8_t frame_to_show_map_idx;
+
+    uint8_t frame_type;
+    uint8_t show_frame;
+    uint8_t error_resilient_mode;
+
+    // Color config.
+    uint8_t ten_or_twelve_bit;
+    uint8_t color_space;
+    uint8_t color_range;
+    uint8_t subsampling_x;
+    uint8_t subsampling_y;
+    uint8_t color_config_reserved_zero;
+
+    uint8_t refresh_frame_flags;
+
+    uint8_t intra_only;
+    uint8_t reset_frame_context;
+
+    uint8_t ref_frame_idx[VP9_REFS_PER_FRAME];
+    uint8_t ref_frame_sign_bias[VP9_MAX_REF_FRAMES];
+
+    uint8_t allow_high_precision_mv;
+
+    uint8_t refresh_frame_context;
+    uint8_t frame_parallel_decoding_mode;
+
+    uint8_t frame_context_idx;
+
+    // Frame/render size.
+    uint8_t found_ref[VP9_REFS_PER_FRAME];
+    uint16_t frame_width_minus_1;
+    uint16_t frame_height_minus_1;
+    uint8_t render_and_frame_size_different;
+    uint16_t render_width_minus_1;
+    uint16_t render_height_minus_1;
+
+    // Interpolation filter.
+    uint8_t is_filter_switchable;
+    uint8_t raw_interpolation_filter_type;
+
+    // Loop filter params.
+    uint8_t loop_filter_level;
+    uint8_t loop_filter_sharpness;
+    uint8_t loop_filter_delta_enabled;
+    uint8_t loop_filter_delta_update;
+    uint8_t update_ref_delta[VP9_MAX_REF_FRAMES];
+    int8_t loop_filter_ref_deltas[VP9_MAX_REF_FRAMES];
+    uint8_t update_mode_delta[2];
+    int8_t loop_filter_mode_deltas[2];
+
+    // Quantization params.
+    uint8_t base_q_idx;
+    int8_t delta_q_y_dc;
+    int8_t delta_q_uv_dc;
+    int8_t delta_q_uv_ac;
+
+    // Segmentation params.
+    uint8_t segmentation_enabled;
+    uint8_t segmentation_update_map;
+    uint8_t segmentation_tree_probs[7];
+    uint8_t segmentation_temporal_update;
+    uint8_t segmentation_pred_prob[3];
+    uint8_t segmentation_update_data;
+    uint8_t segmentation_abs_or_delta_update;
+    uint8_t feature_enabled[VP9_MAX_SEGMENTS][VP9_SEG_LVL_MAX];
+    uint8_t feature_value[VP9_MAX_SEGMENTS][VP9_SEG_LVL_MAX];
+    uint8_t feature_sign[VP9_MAX_SEGMENTS][VP9_SEG_LVL_MAX];
+
+    // Tile info.
+    uint8_t tile_cols_log2;
+    uint8_t tile_rows_log2;
+
+    uint16_t header_size_in_bytes;
+} VP9RawFrameHeader;
+
+typedef struct VP9RawFrame {
+    VP9RawFrameHeader header;
+
+    uint8_t     *data;
+    size_t       data_size;
+    AVBufferRef *data_ref;
+} VP9RawFrame;
+
+typedef struct VP9RawSuperframeIndex {
+    uint8_t superframe_marker;
+    uint8_t bytes_per_framesize_minus_1;
+    uint8_t frames_in_superframe_minus_1;
+    uint32_t frame_sizes[VP9_MAX_FRAMES_IN_SUPERFRAME];
+} VP9RawSuperframeIndex;
+
+typedef struct VP9RawSuperframe {
+    VP9RawFrame frames[VP9_MAX_FRAMES_IN_SUPERFRAME];
+    VP9RawSuperframeIndex index;
+} VP9RawSuperframe;
+
+
+typedef struct CodedBitstreamVP9Context {
+    // Frame dimensions in 8x8 mode info blocks.
+    uint16_t mi_cols;
+    uint16_t mi_rows;
+    // Frame dimensions in 64x64 superblocks.
+    uint16_t sb64_cols;
+    uint16_t sb64_rows;
+
+    // Write buffer.
