[FFmpeg-devel] [PATCH v4] avcodec/cbs_vp8: Add support for VP8 codec bitstream

Dai, Jianhui J jianhui.j.dai at intel.com
Fri Aug 25 06:17:16 EEST 2023



> -----Original Message-----
> From: ffmpeg-devel <ffmpeg-devel-bounces at ffmpeg.org> On Behalf Of Dai,
> Jianhui J
> Sent: Friday, August 25, 2023 10:40 AM
> To: ffmpeg-devel at ffmpeg.org
> Subject: [FFmpeg-devel] [PATCH v4] avcodec/cbs_vp8: Add support for VP8
> codec bitstream
> 
> This commit adds support for VP8 bitstream read methods to the cbs codec.
> This enables the trace_headers bitstream filter to support VP8, in addition to
> AV1, H.264, H.265, and VP9. This can be useful for debugging VP8 stream
> issues.
> 
> The CBS VP8 implements a simple VP8 boolean decoder with bounds
> checking to prevent overreads.
> 
> Only the read methods `read_unit` and `split_fragment` are implemented.
> The write methods `write_unit` and `assemble_fragment` return the error
> code AVERROR_PATCHWELCOME. This is because CBS VP8 write is unlikely to
> be used by any applications at the moment. The write methods can be added
> later if there is a real need for them.
> 
> TESTS: ffmpeg -i fate-suite/vp8/frame_size_change.webm -vcodec copy -bsf:v
> trace_headers -f null -
> 
> Signed-off-by: Jianhui Dai <jianhui.j.dai at intel.com>
> ---
>  configure                            |   4 +-
>  libavcodec/Makefile                  |   1 +
>  libavcodec/cbs.c                     |   6 +
>  libavcodec/cbs_internal.h            |   1 +
>  libavcodec/cbs_vp8.c                 | 591 +++++++++++++++++++++++++++
>  libavcodec/cbs_vp8.h                 | 137 +++++++
>  libavcodec/cbs_vp8_syntax_template.c | 248 +++++++++++
>  7 files changed, 987 insertions(+), 1 deletion(-)  create mode 100644
> libavcodec/cbs_vp8.c  create mode 100644 libavcodec/cbs_vp8.h  create
> mode 100644 libavcodec/cbs_vp8_syntax_template.c
> 
> diff --git a/configure b/configure
> index 932998b8d6..2424ee61ad 100755
> --- a/configure
> +++ b/configure
> @@ -2479,6 +2479,7 @@ CONFIG_EXTRA="
>      cbs_h266
>      cbs_jpeg
>      cbs_mpeg2
> +    cbs_vp8
>      cbs_vp9
>      deflate_wrapper
>      dirac_parse
> @@ -2764,6 +2765,7 @@ cbs_h265_select="cbs"
>  cbs_h266_select="cbs"
>  cbs_jpeg_select="cbs"
>  cbs_mpeg2_select="cbs"
> +cbs_vp8_select="cbs"
>  cbs_vp9_select="cbs"
>  dct_select="rdft"
>  deflate_wrapper_deps="zlib"
> @@ -3349,7 +3351,7 @@ h264_redundant_pps_bsf_select="cbs_h264"
>  hevc_metadata_bsf_select="cbs_h265"
>  mjpeg2jpeg_bsf_select="jpegtables"
>  mpeg2_metadata_bsf_select="cbs_mpeg2"
> -trace_headers_bsf_select="cbs"
> +trace_headers_bsf_select="cbs cbs_vp8"
>  vp9_metadata_bsf_select="cbs_vp9"
>  vvc_metadata_bsf_select="cbs_h266"
> 
> diff --git a/libavcodec/Makefile b/libavcodec/Makefile index
> 3c16b51462..04f735f45e 100644
> --- a/libavcodec/Makefile
> +++ b/libavcodec/Makefile
> @@ -79,6 +79,7 @@ OBJS-$(CONFIG_CBS_H265)                += cbs_h2645.o
> cbs_sei.o h2645_parse.o
>  OBJS-$(CONFIG_CBS_H266)                += cbs_h2645.o cbs_sei.o h2645_parse.o
>  OBJS-$(CONFIG_CBS_JPEG)                += cbs_jpeg.o
>  OBJS-$(CONFIG_CBS_MPEG2)               += cbs_mpeg2.o
> +OBJS-$(CONFIG_CBS_VP8)                 += cbs_vp8.o
>  OBJS-$(CONFIG_CBS_VP9)                 += cbs_vp9.o
>  OBJS-$(CONFIG_CRYSTALHD)               += crystalhd.o
>  OBJS-$(CONFIG_DCT)                     += dct.o dct32_fixed.o dct32_float.o
> diff --git a/libavcodec/cbs.c b/libavcodec/cbs.c index 3ec8285e21..f891e7247f
> 100644
> --- a/libavcodec/cbs.c
> +++ b/libavcodec/cbs.c
> @@ -49,6 +49,9 @@ static const CodedBitstreamType *const
> cbs_type_table[] = {  #if CONFIG_CBS_MPEG2
>      &ff_cbs_type_mpeg2,
>  #endif
> +#if CONFIG_CBS_VP8
> +    &ff_cbs_type_vp8,
> +#endif
>  #if CONFIG_CBS_VP9
>      &ff_cbs_type_vp9,
>  #endif
> @@ -73,6 +76,9 @@ const enum AVCodecID ff_cbs_all_codec_ids[] = {  #if
> CONFIG_CBS_MPEG2
>      AV_CODEC_ID_MPEG2VIDEO,
>  #endif
> +#if CONFIG_CBS_VP8
> +    AV_CODEC_ID_VP8,
> +#endif
>  #if CONFIG_CBS_VP9
>      AV_CODEC_ID_VP9,
>  #endif
> diff --git a/libavcodec/cbs_internal.h b/libavcodec/cbs_internal.h index
> da84697a29..7ae7e477d6 100644
> --- a/libavcodec/cbs_internal.h
> +++ b/libavcodec/cbs_internal.h
> @@ -263,6 +263,7 @@ extern const CodedBitstreamType ff_cbs_type_h265;
> extern const CodedBitstreamType ff_cbs_type_h266;  extern const
> CodedBitstreamType ff_cbs_type_jpeg;  extern const CodedBitstreamType
> ff_cbs_type_mpeg2;
> +extern const CodedBitstreamType ff_cbs_type_vp8;
>  extern const CodedBitstreamType ff_cbs_type_vp9;
> 
> 
> diff --git a/libavcodec/cbs_vp8.c b/libavcodec/cbs_vp8.c new file mode
> 100644 index 0000000000..6db295ce08
> --- /dev/null
> +++ b/libavcodec/cbs_vp8.c
> @@ -0,0 +1,591 @@
> +/*
> + * 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_vp8.h"
> +
> +#include <stdbool.h>
> +
> +#define DEFAULT_PROB 0x80
> +
> +static const uint8_t vp8_token_update_probs[4][8][3][11] = {
