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  1. /*
  2.  * RAW AC-3 and E-AC-3 demuxer
  3.  * Copyright (c) 2007 Justin Ruggles <justin.ruggles@gmail.com>
  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. #include "libavutil/crc.h"
  23. #include "libavcodec/ac3_parser.h"
  24. #include "avformat.h"
  25. #include "rawdec.h"
  26.  
  27. static int ac3_eac3_probe(AVProbeData *p, enum AVCodecID expected_codec_id)
  28. {
  29.     int max_frames, first_frames = 0, frames;
  30.     const uint8_t *buf, *buf2, *end;
  31.     AC3HeaderInfo hdr;
  32.     GetBitContext gbc;
  33.     enum AVCodecID codec_id = AV_CODEC_ID_AC3;
  34.  
  35.     max_frames = 0;
  36.     buf = p->buf;
  37.     end = buf + p->buf_size;
  38.  
  39.     for(; buf < end; buf++) {
  40.         if(buf > p->buf && !(buf[0] == 0x0B && buf[1] == 0x77)
  41.                         && !(buf[0] == 0x77 && buf[1] == 0x0B) )
  42.             continue;
  43.         buf2 = buf;
  44.  
  45.         for(frames = 0; buf2 < end; frames++) {
  46.             uint8_t buf3[4096];
  47.             int i;
  48.             if(!memcmp(buf2, "\x1\x10\0\0\0\0\0\0", 8))
  49.                 buf2+=16;
  50.             if (buf[0] == 0x77 && buf[1] == 0x0B) {
  51.                 for(i=0; i<8; i+=2) {
  52.                     buf3[i  ] = buf[i+1];
  53.                     buf3[i+1] = buf[i  ];
  54.                 }
  55.                 init_get_bits(&gbc, buf3, 54);
  56.             }else
  57.                 init_get_bits(&gbc, buf2, 54);
  58.             if(avpriv_ac3_parse_header(&gbc, &hdr) < 0)
  59.                 break;
  60.             if(buf2 + hdr.frame_size > end)
  61.                 break;
  62.             if (buf[0] == 0x77 && buf[1] == 0x0B) {
  63.                 av_assert0(hdr.frame_size <= sizeof(buf3));
  64.                 for(i=8; i<hdr.frame_size; i+=2) {
  65.                     buf3[i  ] = buf[i+1];
  66.                     buf3[i+1] = buf[i  ];
  67.                 }
  68.             }
  69.             if(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, gbc.buffer + 2, hdr.frame_size - 2))
  70.                 break;
  71.             if (hdr.bitstream_id > 10)
  72.                 codec_id = AV_CODEC_ID_EAC3;
  73.             buf2 += hdr.frame_size;
  74.         }
  75.         max_frames = FFMAX(max_frames, frames);
  76.         if(buf == p->buf)
  77.             first_frames = frames;
  78.     }
  79.     if(codec_id != expected_codec_id) return 0;
  80.     // keep this in sync with mp3 probe, both need to avoid
  81.     // issues with MPEG-files!
  82.     if   (first_frames>=4) return AVPROBE_SCORE_EXTENSION + 1;
  83.     else if(max_frames>200)return AVPROBE_SCORE_EXTENSION;
  84.     else if(max_frames>=4) return AVPROBE_SCORE_EXTENSION/2;
  85.     else if(max_frames>=1) return 1;
  86.     else                   return 0;
  87. }
  88.  
  89. #if CONFIG_AC3_DEMUXER
  90. static int ac3_probe(AVProbeData *p)
  91. {
  92.     return ac3_eac3_probe(p, AV_CODEC_ID_AC3);
  93. }
  94.  
  95. AVInputFormat ff_ac3_demuxer = {
  96.     .name           = "ac3",
  97.     .long_name      = NULL_IF_CONFIG_SMALL("raw AC-3"),
  98.     .read_probe     = ac3_probe,
  99.     .read_header    = ff_raw_audio_read_header,
  100.     .read_packet    = ff_raw_read_partial_packet,
  101.     .flags= AVFMT_GENERIC_INDEX,
  102.     .extensions = "ac3",
  103.     .raw_codec_id   = AV_CODEC_ID_AC3,
  104. };
  105. #endif
  106.  
  107. #if CONFIG_EAC3_DEMUXER
  108. static int eac3_probe(AVProbeData *p)
  109. {
  110.     return ac3_eac3_probe(p, AV_CODEC_ID_EAC3);
  111. }
  112.  
  113. AVInputFormat ff_eac3_demuxer = {
  114.     .name           = "eac3",
  115.     .long_name      = NULL_IF_CONFIG_SMALL("raw E-AC-3"),
  116.     .read_probe     = eac3_probe,
  117.     .read_header    = ff_raw_audio_read_header,
  118.     .read_packet    = ff_raw_read_partial_packet,
  119.     .flags          = AVFMT_GENERIC_INDEX,
  120.     .extensions     = "eac3",
  121.     .raw_codec_id   = AV_CODEC_ID_EAC3,
  122. };
  123. #endif
  124.