+    uint8_t *write_buffer;
+    size_t write_buffer_size;
+} CodedBitstreamVP9Context;
+
+
+#endif /* AVCODEC_CBS_VP9_H */
diff --git a/libavcodec/cbs_vp9_syntax_template.c b/libavcodec/cbs_vp9_syntax_template.c
new file mode 100644
index 0000000000..0db0f52a6d
--- /dev/null
+++ b/libavcodec/cbs_vp9_syntax_template.c
@@ -0,0 +1,390 @@
+/*
+ * 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(frame_sync_code)(CodedBitstreamContext *ctx, RWContext *rw,
+                                 VP9RawFrameHeader *current)
+{
+    uint8_t frame_sync_byte_0 = VP9_FRAME_SYNC_0;
+    uint8_t frame_sync_byte_1 = VP9_FRAME_SYNC_1;
+    uint8_t frame_sync_byte_2 = VP9_FRAME_SYNC_2;
+    int err;
+
+    xf(8, frame_sync_byte_0, frame_sync_byte_0, 0);
+    xf(8, frame_sync_byte_1, frame_sync_byte_1, 0);
+    xf(8, frame_sync_byte_2, frame_sync_byte_2, 0);
+
+    if (frame_sync_byte_0 != VP9_FRAME_SYNC_0 ||
+        frame_sync_byte_1 != VP9_FRAME_SYNC_1 ||
+        frame_sync_byte_2 != VP9_FRAME_SYNC_2) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid frame sync code: "
+               "%02x %02x %02x.\n", frame_sync_byte_0,
+               frame_sync_byte_1, frame_sync_byte_2);
+        return AVERROR_INVALIDDATA;
+    }
+
+    return 0;
+}
+
+static int FUNC(color_config)(CodedBitstreamContext *ctx, RWContext *rw,
+                              VP9RawFrameHeader *current, int profile)
+{
+    int err;
+
+    if (profile >= 2)
+        f(1, ten_or_twelve_bit);
+
+    f(3, color_space);
+
+    if (current->color_space != VP9_CS_RGB) {
+        f(1, color_range);
+        if (profile == 1 || profile == 3) {
+            f(1, subsampling_x);
+            f(1, subsampling_y);
+            f(1, color_config_reserved_zero);
+        } else {
+            infer(subsampling_x, 1);
+            infer(subsampling_y, 1);
+        }
+    } else {
+        infer(color_range, 1);
+        if (profile == 1 || profile == 3) {
+            infer(subsampling_x, 0);
+            infer(subsampling_y, 0);
+        }
+    }
+
+    return 0;
+}
+
+static int FUNC(frame_size)(CodedBitstreamContext *ctx, RWContext *rw,
+                            VP9RawFrameHeader *current)
+{
+    CodedBitstreamVP9Context *vp9 = ctx->priv_data;
+    int err;
+
+    f(16, frame_width_minus_1);
+    f(16, frame_height_minus_1);
+
+    vp9->mi_cols = (current->frame_width_minus_1  + 8) >> 3;
+    vp9->mi_rows = (current->frame_height_minus_1 + 8) >> 3;
+    vp9->sb64_cols = (vp9->mi_cols + 7) >> 3;
+    vp9->sb64_rows = (vp9->mi_rows + 7) >> 3;
+
+    return 0;
+}
+
+static int FUNC(render_size)(CodedBitstreamContext *ctx, RWContext *rw,
+                             VP9RawFrameHeader *current)
+{
+    int err;
+
+    f(1, render_and_frame_size_different);
+
+    if (current->render_and_frame_size_different) {
+        f(16, render_width_minus_1);
+        f(16, render_height_minus_1);
+    }
+
+    return 0;
+}
+
+static int FUNC(frame_size_with_refs)(CodedBitstreamContext *ctx, RWContext *rw,
+                                      VP9RawFrameHeader *current)
+{
+    int err, i;
+
+    for (i = 0; i < VP9_REFS_PER_FRAME; i++) {
+        fs(1, found_ref[i], 1, i);
+        if (current->found_ref[i])
+            break;
+    }
+    if (i >= VP9_REFS_PER_FRAME)
+        CHECK(FUNC(frame_size)(ctx, rw, current));
+    CHECK(FUNC(render_size)(ctx, rw, current));
+
+    return 0;
+}
+
+static int FUNC(interpolation_filter)(CodedBitstreamContext *ctx, RWContext *rw,
+                                      VP9RawFrameHeader *current)
+{
+    int err;
+
+    f(1, is_filter_switchable);
+    if (!current->is_filter_switchable)
+        f(2, raw_interpolation_filter_type);
+
+    return 0;
+}
+
+static int FUNC(loop_filter_params)(CodedBitstreamContext *ctx, RWContext *rw,
+                                    VP9RawFrameHeader *current)
+{
+    int err, i;
+