> +    {
> +        {
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {176, 246, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {223, 241, 252, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {249, 253, 253, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 244, 252, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {234, 254, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {253, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 246, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {239, 253, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {254, 255, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 248, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {251, 255, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 253, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {251, 254, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {254, 255, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 254, 253, 255, 254, 255, 255, 255, 255, 255, 255},
> +            {250, 255, 254, 255, 254, 255, 255, 255, 255, 255, 255},
> +            {254, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +    },
> +    {
> +        {
> +            {217, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {225, 252, 241, 253, 255, 255, 254, 255, 255, 255, 255},
> +            {234, 250, 241, 250, 253, 255, 253, 254, 255, 255, 255},
> +        },
> +        {
> +            {255, 254, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {223, 254, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {238, 253, 254, 254, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 248, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {249, 254, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 253, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {247, 254, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 253, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {252, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 254, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {253, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 254, 253, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {250, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {254, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +    },
> +    {
> +        {
> +            {186, 251, 250, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {234, 251, 244, 254, 255, 255, 255, 255, 255, 255, 255},
> +            {251, 251, 243, 253, 254, 255, 254, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 253, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {236, 253, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {251, 253, 253, 254, 254, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 254, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {254, 254, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 254, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {254, 254, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {254, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {254, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +    },
> +    {
> +        {
> +            {248, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {250, 254, 252, 254, 255, 255, 255, 255, 255, 255, 255},
> +            {248, 254, 249, 253, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 253, 253, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {246, 253, 253, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {252, 254, 251, 254, 254, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 254, 252, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {248, 254, 253, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {253, 255, 254, 254, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 251, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {245, 251, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {253, 253, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 251, 253, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {252, 253, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 254, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 252, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {249, 255, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 254, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 255, 253, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {250, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +        {
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {254, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +            {255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255},
> +        },
> +    },
> +};
> +
> +typedef struct CBSVP8BoolDecoder {
> +    const uint8_t *buffer;
> +    int buffer_size;
> +    int buffer_pos;
> +
> +    uint16_t value;
> +    uint8_t range;
> +
> +    int count; // Store the number of bits in the `value` buffer.
