diff --git a/configure b/configure
index fcdc1974d1..49569315f8 100755
--- a/configure
+++ b/configure
@@ -2151,6 +2151,7 @@ CONFIG_EXTRA="
     bswapdsp
     cabac
     cbs
+    cbs_h264
     dirac_parse
     dvprofile
     exif
@@ -2404,6 +2405,7 @@ w32threads_deps="atomics_native"
 threads_if_any="$THREADS_LIST"
 
 # subsystems
+cbs_h264_select="cbs golomb"
 dct_select="rdft"
 dirac_parse_select="golomb"
 error_resilience_select="me_cmp"
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index 9680553c90..245a44c7d5 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -60,6 +60,7 @@ OBJS-$(CONFIG_BLOCKDSP)                += blockdsp.o
 OBJS-$(CONFIG_BSWAPDSP)                += bswapdsp.o
 OBJS-$(CONFIG_CABAC)                   += cabac.o
 OBJS-$(CONFIG_CBS)                     += cbs.o
+OBJS-$(CONFIG_CBS_H264)                += cbs_h2645.o h2645_parse.o
 OBJS-$(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 fa68040cfa..f489d9806f 100644
--- a/libavcodec/cbs.c
+++ b/libavcodec/cbs.c
@@ -28,6 +28,9 @@
 
 
 static const CodedBitstreamType *cbs_type_table[] = {
+#if CONFIG_CBS_H264
+    &ff_cbs_type_h264,
+#endif
 };
 
 int ff_cbs_init(CodedBitstreamContext **ctx_ptr,
diff --git a/libavcodec/cbs.h b/libavcodec/cbs.h
index 2dc975ed79..a64430667b 100644
--- a/libavcodec/cbs.h
+++ b/libavcodec/cbs.h
@@ -42,6 +42,8 @@ struct CodedBitstreamType;
 
 /**
  * The codec-specific type of a bitstream unit.
+ *
+ * H.264 / AVC: nal_unit_type
  */
 typedef uint32_t CodedBitstreamUnitType;
 
diff --git a/libavcodec/cbs_h264.h b/libavcodec/cbs_h264.h
new file mode 100644
index 0000000000..ab7dfd855f
--- /dev/null
+++ b/libavcodec/cbs_h264.h
@@ -0,0 +1,427 @@
+/*
+ * 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_H264_H
+#define AVCODEC_CBS_H264_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "cbs_h2645.h"
+#include "h264.h"
+
+
+enum {
+    // This limit is arbitrary - it is sufficient for one message of each
+    // type plus some repeats, and will therefore easily cover all sane
+    // streams.  However, it is possible to make technically-valid streams
+    // for which it will fail (for example, by including a large number of
+    // user-data-unregistered messages).
+    H264_MAX_SEI_PAYLOADS = 64,
+};
+
+
+typedef struct H264RawNALUnitHeader {
+    uint8_t forbidden_zero_bit;
+    uint8_t nal_ref_idc;
+    uint8_t nal_unit_type;
+
+    uint8_t svc_extension_flag;
+    uint8_t avc_3d_extension_flag;
+} H264RawNALUnitHeader;
+
+typedef struct H264RawScalingList {
+    int8_t delta_scale[64];
+} H264RawScalingList;
+
+typedef struct H264RawHRD {
+    uint8_t cpb_cnt_minus1;
+    uint8_t bit_rate_scale;
+    uint8_t cpb_size_scale;
+
+    uint32_t bit_rate_value_minus1[H264_MAX_CPB_CNT];
+    uint32_t cpb_size_value_minus1[H264_MAX_CPB_CNT];
+    uint8_t cbr_flag[H264_MAX_CPB_CNT];
+
+    uint8_t initial_cpb_removal_delay_length_minus1;
+    uint8_t cpb_removal_delay_length_minus1;
+    uint8_t dpb_output_delay_length_minus1;
+    uint8_t time_offset_length;
+} H264RawHRD;
+
+typedef struct H264RawVUI {
+    uint8_t aspect_ratio_info_present_flag;
+    uint8_t aspect_ratio_idc;
+    uint16_t sar_width;
+    uint16_t sar_height;
+
+    uint8_t overscan_info_present_flag;
+    uint8_t overscan_appropriate_flag;
+
+    uint8_t video_signal_type_present_flag;
+    uint8_t video_format;
+    uint8_t video_full_range_flag;
+    uint8_t colour_description_present_flag;
+    uint8_t colour_primaries;
+    uint8_t transfer_characteristics;
+    uint8_t matrix_coefficients;
+
+    uint8_t chroma_loc_info_present_flag;
+    uint8_t chroma_sample_loc_type_top_field;
+    uint8_t chroma_sample_loc_type_bottom_field;
+
+    uint8_t timing_info_present_flag;
+    uint32_t num_units_in_tick;
+    uint32_t time_scale;
+    uint8_t fixed_frame_rate_flag;
+
+    uint8_t nal_hrd_parameters_present_flag;
+    H264RawHRD nal_hrd_parameters;
+    uint8_t vcl_hrd_parameters_present_flag;
+    H264RawHRD vcl_hrd_parameters;
+    uint8_t low_delay_hrd_flag;
+
+    uint8_t pic_struct_present_flag;
+
+    uint8_t bitstream_restriction_flag;
+    uint8_t motion_vectors_over_pic_boundaries_flag;
+    uint8_t max_bytes_per_pic_denom;
+    uint8_t max_bits_per_mb_denom;
+    uint8_t log2_max_mv_length_horizontal;
+    uint8_t log2_max_mv_length_vertical;
+    uint8_t max_num_reorder_frames;
+    uint8_t max_dec_frame_buffering;
+} H264RawVUI;
+
+typedef struct H264RawSPS {
+    H264RawNALUnitHeader nal_unit_header;
+
+    uint8_t profile_idc;
+    uint8_t constraint_set0_flag;
+    uint8_t constraint_set1_flag;
+    uint8_t constraint_set2_flag;
+    uint8_t constraint_set3_flag;
+    uint8_t constraint_set4_flag;
+    uint8_t constraint_set5_flag;
+    uint8_t reserved_zero_2bits;
+    uint8_t level_idc;
+
+    uint8_t seq_parameter_set_id;
+
+    uint8_t chroma_format_idc;
+    uint8_t separate_colour_plane_flag;
+    uint8_t bit_depth_luma_minus8;
+    uint8_t bit_depth_chroma_minus8;
+    uint8_t qpprime_y_zero_transform_bypass_flag;
+
+    uint8_t seq_scaling_matrix_present_flag;
+    uint8_t seq_scaling_list_present_flag[12];
+    H264RawScalingList scaling_list_4x4[6];
+    H264RawScalingList scaling_list_8x8[6];
+
+    uint8_t log2_max_frame_num_minus4;
+    uint8_t pic_order_cnt_type;
+    uint8_t log2_max_pic_order_cnt_lsb_minus4;
+    uint8_t delta_pic_order_always_zero_flag;
+    int32_t offset_for_non_ref_pic;
+    int32_t offset_for_top_to_bottom_field;
+    uint8_t num_ref_frames_in_pic_order_cnt_cycle;
+    int32_t offset_for_ref_frame[256];
+
+    uint8_t max_num_ref_frames;
+    uint8_t gaps_in_frame_num_allowed_flag;
+
+    uint16_t pic_width_in_mbs_minus1;
+    uint16_t pic_height_in_map_units_minus1;
+
+    uint8_t frame_mbs_only_flag;
+    uint8_t mb_adaptive_frame_field_flag;
+    uint8_t direct_8x8_inference_flag;
+
+    uint8_t frame_cropping_flag;
+    uint16_t frame_crop_left_offset;
+    uint16_t frame_crop_right_offset;
+    uint16_t frame_crop_top_offset;
+    uint16_t frame_crop_bottom_offset;
+
+    uint8_t vui_parameters_present_flag;
+    H264RawVUI vui;
+} H264RawSPS;
+
+typedef struct H264RawSPSExtension {
+    H264RawNALUnitHeader nal_unit_header;
+
+    uint8_t seq_parameter_set_id;
+
+    uint8_t aux_format_idc;
+    uint8_t bit_depth_aux_minus8;
+    uint8_t alpha_incr_flag;
+    uint16_t alpha_opaque_value;
+    uint16_t alpha_transparent_value;
+
+    uint8_t additional_extension_flag;
+} H264RawSPSExtension;
+
+typedef struct H264RawPPS {
+    H264RawNALUnitHeader nal_unit_header;
+
+    uint8_t pic_parameter_set_id;
+    uint8_t seq_parameter_set_id;
+
+    uint8_t entropy_coding_mode_flag;
+    uint8_t bottom_field_pic_order_in_frame_present_flag;
+
+    uint8_t num_slice_groups_minus1;
+    uint8_t slice_group_map_type;
+    uint16_t run_length_minus1[H264_MAX_SLICE_GROUPS];
+    uint16_t top_left[H264_MAX_SLICE_GROUPS];
+    uint16_t bottom_right[H264_MAX_SLICE_GROUPS];
+    uint8_t slice_group_change_direction_flag;
+    uint16_t slice_group_change_rate_minus1;
+    uint16_t pic_size_in_map_units_minus1;
+    uint8_t slice_group_id[H264_MAX_MB_PIC_SIZE];
+
+    uint8_t num_ref_idx_l0_default_active_minus1;
+    uint8_t num_ref_idx_l1_default_active_minus1;
+
+    uint8_t weighted_pred_flag;
+    uint8_t weighted_bipred_idc;
+
+    int8_t pic_init_qp_minus26;
+    int8_t pic_init_qs_minus26;
+    int8_t chroma_qp_index_offset;
+
+    uint8_t deblocking_filter_control_present_flag;
+    uint8_t constrained_intra_pred_flag;
+
+    uint8_t more_rbsp_data;
+
+    uint8_t redundant_pic_cnt_present_flag;
+    uint8_t transform_8x8_mode_flag;
+
+    uint8_t pic_scaling_matrix_present_flag;
+    uint8_t pic_scaling_list_present_flag[12];
+    H264RawScalingList scaling_list_4x4[6];
+    H264RawScalingList scaling_list_8x8[6];
+
+    int8_t second_chroma_qp_index_offset;
+} H264RawPPS;
+
+typedef struct H264RawAUD {
+    H264RawNALUnitHeader nal_unit_header;
+
+    uint8_t primary_pic_type;
+} H264RawAUD;
+
+typedef struct H264RawSEIBufferingPeriod {
+    uint8_t seq_parameter_set_id;
+    struct {
+        uint32_t initial_cpb_removal_delay[H264_MAX_CPB_CNT];
+        uint32_t initial_cpb_removal_delay_offset[H264_MAX_CPB_CNT];
+    } nal, vcl;
+} H264RawSEIBufferingPeriod;
+
+typedef struct H264RawSEIPicTimestamp {
+    uint8_t ct_type;
+    uint8_t nuit_field_based_flag;
+    uint8_t counting_type;
+    uint8_t full_timestamp_flag;
+    uint8_t discontinuity_flag;
+    uint8_t cnt_dropped_flag;
+    uint8_t n_frames;
+    uint8_t seconds_flag;
+    uint8_t seconds_value;
+    uint8_t minutes_flag;
+    uint8_t minutes_value;
+    uint8_t hours_flag;
+    uint8_t hours_value;
+    uint32_t time_offset;
+} H264RawSEIPicTimestamp;
+
+typedef struct H264RawSEIPicTiming {
+    uint32_t cpb_removal_delay;
+    uint32_t dpb_output_delay;
+    uint8_t pic_struct;
+    uint8_t clock_timestamp_flag[3];
+    H264RawSEIPicTimestamp timestamp[3];
+} H264RawSEIPicTiming;
+
+typedef struct H264RawSEIUserDataRegistered {
+    uint8_t itu_t_t35_country_code;
+    uint8_t itu_t_t35_country_code_extension_byte;
+    uint8_t *data;
+    size_t data_length;
+} H264RawSEIUserDataRegistered;
+
+typedef struct H264RawSEIUserDataUnregistered {
+    uint8_t uuid_iso_iec_11578[16];
+    uint8_t *data;
+    size_t data_length;
+} H264RawSEIUserDataUnregistered;
+
+typedef struct H264RawSEIRecoveryPoint {
+    uint16_t recovery_frame_cnt;
+    uint8_t exact_match_flag;
+    uint8_t broken_link_flag;
+    uint8_t changing_slice_group_idc;
+} H264RawSEIRecoveryPoint;
+
+typedef struct H264RawSEIDisplayOrientation {
+    uint8_t display_orientation_cancel_flag;
+    uint8_t hor_flip;
+    uint8_t ver_flip;
+    uint16_t anticlockwise_rotation;
+    uint16_t display_orientation_repetition_period;
+    uint8_t display_orientation_extension_flag;
+} H264RawSEIDisplayOrientation;
+
+typedef struct H264RawSEIPayload {
+    uint32_t payload_type;
+    uint32_t payload_size;
+    union {
+        H264RawSEIBufferingPeriod buffering_period;
+        H264RawSEIPicTiming pic_timing;
+        // H264RawSEIFiller filler -> no fields.