+    f(6, loop_filter_level);
+    f(3, loop_filter_sharpness);
+
+    f(1, loop_filter_delta_enabled);
+    if (current->loop_filter_delta_enabled) {
+        f(1, loop_filter_delta_update);
+        if (current->loop_filter_delta_update) {
+            for (i = 0; i < VP9_MAX_REF_FRAMES; i++) {
+                fs(1, update_ref_delta[i], 1, i);
+                if (current->update_ref_delta[i])
+                    ss(6, loop_filter_ref_deltas[i], 1, i);
+            }
+            for (i = 0; i < 2; i++) {
+                fs(1, update_mode_delta[i], 1, i);
+                if (current->update_mode_delta[i])
+                    ss(6, loop_filter_mode_deltas[i], 1, i);
+            }
+        }
+    }
+
+    return 0;
+}
+
+static int FUNC(quantization_params)(CodedBitstreamContext *ctx, RWContext *rw,
+                                     VP9RawFrameHeader *current)
+{
+    int err;
+
+    f(8, base_q_idx);
+
+    delta_q(delta_q_y_dc);
+    delta_q(delta_q_uv_dc);
+    delta_q(delta_q_uv_ac);
+
+    return 0;
+}
+
+static int FUNC(segmentation_params)(CodedBitstreamContext *ctx, RWContext *rw,
+                                     VP9RawFrameHeader *current)
+{
+    static const int segmentation_feature_bits[VP9_SEG_LVL_MAX]   = { 8, 6, 2, 0 };
+    static const int segmentation_feature_signed[VP9_SEG_LVL_MAX] = { 1, 1, 0, 0 };
+
+    int err, i, j;
+
+    f(1, segmentation_enabled);
+
+    if (current->segmentation_enabled) {
+        f(1, segmentation_update_map);
+        if (current->segmentation_update_map) {
+            for (i = 0; i < 7; i++)
+                prob(segmentation_tree_probs[i], 1, i);
+            f(1, segmentation_temporal_update);
+            for (i = 0; i < 3; i++) {
+                if (current->segmentation_temporal_update)
+                    prob(segmentation_pred_prob[i], 1, i);
+                else
+                    infer(segmentation_pred_prob[i], 255);
+            }
+        }
+
+        f(1, segmentation_update_data);
+        if (current->segmentation_update_data) {
+            f(1, segmentation_abs_or_delta_update);
+            for (i = 0; i < VP9_MAX_SEGMENTS; i++) {
+                for (j = 0; j < VP9_SEG_LVL_MAX; j++) {
+                    fs(1, feature_enabled[i][j], 2, i, j);
+                    if (current->feature_enabled[i][j] &&
+                        segmentation_feature_bits[j]) {
+                        fs(segmentation_feature_bits[j],
+                           feature_value[i][j], 2, i, j);
+                        if (segmentation_feature_signed[j])
+                            fs(1, feature_sign[i][j], 2, i, j);
+                        else
+                            infer(feature_sign[i][j], 0);
+                    } else {
+                        infer(feature_value[i][j], 0);
+                        infer(feature_sign[i][j],  0);
+                    }
+                }
+            }
+        }
+    }
+
+    return 0;
+}
+
+static int FUNC(tile_info)(CodedBitstreamContext *ctx, RWContext *rw,
+                           VP9RawFrameHeader *current)
+{
+    CodedBitstreamVP9Context *vp9 = ctx->priv_data;
+    int min_log2_tile_cols, max_log2_tile_cols;
+    int err;
+
+    min_log2_tile_cols = 0;
+    while ((VP9_MAX_TILE_WIDTH_B64 << min_log2_tile_cols) < vp9->sb64_cols)
+        ++min_log2_tile_cols;
+    max_log2_tile_cols = 0;
+    while ((vp9->sb64_cols >> (max_log2_tile_cols + 1)) >= VP9_MIN_TILE_WIDTH_B64)
+        ++max_log2_tile_cols;
+
+    increment(tile_cols_log2, min_log2_tile_cols, max_log2_tile_cols);
+
+    increment(tile_rows_log2, 0, 2);
+
+    return 0;
+}
+
+static int FUNC(uncompressed_header)(CodedBitstreamContext *ctx, RWContext *rw,
+                                     VP9RawFrameHeader *current)
+{
+    int profile, i;
+    int err;
+
+    f(2, frame_marker);
+
+    f(1, profile_low_bit);