> +} CBSVP8BoolDecoder;
> +
> +static int cbs_vp8_bool_decoder_init(CBSVP8BoolDecoder *decoder,
> +                                     const uint8_t *buffer, const int
> +size) {
> +    av_assert0(decoder);
> +
> +    if (decoder->buffer == NULL || decoder->buffer <= 0) {
> +        return AVERROR_INVALIDDATA;
> +    }
> +
> +    decoder->buffer = buffer;
> +    decoder->buffer_size = size;
> +    decoder->buffer_pos = 0;
> +
> +    decoder->value = 0;
> +    decoder->range = 255;
> +
> +    decoder->count = 0;
> +
> +    return 0;
> +}
> +
> +static bool cbs_vp8_bool_decoder_fill_value(CBSVP8BoolDecoder *decoder)
> +{
> +    int shift = 8 - decoder->count;
> +
> +    av_assert0(decoder->count < 8);
> +
> +    // End of buffer.
> +    if (decoder->buffer_pos >= decoder->buffer_size) {
> +        return false;
> +    }
> +
> +    while (shift >= 0 && decoder->buffer_pos < decoder->buffer_size) {
> +        decoder->value |= *(decoder->buffer + decoder->buffer_pos++) <<
> + shift;
> +
> +        decoder->count += 8;
> +        shift -= 8;
> +    }
> +
> +    return (decoder->count >= 8);
> +}
> +
> +static int cbs_vp8_bool_decoder_read_bool(CBSVP8BoolDecoder *decoder,
> +                                          const uint8_t prob, uint8_t
> +*output) {
> +    uint8_t split = 1 + (((decoder->range - 1) * prob) >> 8);
> +    uint16_t big_split = split << 8;
> +
> +    if (decoder->count < 8 && !cbs_vp8_bool_decoder_fill_value(decoder)) {
> +        return AVERROR_INVALIDDATA;
> +    }
> +
> +    av_assert0(decoder->count >= 8);
> +    if (decoder->value >= big_split) {
> +        *output = 1;
> +        decoder->range -= split;
> +        decoder->value -= big_split;
> +    } else {
> +        *output = 0;
> +        decoder->range = split;
> +    }
> +
> +    while (decoder->range < 128) {
> +        decoder->value <<= 1;
> +        decoder->range <<= 1;
> +        --decoder->count;
> +    }
> +
> +    return 0;
> +}
> +
> +static int cbs_vp8_bool_decoder_read_literal(CBSVP8BoolDecoder *decoder,
> +                                             const uint8_t prob,
> +                                             uint32_t num_bits,
> +                                             uint32_t *output) {
> +    int ret = 0;
> +
> +    av_assert0(num_bits <= 32);
> +
> +    *output = 0;
> +    for (; num_bits > 0; --num_bits) {
> +        uint8_t bit_output = 0;
> +        if ((ret = cbs_vp8_bool_decoder_read_bool(decoder, prob,
> +                                                  &bit_output)) != 0) {
> +            return ret;
> +        }
> +
> +        *output = (*output << 1) | bit_output;
> +    }
> +
> +    return 0;
> +}
> +
> +static int cbs_vp8_bool_decoder_bit_count(CBSVP8BoolDecoder
> +*bool_decoder) {
> +    return (bool_decoder->buffer_pos * 8 - bool_decoder->count); }
> +
> +static int cbs_vp8_bool_decoder_read_unsigned(
> +    CodedBitstreamContext *ctx, CBSVP8BoolDecoder *bool_decoder, int
> width,
> +    uint8_t prob, const char *name, const int *subscripts, uint32_t *write_to,
> +    bool trace_enable)
> +{
> +    int ret = 0;
> +    CodedBitstreamVP8Context *vp8 = ctx->priv_data;
> +    uint32_t value;
> +    int pos;
> +
> +    av_assert0(width >= 0 && width <= 8);
> +
> +    pos = vp8->uncompressed_header_size * 8;
> +    pos += cbs_vp8_bool_decoder_bit_count(bool_decoder);
> +
> +    ret = cbs_vp8_bool_decoder_read_literal(bool_decoder, prob, width,
