libavcodec/dirac_parser.c

   1 /*
   2  * Dirac parser
   3  *
   4  * Copyright (c) 2007 Marco Gerards <marco@gnu.org>
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 /**
  24  * @file dirac_parser.c
  25  * Dirac Parser
  26  * @author Marco Gerards <marco@gnu.org>
  27  */
  28
  29 #include "parser.h"
  30
  31 #define DIRAC_PARSE_INFO_PREFIX 0x42424344
  32
  33 /**
  34  * Finds the end of the current frame in the bitstream.
  35  * @return the position of the first byte of the next frame or -1
  36  */
  37 static int find_frame_end(ParseContext *pc, const uint8_t *buf, int buf_size)
  38 {
  39     uint32_t state = pc->state;
  40     int i;
  41
  42     for (i = 0; i < buf_size; i++) {
  43         state = (state << 8) | buf[i];
  44         if (state == DIRAC_PARSE_INFO_PREFIX) {
  45             pc->frame_start_found ^= 1;
  46             if (!pc->frame_start_found) {
  47                 pc->state = -1;
  48                 return i - 3;
  49             }
  50         }
  51     }
  52
  53     pc->state = state;
  54
  55     return END_NOT_FOUND;
  56 }
  57
  58 static int dirac_parse(AVCodecParserContext *s, AVCodecContext *avctx,
  59                        const uint8_t **poutbuf, int *poutbuf_size,
  60                        const uint8_t *buf, int buf_size)
  61 {
  62     ParseContext *pc = s->priv_data;
  63     int next;
  64
  65     if (s->flags & PARSER_FLAG_COMPLETE_FRAMES) {
  66         next = buf_size;
  67     }else{
  68         next = find_frame_end(pc, buf, buf_size);
  69
  70         if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
  71             *poutbuf = NULL;
  72             *poutbuf_size = 0;
  73             return buf_size;
  74         }
  75     }
  76
  77     *poutbuf = buf;
  78     *poutbuf_size = buf_size;
  79     return next;
  80 }
  81
  82 AVCodecParser dirac_parser = {
  83     { CODEC_ID_DIRAC },
  84     sizeof(ParseContext),
  85     NULL,
  86     dirac_parse,
  87     ff_parse_close,
  88 };