[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 05:39:33 EEST 2023


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;
+}
-- 
2.25.1



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