> &value);
> +    if (ret != 0) {
> +        return ret;
> +    }
> +
> +    if (ctx->trace_enable && trace_enable) {
> +        char bits[33] = "-";
> +        ff_cbs_trace_syntax_element(ctx, pos, name, subscripts, bits, value);
> +    }
> +
> +    *write_to = value;
> +    return 0;
> +}
> +
> +static int cbs_vp8_bool_decoder_read_signed(
> +    CodedBitstreamContext *ctx, CBSVP8BoolDecoder *bool_decoder, int
> width,
> +    uint8_t prob, const char *name, const int *subscripts, int32_t
> +*write_to) {
> +    int ret = 0;
> +    CodedBitstreamVP8Context *vp8 = ctx->priv_data;
> +    int32_t value;
> +    uint8_t sign = 0;
> +    int pos;
> +
> +    av_assert0(width >= 0 && width <= 8);
> +
> +    pos = vp8->uncompressed_header_size * 8;
> +    pos += cbs_vp8_bool_decoder_bit_count(bool_decoder);
> +
> +    ret = cbs_vp8_bool_decoder_read_literal(bool_decoder, prob, width,
> &value);
> +    if (ret != 0) {
> +        return ret;
> +    }
> +
> +    ret = cbs_vp8_bool_decoder_read_bool(bool_decoder, prob, &sign);
> +    if (ret != 0) {
> +        return ret;
> +    }
> +
> +    if (sign) {
> +        value = -value;
> +    }
> +
> +    if (ctx->trace_enable) {
> +        char bits[33] = "-";
> +        ff_cbs_trace_syntax_element(ctx, pos, name, subscripts, bits, value);
> +    }
> +
> +    *write_to = value;
> +    return 0;
> +}
> +
> +static int cbs_vp8_read_unsigned(CodedBitstreamContext *ctx,
> GetBitContext *gbc,
> +                                 int width, const char *name,
> +                                 const int *subscripts, uint32_t
> +*write_to) {
> +    int pos;
> +    uint32_t value;
> +
> +    av_assert0(width > 0 && width <= 24);
> +
> +    if (get_bits_left(gbc) < width) {
> +        av_log(ctx->log_ctx, AV_LOG_ERROR, "Invalid value: bitstream
> ended.\n");
> +        return AVERROR_INVALIDDATA;
> +    }
> +
> +    pos = get_bits_count(gbc);
> +    value = get_bits_le(gbc, width);
> +
> +    if (ctx->trace_enable) {
> +        int i;
> +        char bits[33];
> +        for (i = 0; i < width; i++)
> +            bits[i] = value >> (width - i - 1) & 1 ? '1' : '0';
> +        bits[i] = 0;
> +
> +        ff_cbs_trace_syntax_element(ctx, pos, name, subscripts, bits, value);
> +    }
> +
> +    *write_to = value;
> +    return 0;
> +}
> +
> +#define HEADER(name) \
> +    do { \
> +        ff_cbs_trace_header(ctx, name); \
> +    } while (0)
> +
> +#define CHECK(call) \
> +    do { \
> +        int err = (call); \
> +        if (err < 0) \
> +            return err; \
> +    } while (0)
> +
> +#define FUNC_NAME(rw, codec, name) cbs_##codec##_##rw##_##name
> #define
> +FUNC_VP8(rw, name) FUNC_NAME(rw, vp8, name) #define FUNC(name)
> +FUNC_VP8(READWRITE, name)
> +
> +#define SUBSCRIPTS(subs, ...) \
> +    (subs > 0 ? ((int[subs + 1]){subs, __VA_ARGS__}) : NULL)
> +
> +#define f(width, name) xf(width, name, 0)
> +
> +// bool [de|en]coder methods.
> +#define bc_f(width, name) bc_unsigned_subs(width, DEFAULT_PROB, true,
> +name, 0) #define bc_s(width, name) bc_signed_subs(width, DEFAULT_PROB,
> +name, 0) #define bc_fs(width, name, subs, ...) \
> +    bc_unsigned_subs(width, DEFAULT_PROB, true, name, subs,
> +__VA_ARGS__) #define bc_ss(width, name, subs, ...) \
> +    bc_signed_subs(width, DEFAULT_PROB, name, subs, __VA_ARGS__)
> +
> +// bool [de|en]coder methods for boolean value and disable tracing.