+        H264RawSEIUserDataRegistered user_data_registered;
+        H264RawSEIUserDataUnregistered user_data_unregistered;
+        H264RawSEIRecoveryPoint recovery_point;
+        H264RawSEIDisplayOrientation display_orientation;
+        struct {
+            uint8_t *data;
+            size_t data_length;
+        } other;
+    } payload;
+} H264RawSEIPayload;
+
+typedef struct H264RawSEI {
+    H264RawNALUnitHeader nal_unit_header;
+
+    H264RawSEIPayload payload[H264_MAX_SEI_PAYLOADS];
+    uint8_t payload_count;
+} H264RawSEI;
+
+typedef struct H264RawSliceHeader {
+    H264RawNALUnitHeader nal_unit_header;
+
+    uint32_t first_mb_in_slice;
+    uint8_t slice_type;
+
+    uint8_t pic_parameter_set_id;
+
+    uint8_t colour_plane_id;
+
+    uint16_t frame_num;
+    uint8_t field_pic_flag;
+    uint8_t bottom_field_flag;
+
+    uint16_t idr_pic_id;
+
+    uint16_t pic_order_cnt_lsb;
+    int32_t delta_pic_order_cnt_bottom;
+    int32_t delta_pic_order_cnt[2];
+
+    uint8_t redundant_pic_cnt;
+    uint8_t direct_spatial_mv_pred_flag;
+
+    uint8_t num_ref_idx_active_override_flag;
+    uint8_t num_ref_idx_l0_active_minus1;
+    uint8_t num_ref_idx_l1_active_minus1;
+
+    uint8_t ref_pic_list_modification_flag_l0;
+    uint8_t ref_pic_list_modification_flag_l1;
+    struct {
+        uint8_t modification_of_pic_nums_idc;
+        int32_t abs_diff_pic_num_minus1;
+        uint8_t long_term_pic_num;
+    } rplm_l0[H264_MAX_RPLM_COUNT], rplm_l1[H264_MAX_RPLM_COUNT];
+
+    uint8_t luma_log2_weight_denom;
+    uint8_t chroma_log2_weight_denom;
+
+    uint8_t luma_weight_l0_flag[H264_MAX_REFS];
+    int8_t luma_weight_l0[H264_MAX_REFS];
+    int8_t luma_offset_l0[H264_MAX_REFS];
+    uint8_t chroma_weight_l0_flag[H264_MAX_REFS];
+    int8_t chroma_weight_l0[H264_MAX_REFS][2];
+    int8_t chroma_offset_l0[H264_MAX_REFS][2];
+
+    uint8_t luma_weight_l1_flag[H264_MAX_REFS];
+    int8_t luma_weight_l1[H264_MAX_REFS];
+    int8_t luma_offset_l1[H264_MAX_REFS];
+    uint8_t chroma_weight_l1_flag[H264_MAX_REFS];
+    int8_t chroma_weight_l1[H264_MAX_REFS][2];
+    int8_t chroma_offset_l1[H264_MAX_REFS][2];
+
+    uint8_t no_output_of_prior_pics_flag;
+    uint8_t long_term_reference_flag;
+
+    uint8_t adaptive_ref_pic_marking_mode_flag;
+    struct {
+        uint8_t memory_management_control_operation;
+        int32_t difference_of_pic_nums_minus1;
+        uint8_t long_term_pic_num;
+        uint8_t long_term_frame_idx;
+        uint8_t max_long_term_frame_idx_plus1;
+    } mmco[H264_MAX_MMCO_COUNT];
+
+    uint8_t cabac_init_idc;
+
+    int8_t slice_qp_delta;
+
+    uint8_t sp_for_switch_flag;
+    int8_t slice_qs_delta;
+
+    uint8_t disable_deblocking_filter_idc;
+    int8_t slice_alpha_c0_offset_div2;
+    int8_t slice_beta_offset_div2;
+
+    uint16_t slice_group_change_cycle;
+} H264RawSliceHeader;
+
+typedef struct H264RawSlice {
+    H264RawSliceHeader header;
+
+    uint8_t *data;
+    size_t   data_size;
+    int      data_bit_start;
+} H264RawSlice;
+
+
+typedef struct CodedBitstreamH264Context {
+    // Reader/writer context in common with the H.265 implementation.
+    CodedBitstreamH2645Context common;
+
+    // All currently available parameter sets.  These are updated when
+    // any parameter set NAL unit is read/written with this context.
+    H264RawSPS *sps[H264_MAX_SPS_COUNT];
+    H264RawPPS *pps[H264_MAX_PPS_COUNT];
+
+    // The currently active parameter sets.  These are updated when any
+    // NAL unit refers to the relevant parameter set.  These pointers
+    // must also be present in the arrays above.
+    const H264RawSPS *active_sps;
+    const H264RawPPS *active_pps;
+
+    // The NAL unit type of the most recent normal slice.  This is required
+    // to be able to read/write auxiliary slices, because IdrPicFlag is
+    // otherwise unknown.
+    uint8_t last_slice_nal_unit_type;
+} CodedBitstreamH264Context;
+
+
+#endif /* AVCODEC_CBS_H264_H */
diff --git a/libavcodec/cbs_h2645.c b/libavcodec/cbs_h2645.c
new file mode 100644
index 0000000000..f03fd3ce72
--- /dev/null
+++ b/libavcodec/cbs_h2645.c
@@ -0,0 +1,1010 @@
+/*
+ * 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/attributes.h"
+#include "libavutil/avassert.h"
+
+#include "bytestream.h"
+#include "cbs.h"
+#include "cbs_internal.h"
+#include "cbs_h264.h"
+#include "golomb.h"
+#include "h264.h"
+#include "h264_sei.h"
+#include "h2645_parse.h"
+
+
+static int cbs_read_ue_golomb(CodedBitstreamContext *ctx, GetBitContext *gbc,
+                              const char *name, uint32_t *write_to,
+                              uint32_t range_min, uint32_t range_max)
+{
+    uint32_t value;
+    int position, i, j;
+    unsigned int k;
+    char bits[65];
+
+    position = get_bits_count(gbc);
+
+    for (i = 0; i < 32; i++) {
+        if (get_bits_left(gbc) < i + 1) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid ue-golomb code at "
+                   "%s: bitstream ended.\n", name);
+            return AVERROR_INVALIDDATA;
+        }
+        k = get_bits1(gbc);
+        bits[i] = k ? '1' : '0';
+        if (k)
+            break;
+    }
+    if (i >= 32) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid ue-golomb code at "
+               "%s: more than 31 zeroes.\n", name);
+        return AVERROR_INVALIDDATA;
+    }
+    value = 1;
+    for (j = 0; j < i; j++) {
+        k = get_bits1(gbc);
+        bits[i + j + 1] = k ? '1' : '0';
+        value = value << 1 | k;
+    }
+    bits[i + j + 1] = 0;
+    --value;
+
+    if (ctx->trace_enable)
+        ff_cbs_trace_syntax_element(ctx, position, name, 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_read_se_golomb(CodedBitstreamContext *ctx, GetBitContext *gbc,
+                              const char *name, int32_t *write_to,
+                              int32_t range_min, int32_t range_max)
+{
+    int32_t value;
+    int position, i, j;
+    unsigned int k;
+    uint32_t v;
+    char bits[65];
+
+    position = get_bits_count(gbc);
+
+    for (i = 0; i < 32; i++) {
+        if (get_bits_left(gbc) < i + 1) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid se-golomb code at "
+                   "%s: bitstream ended.\n", name);
+            return AVERROR_INVALIDDATA;
+        }
+        k = get_bits1(gbc);
+        bits[i] = k ? '1' : '0';
+        if (k)
+            break;
+    }
+    if (i >= 32) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid se-golomb code at "
+               "%s: more than 31 zeroes.\n", name);
+        return AVERROR_INVALIDDATA;
+    }
+    v = 1;
+    for (j = 0; j < i; j++) {
+        k = get_bits1(gbc);
+        bits[i + j + 1] = k ? '1' : '0';
+        v = v << 1 | k;
+    }
+    bits[i + j + 1] = 0;
+    if (v & 1)
+        value = -(int32_t)(v / 2);
+    else
+        value = v / 2;
+
+    if (ctx->trace_enable)
+        ff_cbs_trace_syntax_element(ctx, position, name, bits, value);
+
+    if (value < range_min || value > range_max) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "%s out of range: "
+               "%"PRId32", but must be in [%"PRId32",%"PRId32"].\n",
+               name, value, range_min, range_max);
+        return AVERROR_INVALIDDATA;
+    }
+
+    *write_to = value;
+    return 0;
+}
+
+static int cbs_write_ue_golomb(CodedBitstreamContext *ctx, PutBitContext *pbc,
+                               const char *name, uint32_t value,
+                               uint32_t range_min, uint32_t range_max)
+{
+    int len;
+
+    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;
+    }
+    av_assert0(value != UINT32_MAX);
+
+    len = av_log2(value + 1);
+    if (put_bits_left(pbc) < 2 * len + 1)
+        return AVERROR(ENOSPC);
+
+    if (ctx->trace_enable) {
+        char bits[65];
+        int i;
+
+        for (i = 0; i < len; i++)
+            bits[i] = '0';
+        bits[len] = '1';
+        for (i = 0; i < len; i++)
+            bits[len + i + 1] = (value + 1) >> (len - i - 1) & 1 ? '1' : '0';
+        bits[len + len + 1] = 0;
+
+        ff_cbs_trace_syntax_element(ctx, put_bits_count(pbc), name, bits, value);
+    }
+
+    put_bits(pbc, len, 0);
+    if (len + 1 < 32)
+        put_bits(pbc, len + 1, value + 1);
+    else
+        put_bits32(pbc, value + 1);
+
+    return 0;
+}
+
+static int cbs_write_se_golomb(CodedBitstreamContext *ctx, PutBitContext *pbc,
+                               const char *name, int32_t value,
+                               int32_t range_min, int32_t range_max)
+{
+    int len;
+    uint32_t uvalue;
+
+    if (value < range_min || value > range_max) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "%s out of range: "
+               "%"PRId32", but must be in [%"PRId32",%"PRId32"].\n",
+               name, value, range_min, range_max);
+        return AVERROR_INVALIDDATA;
+    }
+    av_assert0(value != INT32_MIN);
+
+    if (value == 0)
+        uvalue = 0;
+    else if (value > 0)
+        uvalue = 2 * (uint32_t)value - 1;
+    else
+        uvalue = 2 * (uint32_t)-value;
+
+    len = av_log2(uvalue + 1);
+    if (put_bits_left(pbc) < 2 * len + 1)
+        return AVERROR(ENOSPC);
+
+    if (ctx->trace_enable) {
+        char bits[65];
+        int i;
+
+        for (i = 0; i < len; i++)
+            bits[i] = '0';
+        bits[len] = '1';
+        for (i = 0; i < len; i++)
+            bits[len + i + 1] = (uvalue + 1) >> (len - i - 1) & 1 ? '1' : '0';
+        bits[len + len + 1] = 0;
+
+        ff_cbs_trace_syntax_element(ctx, put_bits_count(pbc), name, bits, value);
+    }
+
+    put_bits(pbc, len, 0);
+    if (len + 1 < 32)
+        put_bits(pbc, len + 1, uvalue + 1);
+    else
+        put_bits32(pbc, uvalue + 1);
