libavcodec/cri_parser.c

   1 /*
   2  * CRI parser
   3  * Copyright (c) 2021 Paul B Mahol
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file
  24  * CRI parser
  25  */
  26
  27 #include "libavutil/bswap.h"
  28 #include "libavutil/common.h"
  29
  30 #include "parser.h"
  31
  32 typedef struct CRIParser {
  33     ParseContext pc;
  34     int count;
  35     int chunk;
  36     int read_bytes;
  37     int skip_bytes;
  38 } CRIParser;
  39
  40 #define KEY (((uint64_t)'\1' << 56) | ((uint64_t)'\0' << 48) | \
  41              ((uint64_t)'\0' << 40) | ((uint64_t)'\0' << 32) | \
  42              ((uint64_t)'\4' << 24) | ((uint64_t)'\0' << 16) | \
  43              ((uint64_t)'\0' <<  8) | ((uint64_t)'\0' <<  0))
  44
  45 static int cri_parse(AVCodecParserContext *s, AVCodecContext *avctx,
  46                      const uint8_t **poutbuf, int *poutbuf_size,
  47                      const uint8_t *buf, int buf_size)
  48 {
  49     CRIParser *bpc = s->priv_data;
  50     uint64_t state = bpc->pc.state64;
  51     int next = END_NOT_FOUND, i = 0;
  52
  53     s->pict_type = AV_PICTURE_TYPE_I;
  54     s->key_frame = 1;
  55     s->duration  = 1;
  56
  57     *poutbuf_size = 0;
  58     *poutbuf = NULL;
  59
  60     for (; i < buf_size; i++) {
  61         state = (state << 8) | buf[i];
  62         bpc->read_bytes++;
  63
  64         if (bpc->skip_bytes > 0) {
  65             bpc->skip_bytes--;
  66             if (bpc->skip_bytes == 0)
  67                 bpc->read_bytes = 0;
  68         } else {
  69             if (state != KEY)
  70                 continue;
  71         }
  72
  73         if (bpc->skip_bytes == 0 && bpc->read_bytes >= 8) {
  74             bpc->skip_bytes = av_bswap32(state & 0xFFFFFFFF);
  75             bpc->chunk = state >> 32;
  76             bpc->read_bytes = 0;
  77             bpc->count++;
  78         }
  79
  80         if (bpc->chunk == 0x01000000 && bpc->skip_bytes == 4 &&
  81             bpc->read_bytes == 0 && bpc->count > 1) {
  82             next = i - 7;
  83             break;
  84         }
  85     }
  86
  87     bpc->pc.state64 = state;
  88     if (ff_combine_frame(&bpc->pc, next, &buf, &buf_size) < 0) {
  89         *poutbuf = NULL;
  90         *poutbuf_size = 0;
  91         return buf_size;
  92     }
  93
  94     *poutbuf      = buf;
  95     *poutbuf_size = buf_size;
  96
  97     return next;
  98 }
  99
 100 const AVCodecParser ff_cri_parser = {
 101     .codec_ids      = { AV_CODEC_ID_CRI },
 102     .priv_data_size = sizeof(CRIParser),
 103     .parser_parse   = cri_parse,
 104     .parser_close   = ff_parse_close,
 105 };