> +#define bc_b(name) bc_unsigned_subs(1, DEFAULT_PROB, false, name, 0)
> +#define bc_b_prob(prob, name) bc_unsigned_subs(1, prob, false, name, 0)
> +
> +#define READ
> +#define READWRITE read
> +#define RWContext GetBitContext
> +#define CBSVP8BoolCodingRW CBSVP8BoolDecoder
> +
> +#define xf(width, name, subs, ...) \
> +    do { \
> +        uint32_t value; \
> +        CHECK(cbs_vp8_read_unsigned(ctx, rw, width, #name, \
> +                                    SUBSCRIPTS(subs, __VA_ARGS__), &value)); \
> +        current->name = value; \
> +    } while (0)
> +
> +#define fixed(width, name, value) \
> +    do { \
> +        uint32_t fixed_value; \
> +        CHECK(ff_cbs_read_unsigned(ctx, rw, width, #name, 0, &fixed_value, \
> +                                   value, value)); \
> +    } while (0)
> +
> +#define bc_unsigned_subs(width, prob, enable_trace, name, subs, ...) \
> +    do { \
> +        uint32_t value; \
> +        CHECK(cbs_vp8_bool_decoder_read_unsigned( \
> +            ctx, bool_coding_rw, width, prob, #name, \
> +            SUBSCRIPTS(subs, __VA_ARGS__), &value, enable_trace)); \
> +        current->name = value; \
> +    } while (0)
> +
> +#define bc_signed_subs(width, prob, name, subs, ...) \
> +    do { \
> +        int32_t value; \
> +        CHECK(cbs_vp8_bool_decoder_read_signed( \
> +            ctx, bool_coding_rw, width, prob, #name, \
> +            SUBSCRIPTS(subs, __VA_ARGS__), &value)); \
> +        current->name = value; \
> +    } while (0)
> +
> +#include "cbs_vp8_syntax_template.c"
> +
> +static int cbs_vp8_split_fragment(CodedBitstreamContext *ctx,
> +                                  CodedBitstreamFragment *frag, int
> +header) {
> +    int err;
> +
> +    if (frag->data_size == 0)
> +        return AVERROR_INVALIDDATA;
> +
> +    err = ff_cbs_append_unit_data(frag, 0, frag->data, frag->data_size,
> +                                  frag->data_ref);
> +    if (err < 0)
> +        return err;
> +
> +    return 0;
> +}
> +
> +static int cbs_vp8_read_unit(CodedBitstreamContext *ctx,
> +                             CodedBitstreamUnit *unit) {
> +    CodedBitstreamVP8Context *vp8 = ctx->priv_data;
> +    VP8RawFrame *frame;
> +    GetBitContext gbc;
> +    CBSVP8BoolDecoder bool_decoder;
> +    int err, pos;
> +
> +    err = ff_cbs_alloc_unit_content(ctx, unit);
> +    if (err < 0)
> +        return err;
> +    frame = unit->content;
> +
> +    // Create GetBitContext for uncompressed header.
> +    err = init_get_bits8_le(&gbc, unit->data, 8 * unit->data_size);
> +    if (err < 0)
> +        return err;
> +
> +    err = cbs_vp8_read_uncompressed_header(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)
> +        return AVERROR_INVALIDDATA;
> +
> +    vp8->uncompressed_header_size = pos;
> +
> +    // Create bool decoder for compressed header.
> +    err = cbs_vp8_bool_decoder_init(
> +        &bool_decoder, unit->data + pos,
> +        frame->header.first_partition_length_in_bytes);
> +    if (err < 0)
> +        return err;
> +
> +    err = cbs_vp8_read_compressed_header(ctx, &bool_decoder, frame);
> +    if (err < 0)
> +        return err;
> +
> +    pos = cbs_vp8_bool_decoder_bit_count(&bool_decoder);
> +    if (pos > bool_decoder.buffer_size * 8)
> +        return AVERROR_INVALIDDATA;
> +
> +    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_vp8_write_unit(CodedBitstreamContext *ctx,
> +                              CodedBitstreamUnit *unit, PutBitContext
> +*pbc) {
> +    return AVERROR_PATCHWELCOME;
> +}
> +
> +static int cbs_vp8_assemble_fragment(CodedBitstreamContext *ctx,
> +                                     CodedBitstreamFragment *frag) {
> +    return AVERROR_PATCHWELCOME;
> +}
> +
> +static void cbs_vp8_flush(CodedBitstreamContext *ctx) {
> +    // Do nothing.