+
+    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_H264(rw, name) FUNC_NAME(rw, h264, name)
+
+
+#define READ
+#define READWRITE read
+#define RWContext GetBitContext
+
+#define xu(width, name, var, range_min, range_max) do { \
+        uint32_t value = range_min; \
+        CHECK(ff_cbs_read_unsigned(ctx, rw, width, #name, \
+                                   &value, range_min, range_max)); \
+        var = value; \
+    } while (0)
+#define xue(name, var, range_min, range_max) do { \
+        uint32_t value = range_min; \
+        CHECK(cbs_read_ue_golomb(ctx, rw, #name, \
+                                 &value, range_min, range_max)); \
+        var = value; \
+    } while (0)
+#define xse(name, var, range_min, range_max) do { \
+        int32_t value = range_min; \
+        CHECK(cbs_read_se_golomb(ctx, rw, #name, \
+                                 &value, range_min, range_max)); \
+        var = value; \
+    } while (0)
+
+
+#define u(width, name, range_min, range_max) \
+        xu(width, name, current->name, range_min, range_max)
+#define flag(name) u(1, name, 0, 1)
+#define ue(name, range_min, range_max) \
+        xue(name, current->name, range_min, range_max)
+#define se(name, range_min, range_max) \
+        xse(name, current->name, range_min, range_max)
+
+#define infer(name, value) do { \
+        current->name = value; \
+    } while (0)
+
+static int cbs_h2645_read_more_rbsp_data(GetBitContext *gbc)
+{
+    int bits_left = get_bits_left(gbc);
+    if (bits_left > 8)
+        return 1;
+    if (show_bits(gbc, bits_left) == 1 << (bits_left - 1))
+        return 0;
+    return 1;
+}
+
+#define more_rbsp_data(var) ((var) = cbs_h2645_read_more_rbsp_data(rw))
+
+#define byte_alignment(rw) (get_bits_count(rw) % 8)
+
+#define allocate(name, size) do { \
+        name = av_mallocz(size); \
+        if (!name) \
+            return AVERROR(ENOMEM); \
+    } while (0)
+
+#define FUNC(name) FUNC_H264(READWRITE, name)
+#include "cbs_h264_syntax_template.c"
+#undef FUNC
+
+#undef READ
+#undef READWRITE
+#undef RWContext
+#undef xu
+#undef xue
+#undef xse
+#undef u
+#undef flag
+#undef ue
+#undef se
+#undef infer
+#undef more_rbsp_data
+#undef byte_alignment
+#undef allocate
+
+
+#define WRITE
+#define READWRITE write
+#define RWContext PutBitContext
+
+#define xu(width, name, var, range_min, range_max) do { \
+        uint32_t value = var; \
+        CHECK(ff_cbs_write_unsigned(ctx, rw, width, #name, \
+                                    value, range_min, range_max)); \
+    } while (0)
+#define xue(name, var, range_min, range_max) do { \
+        uint32_t value = var; \
+        CHECK(cbs_write_ue_golomb(ctx, rw, #name, \
+                                  value, range_min, range_max)); \
+    } while (0)
+#define xse(name, var, range_min, range_max) do { \
+        int32_t value = var; \
+        CHECK(cbs_write_se_golomb(ctx, rw, #name, \
+                                  value, range_min, range_max)); \
+    } while (0)
+
+#define u(width, name, range_min, range_max) \
+        xu(width, name, current->name, range_min, range_max)
+#define flag(name) u(1, name, 0, 1)
+#define ue(name, range_min, range_max) \
+        xue(name, current->name, range_min, range_max)
+#define se(name, range_min, range_max) \
+        xse(name, current->name, range_min, range_max)
+
+#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 more_rbsp_data(var) (var)
+
+#define byte_alignment(rw) (put_bits_count(rw) % 8)
+
+#define allocate(name, size) do { \
+        if (!name) { \
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "%s must be set " \
+                   "for writing.\n", #name); \
+            return AVERROR_INVALIDDATA; \
+        } \
+    } while (0)
+
+#define FUNC(name) FUNC_H264(READWRITE, name)
+#include "cbs_h264_syntax_template.c"
+#undef FUNC
+
+#undef WRITE
+#undef READWRITE
+#undef RWContext
+#undef xu
+#undef xue
+#undef xse
+#undef u
+#undef flag
+#undef ue
+#undef se
+#undef infer
+#undef more_rbsp_data
+#undef byte_alignment
+#undef allocate
+
+
+static void cbs_h264_free_sei(H264RawSEI *sei)
+{
+    int i;
+    for (i = 0; i < sei->payload_count; i++) {
+        H264RawSEIPayload *payload = &sei->payload[i];
+
+        switch (payload->payload_type) {
+        case H264_SEI_TYPE_BUFFERING_PERIOD:
+        case H264_SEI_TYPE_PIC_TIMING:
+        case H264_SEI_TYPE_RECOVERY_POINT:
+        case H264_SEI_TYPE_DISPLAY_ORIENTATION:
+            break;
+        case H264_SEI_TYPE_USER_DATA_REGISTERED:
+            av_freep(&payload->payload.user_data_registered.data);
+            break;
+        case H264_SEI_TYPE_USER_DATA_UNREGISTERED:
+            av_freep(&payload->payload.user_data_unregistered.data);
+            break;
+        default:
+            av_freep(&payload->payload.other.data);
+            break;
+        }
+    }
+}
+
+static void cbs_h264_free_slice(H264RawSlice *slice)
+{
+    av_freep(&slice->data);
+}
+
+static void cbs_h264_free_nal_unit(CodedBitstreamUnit *unit)
+{
+    switch (unit->type) {
+    case H264_NAL_SEI:
+        cbs_h264_free_sei(unit->content);
+        break;
+    case H264_NAL_IDR_SLICE:
+    case H264_NAL_SLICE:
+        cbs_h264_free_slice(unit->content);
+        break;
+    }
+    av_freep(&unit->content);
+}
+
+static int cbs_h2645_fragment_add_nals(CodedBitstreamContext *ctx,
+                                       CodedBitstreamFragment *frag,
+                                       const H2645Packet *packet)
+{
+    int err, i;
+
+    for (i = 0; i < packet->nb_nals; i++) {
+        const H2645NAL *nal = &packet->nals[i];
+        size_t size = nal->size;
+        uint8_t *data;
+
+        // Remove trailing zeroes.
+        while (size > 0 && nal->data[size - 1] == 0)
+            --size;
+        av_assert0(size > 0);
+
+        data = av_malloc(size + AV_INPUT_BUFFER_PADDING_SIZE);
+        if (!data)
+            return AVERROR(ENOMEM);
+        memcpy(data, nal->data, size);
+        memset(data + size, 0, AV_INPUT_BUFFER_PADDING_SIZE);
+
+        err = ff_cbs_insert_unit_data(ctx, frag, -1, nal->type,
+                                      data, size);
+        if (err < 0) {
+            av_freep(&data);
+            return err;
+        }
+    }
+
+    return 0;
+}
+
+static int cbs_h2645_split_fragment(CodedBitstreamContext *ctx,
+                                    CodedBitstreamFragment *frag,
+                                    int header)
+{
+    enum AVCodecID codec_id = ctx->codec->codec_id;
+    CodedBitstreamH2645Context *priv = ctx->priv_data;
+    GetByteContext gbc;
+    int err;
+
+    av_assert0(frag->data && frag->nb_units == 0);
+    if (frag->data_size == 0)
+        return 0;
+
+    if (header && frag->data[0] && codec_id == AV_CODEC_ID_H264) {
+        // AVCC header.
+        size_t size, start, end;
+        int i, count, version;
+
+        priv->mp4 = 1;
+
+        bytestream2_init(&gbc, frag->data, frag->data_size);
+
+        if (bytestream2_get_bytes_left(&gbc) < 6)
+            return AVERROR_INVALIDDATA;
+
+        version = bytestream2_get_byte(&gbc);
+        if (version != 1) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid AVCC header: "
+                   "first byte %u.", version);
+            return AVERROR_INVALIDDATA;
+        }
+
+        bytestream2_skip(&gbc, 3);
+        priv->nal_length_size = (bytestream2_get_byte(&gbc) & 3) + 1;
+
+        // SPS array.
+        count = bytestream2_get_byte(&gbc) & 0x1f;
+        start = bytestream2_tell(&gbc);
+        for (i = 0; i < count; i++) {
+            if (bytestream2_get_bytes_left(&gbc) < 2 * (count - i))
+                return AVERROR_INVALIDDATA;
+            size = bytestream2_get_be16(&gbc);
+            if (bytestream2_get_bytes_left(&gbc) < size)
+                return AVERROR_INVALIDDATA;
+            bytestream2_skip(&gbc, size);
+        }
+        end = bytestream2_tell(&gbc);
+
+        err = ff_h2645_packet_split(&priv->read_packet,
+                                    frag->data + start, end - start,
+                                    ctx->log_ctx, 1, 2, AV_CODEC_ID_H264, 1);
+        if (err < 0) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Failed to split AVCC SPS array.\n");
+            return err;
+        }
+        err = cbs_h2645_fragment_add_nals(ctx, frag, &priv->read_packet);
+        if (err < 0)
+            return err;
+
+        // PPS array.
+        count = bytestream2_get_byte(&gbc);
+        start = bytestream2_tell(&gbc);
+        for (i = 0; i < count; i++) {
+            if (bytestream2_get_bytes_left(&gbc) < 2 * (count - i))
+                return AVERROR_INVALIDDATA;
+            size = bytestream2_get_be16(&gbc);
+            if (bytestream2_get_bytes_left(&gbc) < size)
+                return AVERROR_INVALIDDATA;
+            bytestream2_skip(&gbc, size);
+        }
+        end = bytestream2_tell(&gbc);
+
+        err = ff_h2645_packet_split(&priv->read_packet,
+                                    frag->data + start, end - start,
+                                    ctx->log_ctx, 1, 2, AV_CODEC_ID_H264, 1);
+        if (err < 0) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Failed to split AVCC PPS array.\n");
+            return err;
+        }
+        err = cbs_h2645_fragment_add_nals(ctx, frag, &priv->read_packet);
+        if (err < 0)
+            return err;
+
+        if (bytestream2_get_bytes_left(&gbc) > 0) {
+            av_log(ctx->log_ctx, AV_LOG_WARNING, "%u bytes left at end of AVCC "
+                   "header.\n", bytestream2_get_bytes_left(&gbc));
+        }
+
+    } else {
+        // Annex B, or later MP4 with already-known parameters.