+    f(1, profile_high_bit);
+    profile = (current->profile_high_bit << 1) + current->profile_low_bit;
+    if (profile == 3)
+        f(1, profile_reserved_zero);
+
+    f(1, show_existing_frame);
+    if (current->show_existing_frame) {
+        f(3, frame_to_show_map_idx);
+        infer(header_size_in_bytes, 0);
+        infer(refresh_frame_flags,  0x00);
+        infer(loop_filter_level,    0);
+        return 0;
+    }
+
+    f(1, frame_type);
+    f(1, show_frame);
+    f(1, error_resilient_mode);
+
+    if (current->frame_type == VP9_KEY_FRAME) {
+        CHECK(FUNC(frame_sync_code)(ctx, rw, current));
+        CHECK(FUNC(color_config)(ctx, rw, current, profile));
+        CHECK(FUNC(frame_size)(ctx, rw, current));
+        CHECK(FUNC(render_size)(ctx, rw, current));
+
+        infer(refresh_frame_flags, 0xff);
+
+    } else {
+         if (current->show_frame == 0)
+             f(1, intra_only);
+         else
+             infer(intra_only, 0);
+
+         if (current->error_resilient_mode == 0)
+             f(2, reset_frame_context);
+         else
+             infer(reset_frame_context, 0);
+
+         if (current->intra_only == 1) {
+             CHECK(FUNC(frame_sync_code)(ctx, rw, current));
+
+             if (profile > 0) {
+                 CHECK(FUNC(color_config)(ctx, rw, current, profile));
+             } else {
+                 infer(color_space,   1);
+                 infer(subsampling_x, 1);
+                 infer(subsampling_y, 1);
+             }
+
+             f(8, refresh_frame_flags);
+
+             CHECK(FUNC(frame_size)(ctx, rw, current));
+             CHECK(FUNC(render_size)(ctx, rw, current));
+         } else {
+             f(8, refresh_frame_flags);
+
+             for (i = 0; i < VP9_REFS_PER_FRAME; i++) {
+                 fs(3, ref_frame_idx[i], 1, i);
+                 fs(1, ref_frame_sign_bias[VP9_LAST_FRAME + i],
+                    1, VP9_LAST_FRAME + i);
+             }
+
+             CHECK(FUNC(frame_size_with_refs)(ctx, rw, current));
+             f(1, allow_high_precision_mv);
+             CHECK(FUNC(interpolation_filter)(ctx, rw, current));
+         }
+    }
+
+    if (current->error_resilient_mode == 0) {
+        f(1, refresh_frame_context);
+        f(1, frame_parallel_decoding_mode);
+    } else {
+        infer(refresh_frame_context,        0);
+        infer(frame_parallel_decoding_mode, 1);
+    }
+
+    f(2, frame_context_idx);
+
+    CHECK(FUNC(loop_filter_params)(ctx, rw, current));
+    CHECK(FUNC(quantization_params)(ctx, rw, current));
+    CHECK(FUNC(segmentation_params)(ctx, rw, current));
+    CHECK(FUNC(tile_info)(ctx, rw, current));
+
+    f(16, header_size_in_bytes);
+
+    return 0;
+}
+
+static int FUNC(trailing_bits)(CodedBitstreamContext *ctx, RWContext *rw)
+{
+    int err;
+    av_unused int zero = 0;
+    while (byte_alignment(rw) != 0)
+        xf(1, zero_bit, zero, 0);
+
+    return 0;
+}
+
+static int FUNC(frame)(CodedBitstreamContext *ctx, RWContext *rw,
+                       VP9RawFrame *current)
+{
+    int err;
+
+    HEADER("Frame");
+
+    CHECK(FUNC(uncompressed_header)(ctx, rw, &current->header));
+
+    CHECK(FUNC(trailing_bits)(ctx, rw));
+
+    return 0;
+}
+
+static int FUNC(superframe_index)(CodedBitstreamContext *ctx, RWContext *rw,
+                                  VP9RawSuperframeIndex *current)
+{
+    int err, i;
+
+    HEADER("Superframe Index");
+
+    f(3, superframe_marker);
+    f(2, bytes_per_framesize_minus_1);
+    f(3, frames_in_superframe_minus_1);
+
+    for (i = 0; i <= current->frames_in_superframe_minus_1; i++) {
+        // Surprise little-endian!
+        fle(8 * (current->bytes_per_framesize_minus_1 + 1),
+            frame_sizes[i], 1, i);
+    }
+
+    f(3, superframe_marker);
+    f(2, bytes_per_framesize_minus_1);
+    f(3, frames_in_superframe_minus_1);
+
+    return 0;
+}