> +}
> +
> +static const CodedBitstreamUnitTypeDescriptor cbs_vp8_unit_types[] = {
> +    CBS_UNIT_TYPE_INTERNAL_REF(0, VP8RawFrame, data),
> +    CBS_UNIT_TYPE_END_OF_LIST,
> +};
> +
> +const CodedBitstreamType ff_cbs_type_vp8 = {
> +    .codec_id          = AV_CODEC_ID_VP8,
> +
> +    .priv_data_size    = sizeof(CodedBitstreamVP8Context),
> +
> +    .unit_types        = cbs_vp8_unit_types,
> +
> +    .split_fragment    = &cbs_vp8_split_fragment,
> +    .read_unit         = &cbs_vp8_read_unit,
> +    .write_unit        = &cbs_vp8_write_unit,
> +
> +    .flush             = &cbs_vp8_flush,
> +
> +    .assemble_fragment = &cbs_vp8_assemble_fragment, };
> diff --git a/libavcodec/cbs_vp8.h b/libavcodec/cbs_vp8.h new file mode
> 100644 index 0000000000..4434251c09
> --- /dev/null
> +++ b/libavcodec/cbs_vp8.h
> @@ -0,0 +1,137 @@
> +/*
> + * 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_VP8_H
> +#define AVCODEC_CBS_VP8_H
> +
> +#include <stddef.h>
> +#include <stdint.h>
> +
> +#include "cbs.h"
> +
> +enum {
> +    VP8_START_CODE_0 = 0x9D,
> +    VP8_START_CODE_1 = 0x01,
> +    VP8_START_CODE_2 = 0x2A,
> +};
> +
> +enum {
> +    VP8_KEY_FRAME = 0,
> +    VP8_NON_KEY_FRAME = 1,
> +};
> +
> +typedef struct VP8RawFrameHeader {
> +    // frame tag
> +    uint8_t frame_type;
> +    uint8_t profile;
> +    uint8_t show_frame;
> +    uint32_t first_partition_length_in_bytes;
> +
> +    uint16_t width;
> +    uint8_t horizontal_scale;
> +    uint16_t height;
> +    uint8_t vertical_scale;
> +
> +    // frame header
> +    uint8_t color_space;
> +    uint8_t clamping_type;
> +
> +    // segmentation
> +    uint8_t segmentation_enable;
> +    uint8_t update_segment_map;
> +    uint8_t update_segment_feature_data;
> +    uint8_t segment_feature_mode;
> +    uint8_t segment_qp_update[4];
> +    int8_t segment_qp[4];
> +    uint8_t segment_loop_filter_level_update[4];
> +    int8_t segment_loop_filter_level[4];
> +    uint8_t segment_probs_update[3];
> +    uint8_t segment_probs[3];
> +
> +    // loop filter
> +    uint8_t loop_filter_type;
> +    uint8_t loop_filter_level;
> +    uint8_t loop_filter_sharpness;
> +    uint8_t mode_ref_lf_delta_enable;
> +    uint8_t mode_ref_lf_delta_update;
> +    uint8_t ref_lf_deltas_update[4];
> +    int8_t ref_lf_deltas[4];
> +    uint8_t mode_lf_deltas_update[4];
> +    int8_t mode_lf_deltas[4];
> +
> +    uint8_t log2_token_partitions;
> +
> +    // qp
> +    uint8_t base_qindex;
> +    uint8_t y1dc_delta_q_present;
> +    int8_t y1dc_delta_q;
> +    uint8_t y2dc_delta_q_present;
> +    int8_t y2dc_delta_q;
> +    uint8_t y2ac_delta_q_present;
> +    int8_t y2ac_delta_q;
> +    uint8_t uvdc_delta_q_present;
> +    int8_t uvdc_delta_q;
> +    uint8_t uvac_delta_q_present;
> +    int8_t uvac_delta_q;
> +
> +    // ref
> +    uint8_t refresh_golden_frame;
> +    uint8_t refresh_alternate_frame;
> +    uint8_t copy_buffer_to_golden;
> +    uint8_t copy_buffer_to_alternate;
> +    uint8_t ref_frame_sign_bias_golden;
> +    uint8_t ref_frame_sign_bias_alternate;
> +    uint8_t refresh_last_frame;
> +
> +    uint8_t refresh_entropy_probs;
> +
> +    // token probs
> +    uint8_t coeff_prob_update[4][8][3][11];
> +    uint8_t coeff_prob[4][8][3][11];
> +
> +    uint8_t mb_no_skip_coeff;
> +    uint8_t prob_skip_false;
> +
> +    uint8_t prob_intra;
> +    uint8_t prob_last;
> +    uint8_t prob_golden;
> +
> +    uint8_t intra_16x16_prob_update;
> +    uint8_t intra_16x16_prob[4];
> +
> +    uint8_t intra_chrome_prob_update;
> +    uint8_t intra_chrome_prob[3];
> +
> +    // mv probs
> +    uint8_t mv_prob_update[2][19];
> +    uint8_t mv_prob[2][19];
> +} VP8RawFrameHeader;
> +
> +typedef struct VP8RawFrame {
> +    VP8RawFrameHeader header;
> +
> +    uint8_t *data;
> +    AVBufferRef *data_ref;
> +    size_t data_size;
> +} VP8RawFrame;
> +
> +typedef struct CodedBitstreamVP8Context {
> +    uint32_t uncompressed_header_size;
> +} CodedBitstreamVP8Context;
> +
> +#endif /* AVCODEC_CBS_VP8_H */
> diff --git a/libavcodec/cbs_vp8_syntax_template.c