+
+        err = ff_h2645_packet_split(&priv->read_packet,
+                                    frag->data, frag->data_size,
+                                    ctx->log_ctx,
+                                    priv->mp4, priv->nal_length_size,
+                                    codec_id, 1);
+        if (err < 0)
+            return err;
+
+        err = cbs_h2645_fragment_add_nals(ctx, frag, &priv->read_packet);
+        if (err < 0)
+            return err;
+    }
+
+    return 0;
+}
+
+#define cbs_h2645_replace_ps(h26n, ps_name, ps_var, id_element) \
+static int cbs_h26 ## h26n ## _replace_ ## ps_var(CodedBitstreamContext *ctx, \
+                                                  const H26 ## h26n ## Raw ## ps_name *ps_var)  \
+{ \
+    CodedBitstreamH26 ## h26n ## Context *priv = ctx->priv_data; \
+    unsigned int id = ps_var->id_element; \
+    if (id > FF_ARRAY_ELEMS(priv->ps_var)) { \
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid " #ps_name \
+               " id : %d.\n", id); \
+        return AVERROR_INVALIDDATA; \
+    } \
+    av_freep(&priv->ps_var[id]); \
+    priv->ps_var[id] = av_malloc(sizeof(*ps_var)); \
+    if (!priv->ps_var[id]) \
+        return AVERROR(ENOMEM); \
+    memcpy(priv->ps_var[id], ps_var, sizeof(*ps_var)); \
+    return 0; \
+}
+
+cbs_h2645_replace_ps(4, SPS, sps, seq_parameter_set_id)
+cbs_h2645_replace_ps(4, PPS, pps, pic_parameter_set_id)
+
+static int cbs_h264_read_nal_unit(CodedBitstreamContext *ctx,
+                                  CodedBitstreamUnit *unit)
+{
+    GetBitContext gbc;
+    int err;
+
+    err = init_get_bits(&gbc, unit->data, 8 * unit->data_size);
+    if (err < 0)
+        return err;
+
+    switch (unit->type) {
+    case H264_NAL_SPS:
+        {
+            H264RawSPS *sps;
+
+            sps = av_mallocz(sizeof(*sps));
+            if (!sps)
+                return AVERROR(ENOMEM);
+            err = cbs_h264_read_sps(ctx, &gbc, sps);
+            if (err >= 0)
+                err = cbs_h264_replace_sps(ctx, sps);
+            if (err < 0) {
+                av_free(sps);
+                return err;
+            }
+
+            unit->content = sps;
+        }
+        break;
+
+    case H264_NAL_SPS_EXT:
+        {
+            H264RawSPSExtension *sps_ext;
+
+            sps_ext = av_mallocz(sizeof(*sps_ext));
+            if (!sps_ext)
+                return AVERROR(ENOMEM);
+            err = cbs_h264_read_sps_extension(ctx, &gbc, sps_ext);
+            if (err < 0) {
+                av_free(sps_ext);
+                return err;
+            }
+
+            unit->content = sps_ext;
+        }
+        break;
+
+    case H264_NAL_PPS:
+        {
+            H264RawPPS *pps;
+
+            pps = av_mallocz(sizeof(*pps));
+            if (!pps)
+                return AVERROR(ENOMEM);
+            err = cbs_h264_read_pps(ctx, &gbc, pps);
+            if (err >= 0)
+                err = cbs_h264_replace_pps(ctx, pps);
+            if (err < 0) {
+                av_free(pps);
+                return err;
+            }
+
+            unit->content = pps;
+        }
+        break;
+
+    case H264_NAL_SLICE:
+    case H264_NAL_IDR_SLICE:
+    case H264_NAL_AUXILIARY_SLICE:
+        {
+            H264RawSlice *slice;
+            int pos, len;
+
+            slice = av_mallocz(sizeof(*slice));
+            if (!slice)
+                return AVERROR(ENOMEM);
+            err = cbs_h264_read_slice_header(ctx, &gbc, &slice->header);
+            if (err < 0) {
+                av_free(slice);
+                return err;
+            }
+
+            pos = get_bits_count(&gbc);
+            len = unit->data_size;
+            if (!unit->data[len - 1]) {
+                int z;
+                for (z = 0; z < len && !unit->data[len - z - 1]; z++);
+                av_log(ctx->log_ctx, AV_LOG_DEBUG, "Deleted %d trailing zeroes "
+                       "from slice data.\n", z);
+                len -= z;
+            }
+
+            slice->data_size = len - pos / 8;
+            slice->data = av_malloc(slice->data_size +
+                                    AV_INPUT_BUFFER_PADDING_SIZE);
+            if (!slice->data) {
+                av_free(slice);
+                return AVERROR(ENOMEM);
+            }
+            memcpy(slice->data,
+                   unit->data + pos / 8, slice->data_size);
+            memset(slice->data + slice->data_size, 0,
+                   AV_INPUT_BUFFER_PADDING_SIZE);
+            slice->data_bit_start = pos % 8;
+
+            unit->content = slice;
+        }
+        break;
+
+    case H264_NAL_AUD:
+        {
+            H264RawAUD *aud;
+
+            aud = av_mallocz(sizeof(*aud));
+            if (!aud)
+                return AVERROR(ENOMEM);
+            err = cbs_h264_read_aud(ctx, &gbc, aud);
+            if (err < 0) {
+                av_free(aud);
+                return err;
+            }
+
+            unit->content = aud;
+        }
+        break;
+
+    case H264_NAL_SEI:
+        {
+            H264RawSEI *sei;
+
+            sei = av_mallocz(sizeof(*sei));
+            if (!sei)
+                return AVERROR(ENOMEM);
+            err = cbs_h264_read_sei(ctx, &gbc, sei);
+            if (err < 0) {
+                cbs_h264_free_sei(sei);
+                return err;
+            }
+
+            unit->content = sei;
+        }
+        break;
+
+    default:
+        return AVERROR(ENOSYS);
+    }
+
+    return 0;
+}
+
+static int cbs_h264_write_nal_unit(CodedBitstreamContext *ctx,
+                                   CodedBitstreamUnit *unit,
+                                   PutBitContext *pbc)
+{
+    int err;
+
+    switch (unit->type) {
+    case H264_NAL_SPS:
+        {
+            H264RawSPS *sps = unit->content;
+
+            err = cbs_h264_write_sps(ctx, pbc, sps);
+            if (err < 0)
+                return err;
+
+            err = cbs_h264_replace_sps(ctx, sps);
+            if (err < 0)
+                return err;
+        }
+        break;
+
+    case H264_NAL_SPS_EXT:
+        {
+            H264RawSPSExtension *sps_ext;
+
+            err = cbs_h264_write_sps_extension(ctx, pbc, sps_ext);
+            if (err < 0)
+                return err;
+        }
+        break;
+
+    case H264_NAL_PPS:
+        {
+            H264RawPPS *pps = unit->content;
+
+            err = cbs_h264_write_pps(ctx, pbc, pps);
+            if (err < 0)
+                return err;
+
+            err = cbs_h264_replace_pps(ctx, pps);
+            if (err < 0)
+                return err;
+        }
+        break;
+
+    case H264_NAL_SLICE:
+    case H264_NAL_IDR_SLICE:
+        {
+            H264RawSlice *slice = unit->content;
+            GetBitContext gbc;
+            int bits_left, end, zeroes;
+
+            err = cbs_h264_write_slice_header(ctx, pbc, &slice->header);
+            if (err < 0)
+                return err;
+
+            if (slice->data) {
+                if (slice->data_size * 8 + 8 > put_bits_left(pbc))
+                    return AVERROR(ENOSPC);
+
+                init_get_bits(&gbc, slice->data, slice->data_size * 8);
+                skip_bits_long(&gbc, slice->data_bit_start);
+
+                // Copy in two-byte blocks, but stop before copying the
+                // rbsp_stop_one_bit in the final byte.
+                while (get_bits_left(&gbc) > 23)
+                    put_bits(pbc, 16, get_bits(&gbc, 16));
+
+                bits_left = get_bits_left(&gbc);
+                end = get_bits(&gbc, bits_left);
+
+                // rbsp_stop_one_bit must be present here.
+                av_assert0(end);
+                zeroes = ff_ctz(end);
+                if (bits_left > zeroes + 1)
+                    put_bits(pbc, bits_left - zeroes - 1,
+                             end >> (zeroes + 1));
+                put_bits(pbc, 1, 1);
+                while (put_bits_count(pbc) % 8 != 0)
+                    put_bits(pbc, 1, 0);
+            } else {
+                // No slice data - that was just the header.
+                // (Bitstream may be unaligned!)
+            }
+        }
+        break;
+
+    case H264_NAL_AUD:
+        {
+            err = cbs_h264_write_aud(ctx, pbc, unit->content);
+            if (err < 0)
+                return err;
+        }
+        break;
+
+    case H264_NAL_SEI:
+        {
+            err = cbs_h264_write_sei(ctx, pbc, unit->content);
+            if (err < 0)
+                return err;
+        }
+        break;
+
+    default:
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Write unimplemented for "
+               "NAL unit type %"PRIu32".\n", unit->type);
+        return AVERROR_PATCHWELCOME;
+    }
+
+    return 0;
+}
+
+static int cbs_h2645_write_nal_unit(CodedBitstreamContext *ctx,
+                                    CodedBitstreamUnit *unit)
+{
+    CodedBitstreamH2645Context *priv = ctx->priv_data;
+    enum AVCodecID codec_id = ctx->codec->codec_id;
+    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_h264_write_nal_unit(ctx, unit, &pbc);
+
+    if (err == AVERROR(ENOSPC)) {
+        // Overflow.
+        priv->write_buffer_size *= 2;
+        goto reallocate_and_try_again;
+    }
+    // Overflow but we didn't notice.
+    av_assert0(put_bits_count(&pbc) <= 8 * priv->write_buffer_size);
+
+    if (err < 0) {
+        // Write failed for some other reason.
+        return err;
+    }
+
+    if (put_bits_count(&pbc) % 8)
+        unit->data_bit_padding = 8 - put_bits_count(&pbc) % 8;
+    else
+        unit->data_bit_padding = 0;
+
+    unit->data_size = (put_bits_count(&pbc) + 7) / 8;
+    flush_put_bits(&pbc);
+
+    err = av_reallocp(&unit->data, unit->data_size);
+    if (err < 0)
+        return err;
+
+    memcpy(unit->data, priv->write_buffer, unit->data_size);
+
+    return 0;
+}
+
+static int cbs_h2645_assemble_fragment(CodedBitstreamContext *ctx,
+                                       CodedBitstreamFragment *frag)
+{
+    uint8_t *data;
+    size_t max_size, dp, sp;
+    int err, i, zero_run;
+
+    for (i = 0; i < frag->nb_units; i++) {
+        // Data should already all have been written when we get here.
+        av_assert0(frag->units[i].data);
+    }
+
+    max_size = 0;
+    for (i = 0; i < frag->nb_units; i++) {
+        // Start code + content with worst-case emulation prevention.
+        max_size += 3 + frag->units[i].data_size * 3 / 2;
+    }
+
+    data = av_malloc(max_size);
+    if (!data)
+        return AVERROR(ENOMEM);
+
+    dp = 0;
+    for (i = 0; i < frag->nb_units; i++) {
+        CodedBitstreamUnit *unit = &frag->units[i];
+
+        if (unit->data_bit_padding > 0) {
+            if (i < frag->nb_units - 1)
+                av_log(ctx->log_ctx, AV_LOG_WARNING, "Probably invalid "
+                       "unaligned padding on non-final NAL unit.\n");
+            else
+                frag->data_bit_padding = unit->data_bit_padding;
+        }
+
+        if (unit->type == H264_NAL_SPS ||
+            unit->type == H264_NAL_PPS ||
+            i == 0 /* (Assume this is the start of an access unit.) */) {
+            // zero_byte
+            data[dp++] = 0;
+        }
+        // start_code_prefix_one_3bytes
+        data[dp++] = 0;
+        data[dp++] = 0;
+        data[dp++] = 1;
+
+        zero_run = 0;
+        for (sp = 0; sp < unit->data_size; sp++) {
+            if (zero_run < 2) {
+                if (unit->data[sp] == 0)
+                    ++zero_run;
+                else
+                    zero_run = 0;
+            } else {
+                if ((unit->data[sp] & ~3) == 0) {
+                    // emulation_prevention_three_byte
+                    data[dp++] = 3;
+                }
+                zero_run = unit->data[sp] == 0;
+            }
+            data[dp++] = unit->data[sp];
+        }
+    }
+
+    av_assert0(dp <= max_size);
+    err = av_reallocp(&data, dp);
+    if (err)
+        return err;
+
+    frag->data = data;
+    frag->data_size = dp;
+
+    return 0;
+}
+
+static void cbs_h264_close(CodedBitstreamContext *ctx)
+{
+    CodedBitstreamH264Context *h264 = ctx->priv_data;
+    int i;
+
+    ff_h2645_packet_uninit(&h264->common.read_packet);
+
+    av_freep(&h264->common.write_buffer);
+
+    for (i = 0; i < FF_ARRAY_ELEMS(h264->sps); i++)
+        av_freep(&h264->sps[i]);
+    for (i = 0; i < FF_ARRAY_ELEMS(h264->pps); i++)
+        av_freep(&h264->pps[i]);
+}
+
+const CodedBitstreamType ff_cbs_type_h264 = {
+    .codec_id          = AV_CODEC_ID_H264,
+
+    .priv_data_size    = sizeof(CodedBitstreamH264Context),
+
+    .split_fragment    = &cbs_h2645_split_fragment,
+    .read_unit         = &cbs_h264_read_nal_unit,
+    .write_unit        = &cbs_h2645_write_nal_unit,
+    .assemble_fragment = &cbs_h2645_assemble_fragment,
+
+    .free_unit         = &cbs_h264_free_nal_unit,
+    .close             = &cbs_h264_close,
+};
diff --git a/libavcodec/cbs_h2645.h b/libavcodec/cbs_h2645.h
new file mode 100644
index 0000000000..f4cf65bdde
--- /dev/null
+++ b/libavcodec/cbs_h2645.h
@@ -0,0 +1,43 @@
+/*
+ * 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_H2645_H
+#define AVCODEC_CBS_H2645_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "h2645_parse.h"
+
+
+typedef struct CodedBitstreamH2645Context {
+    // If set, the stream being read is in MP4 (AVCC/HVCC) format.  If not
+    // set, the stream is assumed to be in annex B format.
