FFmpeg/libavcodec/vp9_parser.c

/*
 * VP9 compatible video decoder
 *
 * Copyright (C) 2013 Ronald S. Bultje <rsbultje gmail com>
 * Copyright (C) 2013 Clément Bœsch <u pkh me>
 *
 * 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/intreadwrite.h"
#include "parser.h"

typedef struct VP9ParseContext {
    int n_frames; // 1-8
    int size[8];
} VP9ParseContext;

static void parse_frame(AVCodecParserContext *ctx, const uint8_t *buf, int size)
{
    if (buf[0] & 0x4) {
        ctx->pict_type = AV_PICTURE_TYPE_P;
        ctx->key_frame = 0;
    } else {
        ctx->pict_type = AV_PICTURE_TYPE_I;
        ctx->key_frame = 1;
    }
}

static int parse(AVCodecParserContext *ctx,
                 AVCodecContext *avctx,
                 const uint8_t **out_data, int *out_size,
                 const uint8_t *data, int size)
{
    VP9ParseContext *s = ctx->priv_data;
    int full_size = size;
    int marker;

    if (size <= 0) {
        *out_size = 0;
        *out_data = data;

        return 0;
    }

    if (s->n_frames > 0) {
        *out_data = data;
        *out_size = s->size[--s->n_frames];
        parse_frame(ctx, *out_data, *out_size);

        return s->n_frames > 0 ? *out_size : size /* i.e. include idx tail */;
    }

    marker = data[size - 1];
    if ((marker & 0xe0) == 0xc0) {
        int nbytes = 1 + ((marker >> 3) & 0x3);
        int n_frames = 1 + (marker & 0x7), idx_sz = 2 + n_frames * nbytes;

        if (size >= idx_sz && data[size - idx_sz] == marker) {
            const uint8_t *idx = data + size + 1 - idx_sz;
            int first = 1;

            switch (nbytes) {
#define case_n(a, rd) \
            case a: \
                while (n_frames--) { \
                    unsigned sz = rd; \
                    idx += a; \
                    if (sz > size) { \
                        s->n_frames = 0; \
                        *out_size = size; \
                        *out_data = data; \
                        av_log(avctx, AV_LOG_ERROR, \
                               "Superframe packet size too big: %u > %d\n", \
                               sz, size); \
                        return full_size; \
                    } \
                    if (first) { \
                        first = 0; \
                        *out_data = data; \
                        *out_size = sz; \
                        s->n_frames = n_frames; \
                    } else { \
                        s->size[n_frames] = sz; \
                    } \
                    data += sz; \
                    size -= sz; \
                } \
                parse_frame(ctx, *out_data, *out_size); \
                return *out_size

                case_n(1, *idx);
                case_n(2, AV_RL16(idx));
                case_n(3, AV_RL24(idx));
                case_n(4, AV_RL32(idx));
            }
        }
    }

    *out_data = data;
    *out_size = size;
    parse_frame(ctx, data, size);

    return size;
}

AVCodecParser ff_vp9_parser = {
    .codec_ids      = { AV_CODEC_ID_VP9 },
    .priv_data_size = sizeof(VP9ParseContext),
    .parser_parse   = parse,
};