> b/libavcodec/cbs_vp8_syntax_template.c
> new file mode 100644
> index 0000000000..0bdf699f39
> --- /dev/null
> +++ b/libavcodec/cbs_vp8_syntax_template.c
> @@ -0,0 +1,248 @@
> +/*
> + * 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(update_segmentation)(CodedBitstreamContext *ctx,
> +                                     CBSVP8BoolCodingRW *bool_coding_rw,
> +                                     VP8RawFrameHeader *current) {
> +    bc_f(1, update_segment_map);
> +    bc_f(1, update_segment_feature_data);
> +
> +    if (current->update_segment_feature_data) {
> +        bc_f(1, segment_feature_mode);
> +        // quantizer
> +        for (int i = 0; i < 4; i++) {
> +            bc_b(segment_qp_update[i]);
> +            if (current->segment_qp_update[i])
> +                bc_ss(7, segment_qp[i], 1, i);
> +        }
> +        // loop filter
> +        for (int i = 0; i < 4; i++) {
> +            bc_b(segment_loop_filter_level_update[i]);
> +            if (current->segment_loop_filter_level_update[i])
> +                bc_ss(6, segment_loop_filter_level[i], 1, i);
> +        }
> +    }
> +
> +    if (current->update_segment_map) {
> +        for (int i = 0; i < 3; i++) {
> +            bc_b(segment_probs_update[i]);
> +            if (current->segment_probs_update[i])
> +                bc_fs(8, segment_probs[i], 1, i);
> +        }
> +    }
> +
> +    return 0;
> +}
> +
> +static int FUNC(mode_ref_lf_deltas)(CodedBitstreamContext *ctx,
> +                                    CBSVP8BoolCodingRW *bool_coding_rw,
> +                                    VP8RawFrameHeader *current) {
> +    bc_f(1, mode_ref_lf_delta_enable);
> +    if (current->mode_ref_lf_delta_enable) {
> +        bc_b(mode_ref_lf_delta_update);
> +        if (current->mode_ref_lf_delta_update) {
> +            // ref_lf_deltas
> +            for (int i = 0; i < 4; i++) {
> +                bc_b(ref_lf_deltas_update[i]);
> +                if (current->ref_lf_deltas_update[i])
> +                    bc_ss(6, ref_lf_deltas[i], 1, i);
> +            }
> +            // mode_lf_deltas
> +            for (int i = 0; i < 4; i++) {
> +                bc_b(mode_lf_deltas_update[i]);
> +                if (current->mode_lf_deltas_update[i])
> +                    bc_ss(6, mode_lf_deltas[i], 1, i);
> +            }
> +        }
> +    }
> +
> +    return 0;
> +}
> +
> +static int FUNC(quantization_params)(CodedBitstreamContext *ctx,
> +                                     CBSVP8BoolCodingRW *bool_coding_rw,
> +                                     VP8RawFrameHeader *current) {
> +    bc_f(7, base_qindex);
> +
> +    bc_b(y1dc_delta_q_present);
> +    if (current->y1dc_delta_q_present)
> +        bc_s(4, y1dc_delta_q);
> +
> +    bc_b(y2dc_delta_q_present);
> +    if (current->y2dc_delta_q_present)
> +        bc_s(4, y2dc_delta_q);
> +
> +    bc_b(y2ac_delta_q_present);
> +    if (current->y2ac_delta_q_present)
> +        bc_s(4, y2ac_delta_q);
> +
> +    bc_b(uvdc_delta_q_present);
> +    if (current->uvdc_delta_q_present)
> +        bc_s(4, uvdc_delta_q);
> +
> +    bc_b(uvac_delta_q_present);
> +    if (current->uvac_delta_q_present)
> +        bc_s(4, uvac_delta_q);
> +
> +    return 0;
> +}
> +
> +static int FUNC(update_token_probs)(CodedBitstreamContext *ctx,
> +                                    CBSVP8BoolCodingRW *bool_coding_rw,
> +                                    VP8RawFrameHeader *current) {
> +    for (int i = 0; i < 4; ++i) {
> +        for (int j = 0; j < 8; ++j) {
> +            for (int k = 0; k < 3; ++k) {
> +                for (int l = 0; l < 11; ++l) {
> +                    bc_b_prob(vp8_token_update_probs[i][j][k][l],
> +                              coeff_prob_update[i][j][k][l]);
> +                    if (current->coeff_prob_update[i][j][k][l])
> +                        bc_fs(8, coeff_prob[i][j][k][l], 4, i, j, k, l);
> +                }
> +            }
> +        }
> +    }
> +
> +    return 0;
> +}
> +
> +static int FUNC(update_mv_probs)(CodedBitstreamContext *ctx,