+    int mp4;
+    // Size in bytes of the NAL length field for MP4 format.
+    int nal_length_size;
+    // Packet reader.
+    H2645Packet read_packet;
+
+    // Write buffer
+    uint8_t *write_buffer;
+    size_t write_buffer_size;
+} CodedBitstreamH2645Context;
+
+
+#endif /* AVCODEC_CBS_H2645_H */
diff --git a/libavcodec/cbs_h264_syntax_template.c b/libavcodec/cbs_h264_syntax_template.c
new file mode 100644
index 0000000000..8303acbdc4
--- /dev/null
+++ b/libavcodec/cbs_h264_syntax_template.c
@@ -0,0 +1,1230 @@
+/*
+ * 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(rbsp_trailing_bits)(CodedBitstreamContext *ctx, RWContext *rw)
+{
+    int err;
+    av_unused int one = 1, zero = 0;
+    xu(1, rbsp_stop_one_bit, one, 1, 1);
+    while (byte_alignment(rw) != 0)
+        xu(1, rbsp_alignment_zero_bit, zero, 0, 0);
+
+    return 0;
+}
+
+static int FUNC(nal_unit_header)(CodedBitstreamContext *ctx, RWContext *rw,
+                                 H264RawNALUnitHeader *current,
+                                 uint32_t valid_type_mask)
+{
+    int err;
+
+    u(1, forbidden_zero_bit, 0, 0);
+    u(2, nal_ref_idc,        0, 3);
+    u(5, nal_unit_type,      0, 31);
+
+    if (!(1 << current->nal_unit_type & valid_type_mask)) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid NAL unit type %d.\n",
+               current->nal_unit_type);
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (current->nal_unit_type == 14 ||
+        current->nal_unit_type == 20 ||
+        current->nal_unit_type == 21) {
+        if (current->nal_unit_type != 21)
+            flag(svc_extension_flag);
+        else
+            flag(avc_3d_extension_flag);
+
+        if (current->svc_extension_flag) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "SVC not supported.\n");
+            return AVERROR_PATCHWELCOME;
+
+        } else if (current->avc_3d_extension_flag) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "3DAVC not supported.\n");
+            return AVERROR_PATCHWELCOME;
+
+        } else {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "MVC not supported.\n");
+            return AVERROR_PATCHWELCOME;
+        }
+    }
+
+    return 0;
+}
+
+static int FUNC(scaling_list)(CodedBitstreamContext *ctx, RWContext *rw,
+                              H264RawScalingList *current,
+                              int size_of_scaling_list)
+{
+    int err, i, scale;
+
+    scale = 8;
+    for (i = 0; i < size_of_scaling_list; i++) {
+        xse(delta_scale, current->delta_scale[i], -128, +127);
+        scale = (scale + current->delta_scale[i] + 256) % 256;
+        if (scale == 0)
+            break;
+    }
+
+    return 0;
+}
+
+static int FUNC(hrd_parameters)(CodedBitstreamContext *ctx, RWContext *rw,
+                                H264RawHRD *current)
+{
+    int err, i;
+
+    ue(cpb_cnt_minus1, 0, 31);
+    u(4, bit_rate_scale, 0, 15);
+    u(4, cpb_size_scale, 0, 15);
+
+    for (i = 0; i <= current->cpb_cnt_minus1; i++) {
+        ue(bit_rate_value_minus1[i], 0, UINT32_MAX - 1);
+        ue(cpb_size_value_minus1[i], 0, UINT32_MAX - 1);
+        flag(cbr_flag[i]);
+    }
+
+    u(5, initial_cpb_removal_delay_length_minus1, 0, 31);
+    u(5, cpb_removal_delay_length_minus1,         0, 31);
+    u(5, dpb_output_delay_length_minus1,          0, 31);
+    u(5, time_offset_length,                      0, 31);
+
+    return 0;
+}
+
+static int FUNC(vui_parameters)(CodedBitstreamContext *ctx, RWContext *rw,
+                                H264RawVUI *current, H264RawSPS *sps)
+{
+    int err;
+
+    flag(aspect_ratio_info_present_flag);
+    if (current->aspect_ratio_info_present_flag) {
+        u(8, aspect_ratio_idc, 0, 255);
+        if (current->aspect_ratio_idc == 255) {
+            u(16, sar_width,  0, 65535);
+            u(16, sar_height, 0, 65535);
+        }
+    } else {
+        infer(aspect_ratio_idc, 0);
+    }
+
+    flag(overscan_info_present_flag);
+    if (current->overscan_info_present_flag)
+        flag(overscan_appropriate_flag);
+
+    flag(video_signal_type_present_flag);
+    if (current->video_signal_type_present_flag) {
+        u(3, video_format, 0, 7);
+        flag(video_full_range_flag);
+        flag(colour_description_present_flag);
+        if (current->colour_description_present_flag) {
+            u(8, colour_primaries,         0, 255);
+            u(8, transfer_characteristics, 0, 255);
+            u(8, matrix_coefficients,      0, 255);
+        }
+    } else {
+        infer(video_format,             5);
+        infer(video_full_range_flag,    0);
+        infer(colour_primaries,         2);
+        infer(transfer_characteristics, 2);
+        infer(matrix_coefficients,      2);
+    }
+
+    flag(chroma_loc_info_present_flag);
+    if (current->chroma_loc_info_present_flag) {
+        ue(chroma_sample_loc_type_top_field,    0, 5);
+        ue(chroma_sample_loc_type_bottom_field, 0, 5);
+    } else {
+        infer(chroma_sample_loc_type_top_field,    0);
+        infer(chroma_sample_loc_type_bottom_field, 0);
+    }
+
+    flag(timing_info_present_flag);
+    if (current->timing_info_present_flag) {
+        u(32, num_units_in_tick, 1, UINT32_MAX);
+        u(32, time_scale,        1, UINT32_MAX);
+        flag(fixed_frame_rate_flag);
+    } else {
+        infer(fixed_frame_rate_flag, 0);
+    }
+
+    flag(nal_hrd_parameters_present_flag);
+    if (current->nal_hrd_parameters_present_flag)
+        CHECK(FUNC(hrd_parameters)(ctx, rw, &current->nal_hrd_parameters));
+
+    flag(vcl_hrd_parameters_present_flag);
+    if (current->vcl_hrd_parameters_present_flag)
+        CHECK(FUNC(hrd_parameters)(ctx, rw, &current->vcl_hrd_parameters));
+
+    if (current->nal_hrd_parameters_present_flag ||
+        current->vcl_hrd_parameters_present_flag)
+        flag(low_delay_hrd_flag);
+    else
+        infer(low_delay_hrd_flag, 1 - current->fixed_frame_rate_flag);
+
+    flag(pic_struct_present_flag);
+
+    flag(bitstream_restriction_flag);
+    if (current->bitstream_restriction_flag) {
+        flag(motion_vectors_over_pic_boundaries_flag);
+        ue(max_bytes_per_pic_denom, 0, 16);
+        ue(max_bits_per_mb_denom,   0, 16);
+        ue(log2_max_mv_length_horizontal, 0, 16);
+        ue(log2_max_mv_length_vertical,   0, 16);
+        ue(max_num_reorder_frames,  0, H264_MAX_DPB_FRAMES);
+        ue(max_dec_frame_buffering, 0, H264_MAX_DPB_FRAMES);
+    } else {
+        infer(motion_vectors_over_pic_boundaries_flag, 1);
+        infer(max_bytes_per_pic_denom, 2);
+        infer(max_bits_per_mb_denom,   1);
+        infer(log2_max_mv_length_horizontal, 16);
+        infer(log2_max_mv_length_vertical,   16);
+
+        if ((sps->profile_idc ==  44 || sps->profile_idc ==  86 ||
+             sps->profile_idc == 110 || sps->profile_idc == 110 ||
+             sps->profile_idc == 122 || sps->profile_idc == 244) &&
+            sps->constraint_set3_flag) {
+            infer(max_num_reorder_frames,  0);
+            infer(max_dec_frame_buffering, 0);
+        } else {
+            infer(max_num_reorder_frames,  H264_MAX_DPB_FRAMES);
+            infer(max_dec_frame_buffering, H264_MAX_DPB_FRAMES);
+        }
+    }
+
+    return 0;
+}
+
+static int FUNC(sps)(CodedBitstreamContext *ctx, RWContext *rw,
+                     H264RawSPS *current)
+{
+    int err, i;
+
+    HEADER("Sequence Parameter Set");
+
+    CHECK(FUNC(nal_unit_header)(ctx, rw, &current->nal_unit_header,
+                                1 << H264_NAL_SPS));
+
+    u(8, profile_idc, 0, 255);
+
+    flag(constraint_set0_flag);
+    flag(constraint_set1_flag);
+    flag(constraint_set2_flag);
+    flag(constraint_set3_flag);
+    flag(constraint_set4_flag);
+    flag(constraint_set5_flag);
+
+    u(2, reserved_zero_2bits,  0, 0);
+
+    u(8, level_idc, 0, 255);
+
+    ue(seq_parameter_set_id, 0, 31);
+
+    if (current->profile_idc == 100 || current->profile_idc == 110 ||
+        current->profile_idc == 122 || current->profile_idc == 244 ||
+        current->profile_idc ==  44 || current->profile_idc ==  83 ||
+        current->profile_idc ==  86 || current->profile_idc == 118 ||
+        current->profile_idc == 128 || current->profile_idc == 138) {
+        ue(chroma_format_idc, 0, 3);
+
+        if (current->chroma_format_idc == 3)
+            flag(separate_colour_plane_flag);
+        else
+            infer(separate_colour_plane_flag, 0);
+
+        ue(bit_depth_luma_minus8,   0, 6);
+        ue(bit_depth_chroma_minus8, 0, 6);
+
+        flag(qpprime_y_zero_transform_bypass_flag);
+
+        flag(seq_scaling_matrix_present_flag);
+        if (current->seq_scaling_matrix_present_flag) {
+            for (i = 0; i < ((current->chroma_format_idc != 3) ? 8 : 12); i++) {
+                flag(seq_scaling_list_present_flag[i]);
+                if (current->seq_scaling_list_present_flag[i]) {
+                    if (i < 6)
+                        CHECK(FUNC(scaling_list)(ctx, rw,
+                                                 &current->scaling_list_4x4[i],
+                                                 16));
+                    else
+                        CHECK(FUNC(scaling_list)(ctx, rw,
+                                                 &current->scaling_list_8x8[i - 6],
+                                                 64));
+                }
+            }
+        }
+    } else {
+        infer(chroma_format_idc, current->profile_idc == 183 ? 0 : 1);
+
+        infer(separate_colour_plane_flag, 0);
+        infer(bit_depth_luma_minus8,      0);
+        infer(bit_depth_chroma_minus8,    0);
+    }
+
+    ue(log2_max_frame_num_minus4, 0, 12);
+    ue(pic_order_cnt_type, 0, 2);
+
+    if (current->pic_order_cnt_type == 0) {
+        ue(log2_max_pic_order_cnt_lsb_minus4, 0, 12);
+    } else if (current->pic_order_cnt_type == 1) {
+        flag(delta_pic_order_always_zero_flag);
+        se(offset_for_non_ref_pic,         INT32_MIN + 1, INT32_MAX);
+        se(offset_for_top_to_bottom_field, INT32_MIN + 1, INT32_MAX);
+        ue(num_ref_frames_in_pic_order_cnt_cycle, 0, 255);
+
+        for (i = 0; i < current->num_ref_frames_in_pic_order_cnt_cycle; i++)
+            se(offset_for_ref_frame[i], INT32_MIN + 1, INT32_MAX);
+    }
+
+    ue(max_num_ref_frames, 0, H264_MAX_DPB_FRAMES);
+    flag(gaps_in_frame_num_allowed_flag);
+
+    ue(pic_width_in_mbs_minus1,        0, H264_MAX_MB_WIDTH);
+    ue(pic_height_in_map_units_minus1, 0, H264_MAX_MB_HEIGHT);
+
+    flag(frame_mbs_only_flag);
+    if (!current->frame_mbs_only_flag)
+        flag(mb_adaptive_frame_field_flag);
+
+    flag(direct_8x8_inference_flag);
+
+    flag(frame_cropping_flag);
+    if (current->frame_cropping_flag) {
+        ue(frame_crop_left_offset,   0, H264_MAX_WIDTH);
+        ue(frame_crop_right_offset,  0, H264_MAX_WIDTH);
+        ue(frame_crop_top_offset,    0, H264_MAX_HEIGHT);
+        ue(frame_crop_bottom_offset, 0, H264_MAX_HEIGHT);
+    }
+
+    flag(vui_parameters_present_flag);
+    if (current->vui_parameters_present_flag)
+        CHECK(FUNC(vui_parameters)(ctx, rw, &current->vui, current));
+
+    CHECK(FUNC(rbsp_trailing_bits)(ctx, rw));
+
+    return 0;
+}
+
+static int FUNC(sps_extension)(CodedBitstreamContext *ctx, RWContext *rw,
+                               H264RawSPSExtension *current)
+{
+    int err;
+
+    HEADER("Sequence Parameter Set Extension");
+
+    CHECK(FUNC(nal_unit_header)(ctx, rw, &current->nal_unit_header,
+                                1 << H264_NAL_SPS_EXT));
+
+    ue(seq_parameter_set_id, 0, 31);
+
+    ue(aux_format_idc, 0, 3);
+
+    if (current->aux_format_idc != 0) {
+        int bits;
+
+        ue(bit_depth_aux_minus8, 0, 4);
+        flag(alpha_incr_flag);
+
+        bits = current->bit_depth_aux_minus8 + 9;
+        u(bits, alpha_opaque_value,      0, (1 << bits) - 1);
+        u(bits, alpha_transparent_value, 0, (1 << bits) - 1);
+    }
+
+    flag(additional_extension_flag);
+
+    CHECK(FUNC(rbsp_trailing_bits)(ctx, rw));
+
+    return 0;
+}
+
+static int FUNC(pps)(CodedBitstreamContext *ctx, RWContext *rw,
+                     H264RawPPS *current)
+{
+    CodedBitstreamH264Context *h264 = ctx->priv_data;
+    const H264RawSPS *sps;
+    int err, i;
+
+    HEADER("Picture Parameter Set");
+
+    CHECK(FUNC(nal_unit_header)(ctx, rw, &current->nal_unit_header,
+                                1 << H264_NAL_PPS));
+
+    ue(pic_parameter_set_id, 0, 255);
+    ue(seq_parameter_set_id, 0, 31);
+
+    sps = h264->sps[current->seq_parameter_set_id];
+    if (!sps) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "SPS id %d not available.\n",
+               current->seq_parameter_set_id);
+        return AVERROR_INVALIDDATA;
+    }
+
+    flag(entropy_coding_mode_flag);
+    flag(bottom_field_pic_order_in_frame_present_flag);
+
+    ue(num_slice_groups_minus1, 0, 7);
+    if (current->num_slice_groups_minus1 > 0) {
+        unsigned int pic_size;
+        int iGroup;
+
+        pic_size = (sps->pic_width_in_mbs_minus1 + 1) *
+                   (sps->pic_height_in_map_units_minus1 + 1);
+
+        ue(slice_group_map_type, 0, 6);
+
+        if (current->slice_group_map_type == 0) {
+            for (iGroup = 0; iGroup <= current->num_slice_groups_minus1; iGroup++)
+                ue(run_length_minus1[iGroup], 0, pic_size - 1);
+
+        } else if (current->slice_group_map_type == 2) {
+            for (iGroup = 0; iGroup < current->num_slice_groups_minus1; iGroup++) {
+                ue(top_left[iGroup],     0,                         pic_size - 1);
+                ue(bottom_right[iGroup], current->top_left[iGroup], pic_size - 1);
+            }
+        } else if (current->slice_group_map_type == 3 ||
+                   current->slice_group_map_type == 4 ||
+                   current->slice_group_map_type == 5) {
+            flag(slice_group_change_direction_flag);
+            ue(slice_group_change_rate_minus1, 0, pic_size - 1);
+        } else if (current->slice_group_map_type == 6) {
+            ue(pic_size_in_map_units_minus1, pic_size - 1, pic_size - 1);
+            for (i = 0; i <= current->pic_size_in_map_units_minus1; i++)
+                u(av_log2(2 * current->num_slice_groups_minus1 + 1),
+                  slice_group_id[i], 0, current->num_slice_groups_minus1);
+        }
+    }
+
+    ue(num_ref_idx_l0_default_active_minus1, 0, 31);
+    ue(num_ref_idx_l1_default_active_minus1, 0, 31);
+
+    flag(weighted_pred_flag);
+    u(2, weighted_bipred_idc, 0, 2);
+
+    se(pic_init_qp_minus26, -26 - 6 * sps->bit_depth_luma_minus8, +25);
+    se(pic_init_qs_minus26, -26, +25);
+    se(chroma_qp_index_offset, -12, +12);
+
+    flag(deblocking_filter_control_present_flag);
+    flag(constrained_intra_pred_flag);
+    flag(redundant_pic_cnt_present_flag);
+
+    if (more_rbsp_data(current->more_rbsp_data))
+    {
+        flag(transform_8x8_mode_flag);
+
+        flag(pic_scaling_matrix_present_flag);
+        if (current->pic_scaling_matrix_present_flag) {
+            for (i = 0; i < 6 + (((sps->chroma_format_idc != 3) ? 2 : 6) *
+                                 current->transform_8x8_mode_flag); i++) {
+                flag(pic_scaling_list_present_flag[i]);
+                if (current->pic_scaling_list_present_flag[i]) {
+                    if (i < 6)
+                        CHECK(FUNC(scaling_list)(ctx, rw,
+                                                 &current->scaling_list_4x4[i],
+                                                 16));
+                    else
+                        CHECK(FUNC(scaling_list)(ctx, rw,
+                                                 &current->scaling_list_8x8[i - 6],
+                                                 64));
+                }
+            }
+        }
+
+        se(second_chroma_qp_index_offset, -12, +12);
+    } else {
+        infer(transform_8x8_mode_flag, 0);
+        infer(pic_scaling_matrix_present_flag, 0);
+        infer(second_chroma_qp_index_offset, current->chroma_qp_index_offset);
+    }
+
+    CHECK(FUNC(rbsp_trailing_bits)(ctx, rw));
+
+    return 0;
+}
+
+static int FUNC(sei_buffering_period)(CodedBitstreamContext *ctx, RWContext *rw,
+                                      H264RawSEIBufferingPeriod *current)
+{
+    CodedBitstreamH264Context *h264 = ctx->priv_data;
+    const H264RawSPS *sps;
+    int err, i, length;
+
+    ue(seq_parameter_set_id, 0, 31);
+
+    sps = h264->sps[current->seq_parameter_set_id];
+    if (!sps) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "SPS id %d not available.\n",
+               current->seq_parameter_set_id);
+        return AVERROR_INVALIDDATA;
+    }
+    h264->active_sps = sps;
+
+    if (sps->vui.nal_hrd_parameters_present_flag) {
+        for (i = 0; i <= sps->vui.nal_hrd_parameters.cpb_cnt_minus1; i++) {
+            length = sps->vui.nal_hrd_parameters.initial_cpb_removal_delay_length_minus1 + 1;
+            xu(length, initial_cpb_removal_delay[SchedSelIdx],
+               current->nal.initial_cpb_removal_delay[i],
+               0, (1 << (uint64_t)length) - 1);
+            xu(length, initial_cpb_removal_delay_offset[SchedSelIdx],
+               current->nal.initial_cpb_removal_delay_offset[i],
+               0, (1 << (uint64_t)length) - 1);
+        }
+    }
+
+    if (sps->vui.vcl_hrd_parameters_present_flag) {
+        for (i = 0; i <= sps->vui.vcl_hrd_parameters.cpb_cnt_minus1; i++) {
+            length = sps->vui.vcl_hrd_parameters.initial_cpb_removal_delay_length_minus1 + 1;
+            xu(length, initial_cpb_removal_delay[SchedSelIdx],
+               current->vcl.initial_cpb_removal_delay[i],
+               0, (1 << (uint64_t)length) - 1);
+            xu(length, initial_cpb_removal_delay_offset[SchedSelIdx],
+               current->vcl.initial_cpb_removal_delay_offset[i],
+               0, (1 << (uint64_t)length) - 1);
+        }
+    }
+
+    return 0;
+}
+
+static int FUNC(sei_pic_timestamp)(CodedBitstreamContext *ctx, RWContext *rw,
+                                   H264RawSEIPicTimestamp *current)
+{
+    CodedBitstreamH264Context *h264 = ctx->priv_data;
+    const H264RawSPS *sps;
+    uint8_t time_offset_length;
+    int err;
+
+    u(2, ct_type, 0, 2);
+    flag(nuit_field_based_flag);
+    u(5, counting_type, 0, 6);
+    flag(full_timestamp_flag);
+    flag(discontinuity_flag);
+    flag(cnt_dropped_flag);
+    u(8, n_frames, 0, 255);
+    if (current->full_timestamp_flag) {
+            u(6, seconds_value, 0, 59);
+            u(6, minutes_value, 0, 59);
+            u(5, hours_value,   0, 23);
+    } else {
+        flag(seconds_flag);
+        if (current->seconds_flag) {
+            u(6, seconds_value, 0, 59);
+            flag(minutes_flag);
+            if (current->minutes_flag) {
+                u(6, minutes_value, 0, 59);
+                flag(hours_flag);
+                if (current->hours_flag)
+                    u(5, hours_value, 0, 23);
+            }
+        }
+    }
+
+    sps = h264->active_sps;
+    if (sps->vui.nal_hrd_parameters_present_flag)
+        time_offset_length = sps->vui.nal_hrd_parameters.time_offset_length;
+    else if (sps->vui.vcl_hrd_parameters_present_flag)
+        time_offset_length = sps->vui.vcl_hrd_parameters.time_offset_length;
+    else
+        time_offset_length = 24;
+
+    if (time_offset_length > 0)
+        u(time_offset_length, time_offset,
+          0, (1 << (uint64_t)time_offset_length) - 1);
+    else
+        infer(time_offset, 0);
+
+    return 0;
+}
+
+static int FUNC(sei_pic_timing)(CodedBitstreamContext *ctx, RWContext *rw,
+                                H264RawSEIPicTiming *current)
+{
+    CodedBitstreamH264Context *h264 = ctx->priv_data;
+    const H264RawSPS *sps;
+    int err;
+
+    sps = h264->active_sps;
+    if (!sps) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR,
+               "No active SPS for pic_timing.\n");
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (sps->vui.nal_hrd_parameters_present_flag ||
+        sps->vui.vcl_hrd_parameters_present_flag) {
+        const H264RawHRD *hrd;
+
+        if (sps->vui.nal_hrd_parameters_present_flag)
+            hrd = &sps->vui.nal_hrd_parameters;
+        else if (sps->vui.vcl_hrd_parameters_present_flag)
+            hrd = &sps->vui.vcl_hrd_parameters;
+        else {
+            av_log(ctx->log_ctx, AV_LOG_ERROR,
+                   "No HRD parameters for pic_timing.\n");
+            return AVERROR_INVALIDDATA;
+        }
+
+        u(hrd->cpb_removal_delay_length_minus1 + 1, cpb_removal_delay,
+          0, (1 << (uint64_t)hrd->cpb_removal_delay_length_minus1) + 1);
+        u(hrd->dpb_output_delay_length_minus1 + 1, dpb_output_delay,
+          0, (1 << (uint64_t)hrd->dpb_output_delay_length_minus1) + 1);
+    }
+
+    if (sps->vui.pic_struct_present_flag) {
+        static const int num_clock_ts[9] = {
+            1, 1, 1, 2, 2, 3, 3, 2, 3
+        };
+        int i;
+
+        u(4, pic_struct, 0, 8);
+        if (current->pic_struct > 8)
+            return AVERROR_INVALIDDATA;
+
+        for (i = 0; i < num_clock_ts[current->pic_struct]; i++) {
+            flag(clock_timestamp_flag[i]);
+            if (current->clock_timestamp_flag[i])
+                CHECK(FUNC(sei_pic_timestamp)(ctx, rw, &current->timestamp[i]));
+        }
+    }
+
+    return 0;
+}
+
+static int FUNC(sei_user_data_registered)(CodedBitstreamContext *ctx, RWContext *rw,
+                                          H264RawSEIUserDataRegistered *current,
+                                          uint32_t *payload_size)
+{
+    int err, i, j;
+
+    u(8, itu_t_t35_country_code, 0x00, 0xff);