> +                                 CBSVP8BoolCodingRW *bool_coding_rw,
> +                                 VP8RawFrameHeader *current) {
> +    for (int i = 0; i < 2; ++i) {
> +        for (int j = 0; j < 19; ++j) {
> +            bc_b(mv_prob_update[i][j]);
> +            if (current->mv_prob_update[i][j])
> +                bc_fs(7, mv_prob[i][j], 2, i, j);
> +        }
> +    }
> +
> +    return 0;
> +}
> +
> +static int FUNC(frame_tag)(CodedBitstreamContext *ctx, RWContext *rw,
> +                           VP8RawFrameHeader *current) {
> +    f(1, frame_type);
> +    f(3, profile);
> +    f(1, show_frame);
> +    f(19, first_partition_length_in_bytes);
> +
> +    if (current->frame_type == VP8_KEY_FRAME) {
> +        fixed(8, start_code_0, VP8_START_CODE_0);
> +        fixed(8, start_code_1, VP8_START_CODE_1);
> +        fixed(8, start_code_2, VP8_START_CODE_2);
> +
> +        f(14, width);
> +        f(2, horizontal_scale);
> +        f(14, height);
> +        f(2, vertical_scale);
> +    }
> +
> +    return 0;
> +}
> +
> +static int FUNC(frame_header)(CodedBitstreamContext *ctx,
> +                              CBSVP8BoolCodingRW *bool_coding_rw,
> +                              VP8RawFrameHeader *current) {
> +    if (current->frame_type == VP8_KEY_FRAME) {
> +        bc_f(1, color_space);
> +        bc_f(1, clamping_type);
> +    }
> +
> +    bc_f(1, segmentation_enable);
> +    if (current->segmentation_enable)
> +        CHECK(FUNC(update_segmentation)(ctx, bool_coding_rw, current));
> +
> +    bc_f(1, loop_filter_type);
> +    bc_f(6, loop_filter_level);
> +    bc_f(3, loop_filter_sharpness);
> +
> +    CHECK(FUNC(mode_ref_lf_deltas)(ctx, bool_coding_rw, current));
> +
> +    bc_f(2, log2_token_partitions);
> +
> +    CHECK(FUNC(quantization_params)(ctx, bool_coding_rw, current));
> +
> +    if (current->frame_type != VP8_KEY_FRAME) {
> +        bc_f(1, refresh_golden_frame);
> +        bc_f(1, refresh_alternate_frame);
> +        if (!current->refresh_golden_frame)
> +            bc_f(2, copy_buffer_to_golden);
> +        if (!current->refresh_alternate_frame)
> +            bc_f(2, copy_buffer_to_alternate);
> +        bc_f(1, ref_frame_sign_bias_golden);
> +        bc_f(1, ref_frame_sign_bias_alternate);
> +    }
> +    bc_f(1, refresh_entropy_probs);
> +    if (current->frame_type != VP8_KEY_FRAME)
> +        bc_f(1, refresh_last_frame);
> +
> +    CHECK(FUNC(update_token_probs)(ctx, bool_coding_rw, current));
> +
> +    bc_f(1, mb_no_skip_coeff);
> +    if (current->mb_no_skip_coeff)
> +        bc_f(8, prob_skip_false);
> +
> +    if (current->frame_type != VP8_KEY_FRAME) {
> +        bc_f(8, prob_intra);
> +        bc_f(8, prob_last);
> +        bc_f(8, prob_golden);
> +
> +        // intra_16x16_prob
> +        bc_b(intra_16x16_prob_update);
> +        if (current->intra_16x16_prob_update)
> +            for (int i = 0; i < 4; i++)
> +                bc_fs(8, intra_16x16_prob[i], 1, i);
> +
> +        // intra_chroma_prob
> +        bc_b(intra_chrome_prob_update);
> +        if (current->intra_chrome_prob_update)
> +            for (int i = 0; i < 3; i++)
> +                bc_fs(8, intra_chrome_prob[i], 1, i);
> +
> +        CHECK(FUNC(update_mv_probs)(ctx, bool_coding_rw, current));
> +    }
> +
> +    return 0;
> +}
> +
> +static int FUNC(uncompressed_header)(CodedBitstreamContext *ctx,
> RWContext *rw,
> +                                     VP8RawFrame *current) {
> +    HEADER("Frame");
> +
> +    CHECK(FUNC(frame_tag)(ctx, rw, &current->header));
> +
> +    return 0;
> +}
> +
> +static int FUNC(compressed_header)(CodedBitstreamContext *ctx,
> +                                   CBSVP8BoolCodingRW *bool_coding_rw,
> +                                   VP8RawFrame *current) {
> +    CHECK(FUNC(frame_header)(ctx, bool_coding_rw, &current->header));
> +
> +    return 0;
> +}

@Andreas Rheinhardt <andreas.rheinhardt at outlook.com>
Fixed all the commentary of PATCH v3, please take a look. Thanks.

> --
> 2.25.1
> 
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