+    if (current->itu_t_t35_country_code != 0xff)
+        i = 1;
+    else {
+        u(8, itu_t_t35_country_code_extension_byte, 0x00, 0xff);
+        i = 2;
+    }
+
+#ifdef READ
+    if (*payload_size < i) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR,
+               "Invalid SEI user data registered payload.\n");
+        return AVERROR_INVALIDDATA;
+    }
+    current->data_length = *payload_size - i;
+#else
+    *payload_size = i + current->data_length;
+#endif
+
+    allocate(current->data, current->data_length);
+    for (j = 0; j < current->data_length; j++)
+        xu(8, itu_t_t35_payload_byte, current->data[j], 0x00, 0xff);
+
+    return 0;
+}
+
+static int FUNC(sei_user_data_unregistered)(CodedBitstreamContext *ctx, RWContext *rw,
+                                            H264RawSEIUserDataUnregistered *current,
+                                            uint32_t *payload_size)
+{
+    int err, i;
+
+#ifdef READ
+    if (*payload_size < 16) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR,
+               "Invalid SEI user data unregistered payload.\n");
+        return AVERROR_INVALIDDATA;
+    }
+    current->data_length = *payload_size - 16;
+#else
+    *payload_size = 16 + current->data_length;
+#endif
+
+    for (i = 0; i < 16; i++) {
+        xu(8, uuid_iso_iec_11578,
+           current->uuid_iso_iec_11578[i], 0x00, 0xff);
+    }
+
+    allocate(current->data, current->data_length);
+
+    for (i = 0; i < current->data_length; i++)
+        xu(8, user_data_payload_byte, current->data[i], 0x00, 0xff);
+
+    return 0;
+}
+
+static int FUNC(sei_recovery_point)(CodedBitstreamContext *ctx, RWContext *rw,
+                                    H264RawSEIRecoveryPoint *current)
+{
+    int err;
+
+    ue(recovery_frame_cnt, 0, 65535);
+    flag(exact_match_flag);
+    flag(broken_link_flag);
+    u(2, changing_slice_group_idc, 0, 2);
+
+    return 0;
+}
+
+static int FUNC(sei_display_orientation)(CodedBitstreamContext *ctx, RWContext *rw,
+                                         H264RawSEIDisplayOrientation *current)
+{
+    int err;
+
+    flag(display_orientation_cancel_flag);
+    if (!current->display_orientation_cancel_flag) {
+        flag(hor_flip);
+        flag(ver_flip);
+        u(16, anticlockwise_rotation, 0, 65535);
+        ue(display_orientation_repetition_period, 0, 16384);
+        flag(display_orientation_extension_flag);
+    }
+
+    return 0;
+}
+
+static int FUNC(sei_payload)(CodedBitstreamContext *ctx, RWContext *rw,
+                             H264RawSEIPayload *current)
+{
+    int err, i;
+    int start_position, end_position;
+
+#ifdef READ
+    start_position = get_bits_count(rw);
+#else
+    start_position = put_bits_count(rw);
+#endif
+
+    switch (current->payload_type) {
+    case H264_SEI_TYPE_BUFFERING_PERIOD:
+        CHECK(FUNC(sei_buffering_period)
+              (ctx, rw, &current->payload.buffering_period));
+        break;
+    case H264_SEI_TYPE_PIC_TIMING:
+        CHECK(FUNC(sei_pic_timing)
+              (ctx, rw, &current->payload.pic_timing));
+        break;
+    case H264_SEI_TYPE_FILLER_PAYLOAD:
+        {
+            av_unused int ff_byte = 0xff;
+            for (i = 0; i  < current->payload_size; i++)
+                xu(8, ff_byte, ff_byte, 0xff, 0xff);
+        }
+        break;
+    case H264_SEI_TYPE_USER_DATA_REGISTERED:
+        CHECK(FUNC(sei_user_data_registered)
+              (ctx, rw, &current->payload.user_data_registered, &current->payload_size));
+        break;
+    case H264_SEI_TYPE_USER_DATA_UNREGISTERED:
+        CHECK(FUNC(sei_user_data_unregistered)
+              (ctx, rw, &current->payload.user_data_unregistered, &current->payload_size));
+        break;
+    case H264_SEI_TYPE_RECOVERY_POINT:
+        CHECK(FUNC(sei_recovery_point)
+              (ctx, rw, &current->payload.recovery_point));
+        break;
+    case H264_SEI_TYPE_DISPLAY_ORIENTATION:
+        CHECK(FUNC(sei_display_orientation)
+              (ctx, rw, &current->payload.display_orientation));
+        break;
+    default:
+        {
+            allocate(current->payload.other.data, current->payload_size);
+            for (i = 0; i < current->payload_size; i++)
+                xu(8, payload_byte, current->payload.other.data[i], 0, 255);
+        }
+    }
+
+    if (byte_alignment(rw)) {
+        av_unused int one = 1, zero = 0;
+        xu(1, bit_equal_to_one, one, 1, 1);
+        while (byte_alignment(rw))
+            xu(1, bit_equal_to_zero, zero, 0, 0);
+    }
+
+#ifdef READ
+    end_position = get_bits_count(rw);
+    if (end_position < start_position + 8 * current->payload_size) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Incorrect SEI payload length: "
+               "header %d bits, actually %d bits.\n",
+               8 * current->payload_size,
+               end_position - start_position);
+        return AVERROR_INVALIDDATA;
+    }
+#else
+    end_position = put_bits_count(rw);
+    current->payload_size = (end_position - start_position) / 8;
+#endif
+
+    return 0;
+}
+
+static int FUNC(sei)(CodedBitstreamContext *ctx, RWContext *rw,
+                     H264RawSEI *current)
+{
+    int err, k;
+
+    HEADER("Supplemental Enhancement Information");
+
+    CHECK(FUNC(nal_unit_header)(ctx, rw, &current->nal_unit_header,
+                                1 << H264_NAL_SEI));
+
+#ifdef READ
+    for (k = 0; k < H264_MAX_SEI_PAYLOADS; k++) {
+        uint32_t payload_type = 0;
+        uint32_t payload_size = 0;
+        uint32_t tmp;
+
+        while (show_bits(rw, 8) == 0xff) {
+            xu(8, ff_byte, tmp, 0xff, 0xff);
+            payload_type += 255;
+        }
+        xu(8, last_payload_type_byte, tmp, 0, 254);
+        payload_type += tmp;
+
+        while (show_bits(rw, 8) == 0xff) {
+            xu(8, ff_byte, tmp, 0xff, 0xff);
+            payload_size += 255;
+        }
+        xu(8, last_payload_size_byte, tmp, 0, 254);
+        payload_size += tmp;
+
+        current->payload[k].payload_type = payload_type;
+        current->payload[k].payload_size = payload_size;
+
+        CHECK(FUNC(sei_payload)(ctx, rw, &current->payload[k]));
+
+        if (!cbs_h2645_read_more_rbsp_data(rw))
+            break;
+    }
+    if (k >= H264_MAX_SEI_PAYLOADS) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Too many payloads in "
+               "SEI message: found %d.\n", k);
+        return AVERROR_INVALIDDATA;
+    }
+    current->payload_count = k + 1;
+#else
+    for (k = 0; k < current->payload_count; k++) {
+        PutBitContext start_state;
+        uint32_t tmp;
+        int need_size, i;
+
+        // Somewhat clumsy: we write the payload twice when
+        // we don't know the size in advance.  This will mess
+        // with trace output, but is otherwise harmless.
+        start_state = *rw;
+        need_size = !current->payload[k].payload_size;
+        for (i = 0; i < 1 + need_size; i++) {
+            *rw = start_state;
+
+            tmp = current->payload[k].payload_type;
+            while (tmp >= 255) {
+                xu(8, ff_byte, 0xff, 0xff, 0xff);
+                tmp -= 255;
+            }
+            xu(8, last_payload_type_byte, tmp, 0, 254);
+
+            tmp = current->payload[k].payload_size;
+            while (tmp >= 255) {
+                xu(8, ff_byte, 0xff, 0xff, 0xff);
+                tmp -= 255;
+            }
+            xu(8, last_payload_size_byte, tmp, 0, 254);
+
+            CHECK(FUNC(sei_payload)(ctx, rw, &current->payload[k]));
+        }
+    }
+#endif
+
+    CHECK(FUNC(rbsp_trailing_bits)(ctx, rw));
+
+    return 0;
+}
+
+static int FUNC(aud)(CodedBitstreamContext *ctx, RWContext *rw,
+                     H264RawAUD *current)
+{
+    int err;
+
+    HEADER("Access Unit Delimiter");
+
+    CHECK(FUNC(nal_unit_header)(ctx, rw, &current->nal_unit_header,
+                                1 << H264_NAL_AUD));
+
+    u(3, primary_pic_type, 0, 7);
+
+    CHECK(FUNC(rbsp_trailing_bits)(ctx, rw));
+
+    return 0;
+}
+
+static int FUNC(ref_pic_list_modification)(CodedBitstreamContext *ctx, RWContext *rw,
+                                           H264RawSliceHeader *current)
+{
+    CodedBitstreamH264Context *h264 = ctx->priv_data;
+    const H264RawSPS *sps = h264->active_sps;
+    int err, i, mopn;
+
+    if (current->slice_type % 5 != 2 &&
+        current->slice_type % 5 != 4) {
+        flag(ref_pic_list_modification_flag_l0);
+        if (current->ref_pic_list_modification_flag_l0) {
+            for (i = 0; i < H264_MAX_RPLM_COUNT; i++) {
+                xue(modification_of_pic_nums_idc,
+                    current->rplm_l0[i].modification_of_pic_nums_idc, 0, 3);
+
+                mopn = current->rplm_l0[i].modification_of_pic_nums_idc;
+                if (mopn == 3)
+                    break;
+
+                if (mopn == 0 || mopn == 1)
+                    xue(abs_diff_pic_num_minus1,
+                        current->rplm_l0[i].abs_diff_pic_num_minus1,
+                        0, (1 + current->field_pic_flag) *
+                        (1 << (sps->log2_max_frame_num_minus4 + 4)));
+                else if (mopn == 2)
+                    xue(long_term_pic_num,
+                        current->rplm_l0[i].long_term_pic_num,
+                        0, sps->max_num_ref_frames - 1);
+            }
+        }
+    }
+
+    if (current->slice_type % 5 == 1) {
+        flag(ref_pic_list_modification_flag_l1);
+        if (current->ref_pic_list_modification_flag_l1) {
+            for (i = 0; i < H264_MAX_RPLM_COUNT; i++) {
+                xue(modification_of_pic_nums_idc,
+                    current->rplm_l1[i].modification_of_pic_nums_idc, 0, 3);
+
+                mopn = current->rplm_l1[i].modification_of_pic_nums_idc;
+                if (mopn == 3)
+                    break;
+
+                if (mopn == 0 || mopn == 1)
+                    xue(abs_diff_pic_num_minus1,
+                        current->rplm_l1[i].abs_diff_pic_num_minus1,
+                        0, (1 + current->field_pic_flag) *
+                        (1 << (sps->log2_max_frame_num_minus4 + 4)));
+                else if (mopn == 2)
+                    xue(long_term_pic_num,
+                        current->rplm_l1[i].long_term_pic_num,
+                        0, sps->max_num_ref_frames - 1);
+            }
+        }
+    }
+
+    return 0;
+}
+
+static int FUNC(pred_weight_table)(CodedBitstreamContext *ctx, RWContext *rw,
+                                   H264RawSliceHeader *current)
+{
+    CodedBitstreamH264Context *h264 = ctx->priv_data;
+    const H264RawSPS *sps = h264->active_sps;
+    int chroma;
+    int err, i, j;
+
+    ue(luma_log2_weight_denom, 0, 7);
+
+    chroma = !sps->separate_colour_plane_flag && sps->chroma_format_idc != 0;
+    if (chroma)
+        ue(chroma_log2_weight_denom, 0, 7);
+
+    for (i = 0; i <= current->num_ref_idx_l0_active_minus1; i++) {
+        flag(luma_weight_l0_flag[i]);
+        if (current->luma_weight_l0_flag[i]) {
+            se(luma_weight_l0[i], -128, +127);
+            se(luma_offset_l0[i], -128, +127);
+        }
+        if (chroma) {
+            flag(chroma_weight_l0_flag[i]);
+            if (current->chroma_weight_l0_flag[i]) {
+                for (j = 0; j < 2; j++) {
+                    se(chroma_weight_l0[i][j], -128, +127);
+                    se(chroma_offset_l0[i][j], -128, +127);
+                }
+            }
+        }
+    }
+
+    if (current->slice_type % 5 == 1) {
+        for (i = 0; i <= current->num_ref_idx_l1_active_minus1; i++) {
+            flag(luma_weight_l1_flag[i]);
+            if (current->luma_weight_l1_flag[i]) {
+                se(luma_weight_l1[i], -128, +127);
+                se(luma_offset_l1[i], -128, +127);
+            }
+            if (chroma) {
+                flag(chroma_weight_l1_flag[i]);
+                if (current->chroma_weight_l1_flag[i]) {
+                    for (j = 0; j < 2; j++) {
+                        se(chroma_weight_l1[i][j], -128, +127);
+                        se(chroma_offset_l1[i][j], -128, +127);
+                    }
+                }
+            }
+        }
+    }
+
+    return 0;
+}
+
+static int FUNC(dec_ref_pic_marking)(CodedBitstreamContext *ctx, RWContext *rw,
+                                     H264RawSliceHeader *current, int idr_pic_flag)
+{
+    CodedBitstreamH264Context *h264 = ctx->priv_data;
+    const H264RawSPS *sps = h264->active_sps;
+    int err, i;
+    uint32_t mmco;
+
+    if (idr_pic_flag) {
+        flag(no_output_of_prior_pics_flag);
+        flag(long_term_reference_flag);
+    } else {
+        flag(adaptive_ref_pic_marking_mode_flag);
+        if (current->adaptive_ref_pic_marking_mode_flag) {
+            for (i = 0; i < H264_MAX_MMCO_COUNT; i++) {
+                xue(memory_management_control_operation,
+                    current->mmco[i].memory_management_control_operation,
+                    0, 6);
+
+                mmco = current->mmco[i].memory_management_control_operation;
+                if (mmco == 0)
+                    break;
+
+                if (mmco == 1 || mmco == 3)
+                    xue(difference_of_pic_nums_minus1,
+                        current->mmco[i].difference_of_pic_nums_minus1,
+                        0, INT32_MAX);
+                if (mmco == 2)
+                    xue(long_term_pic_num,
+                        current->mmco[i].long_term_pic_num,
+                        0, sps->max_num_ref_frames - 1);
+                if (mmco == 3 || mmco == 6)
+                    xue(long_term_frame_idx,
+                        current->mmco[i].long_term_frame_idx,
+                        0, sps->max_num_ref_frames - 1);
+                if (mmco == 4)
+                    xue(max_long_term_frame_idx_plus1,
+                        current->mmco[i].max_long_term_frame_idx_plus1,
+                        0, sps->max_num_ref_frames);
+            }
+            if (i == H264_MAX_MMCO_COUNT) {
+                av_log(ctx->log_ctx, AV_LOG_ERROR, "Too many "
+                       "memory management control operations.\n");
+                return AVERROR_INVALIDDATA;
+            }
+        }
+    }
+
+    return 0;
+}
+
+static int FUNC(slice_header)(CodedBitstreamContext *ctx, RWContext *rw,
+                              H264RawSliceHeader *current)
+{
+    CodedBitstreamH264Context *h264 = ctx->priv_data;
+    const H264RawSPS *sps;
+    const H264RawPPS *pps;
+    int err;
+    int idr_pic_flag;
+    int slice_type_i, slice_type_p, slice_type_b;
+    int slice_type_si, slice_type_sp;
+
+    HEADER("Slice Header");
+
+    CHECK(FUNC(nal_unit_header)(ctx, rw, &current->nal_unit_header,
+                                1 << H264_NAL_SLICE     |
+                                1 << H264_NAL_IDR_SLICE |
+                                1 << H264_NAL_AUXILIARY_SLICE));
+
+    if (current->nal_unit_header.nal_unit_type == H264_NAL_AUXILIARY_SLICE) {
+        if (!h264->last_slice_nal_unit_type) {
+            av_log(ctx->log_ctx, AV_LOG_ERROR, "Auxiliary slice "
+                   "is not decodable without the main picture "
+                   "in the same access unit.\n");
+            return AVERROR_INVALIDDATA;
+        }
+    } else {
+        h264->last_slice_nal_unit_type =
+            current->nal_unit_header.nal_unit_type;
+    }
+    idr_pic_flag = h264->last_slice_nal_unit_type == H264_NAL_IDR_SLICE;
+
+    ue(first_mb_in_slice, 0, H264_MAX_MB_PIC_SIZE - 1);
+    ue(slice_type, 0, 9);
+
+    slice_type_i  = current->slice_type % 5 == 2;
+    slice_type_p  = current->slice_type % 5 == 0;
+    slice_type_b  = current->slice_type % 5 == 1;
+    slice_type_si = current->slice_type % 5 == 4;
+    slice_type_sp = current->slice_type % 5 == 3;
+
+    if (idr_pic_flag && !(slice_type_i || slice_type_si)) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid slice type %d "
+               "for IDR picture.\n", current->slice_type);
+        return AVERROR_INVALIDDATA;
+    }
+
+    ue(pic_parameter_set_id, 0, 255);
+
+    pps = h264->pps[current->pic_parameter_set_id];
+    if (!pps) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "PPS id %d not available.\n",
+               current->pic_parameter_set_id);
+        return AVERROR_INVALIDDATA;
+    }
+    h264->active_pps = pps;
+
+    sps = h264->sps[pps->seq_parameter_set_id];
+    if (!sps) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "SPS id %d not available.\n",
+               pps->seq_parameter_set_id);
+        return AVERROR_INVALIDDATA;
+    }
+    h264->active_sps = sps;
+
+    if (sps->separate_colour_plane_flag)
+        u(2, colour_plane_id, 0, 2);
+
+    u(sps->log2_max_frame_num_minus4 + 4, frame_num,
+      0, (1 << (sps->log2_max_frame_num_minus4 + 4)) - 1);
+
+    if (!sps->frame_mbs_only_flag) {
+        flag(field_pic_flag);
+        if (current->field_pic_flag)
+            flag(bottom_field_flag);
+        else
+            infer(bottom_field_flag, 0);
+    } else {
+        infer(field_pic_flag,    0);
+        infer(bottom_field_flag, 0);
+    }
+
+    if (idr_pic_flag)
+        ue(idr_pic_id, 0, 65535);
+
+    if (sps->pic_order_cnt_type == 0) {
+        u(sps->log2_max_pic_order_cnt_lsb_minus4 + 4, pic_order_cnt_lsb,
+          0, (1 << (sps->log2_max_pic_order_cnt_lsb_minus4 + 4)) - 1);
+        if (pps->bottom_field_pic_order_in_frame_present_flag &&
+            !current->field_pic_flag)
+            se(delta_pic_order_cnt_bottom, INT32_MIN + 1, INT32_MAX);
+
+    } else if (sps->pic_order_cnt_type == 1) {
+        if (!sps->delta_pic_order_always_zero_flag) {
+            se(delta_pic_order_cnt[0], INT32_MIN + 1, INT32_MAX);
+            if (pps->bottom_field_pic_order_in_frame_present_flag &&
+                !current->field_pic_flag)
+                se(delta_pic_order_cnt[1], INT32_MIN + 1, INT32_MAX);
+            else
+                infer(delta_pic_order_cnt[1], 0);
+        } else {
+            infer(delta_pic_order_cnt[0], 0);
+            infer(delta_pic_order_cnt[1], 0);
+        }
+    }
+
+    if (pps->redundant_pic_cnt_present_flag)
+        ue(redundant_pic_cnt, 0, 127);
+
+    if (slice_type_b)
+        flag(direct_spatial_mv_pred_flag);
+
+    if (slice_type_p || slice_type_sp || slice_type_b) {
+        flag(num_ref_idx_active_override_flag);
+        if (current->num_ref_idx_active_override_flag) {
+            ue(num_ref_idx_l0_active_minus1, 0, 31);
+            if (slice_type_b)
+                ue(num_ref_idx_l1_active_minus1, 0, 31);
+        } else {
+            infer(num_ref_idx_l0_active_minus1,
+                  pps->num_ref_idx_l0_default_active_minus1);
+            infer(num_ref_idx_l1_active_minus1,
+                  pps->num_ref_idx_l1_default_active_minus1);
+        }
+    }
+
+    if (current->nal_unit_header.nal_unit_type == 20 ||
+        current->nal_unit_header.nal_unit_type == 21) {
+        av_log(ctx->log_ctx, AV_LOG_ERROR, "MVC / 3DAVC not supported.\n");
+        return AVERROR_PATCHWELCOME;
+    } else {
+        CHECK(FUNC(ref_pic_list_modification)(ctx, rw, current));
+    }
+
+    if ((pps->weighted_pred_flag && (slice_type_p || slice_type_sp)) ||
+        (pps->weighted_bipred_idc == 1 && slice_type_b)) {
+        CHECK(FUNC(pred_weight_table)(ctx, rw, current));
+    }
+
+    if (current->nal_unit_header.nal_ref_idc != 0) {
+        CHECK(FUNC(dec_ref_pic_marking)(ctx, rw, current, idr_pic_flag));
+    }
+
+    if (pps->entropy_coding_mode_flag &&
+        !slice_type_i && !slice_type_si) {
+        ue(cabac_init_idc, 0, 2);
+    }
+
+    se(slice_qp_delta, - 51 - 6 * sps->bit_depth_luma_minus8,
+                       + 51 + 6 * sps->bit_depth_luma_minus8);
+    if (slice_type_sp || slice_type_si) {
+        if (slice_type_sp)
+            flag(sp_for_switch_flag);
+        se(slice_qs_delta, -51, +51);
+    }
+
+    if (pps->deblocking_filter_control_present_flag) {
+        ue(disable_deblocking_filter_idc, 0, 2);
+        if (current->disable_deblocking_filter_idc != 1) {
+            se(slice_alpha_c0_offset_div2, -6, +6);
+            se(slice_beta_offset_div2,     -6, +6);
+        } else {
+            infer(slice_alpha_c0_offset_div2, 0);
+            infer(slice_beta_offset_div2,     0);
+        }
+    } else {
+        infer(disable_deblocking_filter_idc, 0);
+        infer(slice_alpha_c0_offset_div2,    0);
+        infer(slice_beta_offset_div2,        0);
+    }
+
+    if (pps->num_slice_groups_minus1 > 0 &&
+        pps->slice_group_map_type >= 3 &&
+        pps->slice_group_map_type <= 5) {
+        unsigned int pic_size, max, bits;
+
+        pic_size = (sps->pic_width_in_mbs_minus1 + 1) *
+                   (sps->pic_height_in_map_units_minus1 + 1);
+        max = (pic_size + pps->slice_group_change_rate_minus1) /
+              (pps->slice_group_change_rate_minus1 + 1);
+        bits = av_log2(2 * max - 1);
+
+        u(bits, slice_group_change_cycle, 0, max);
+    }
+
+    if (pps->entropy_coding_mode_flag) {
+        av_unused int one = 1;
+        while (byte_alignment(rw))
+            xu(1, cabac_alignment_one_bit, one, 1, 1);
+    }
+
+    return 0;
+}
diff --git a/libavcodec/cbs_internal.h b/libavcodec/cbs_internal.h
index f6a42beea3..2d417d4a40 100644
--- a/libavcodec/cbs_internal.h
+++ b/libavcodec/cbs_internal.h
@@ -83,4 +83,7 @@ int ff_cbs_write_unsigned(CodedBitstreamContext *ctx, PutBitContext *pbc,
                           uint32_t range_min, uint32_t range_max);
 
 
+extern const CodedBitstreamType ff_cbs_type_h264;
+
+
 #endif /* AVCODEC_CBS_INTERNAL_H */
