libavformat/ac3dec.c

   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/avassert.h"
  23 #include "libavutil/crc.h"
  24 #include "libavcodec/ac3_parser.h"
  25 #include "avformat.h"
  26 #include "rawdec.h"
  27
  28 static int ac3_eac3_probe(const AVProbeData *p, enum AVCodecID expected_codec_id)
  29 {
  30     int max_frames, first_frames = 0, frames;
  31     const uint8_t *buf, *buf2, *end;
  32     enum AVCodecID codec_id = AV_CODEC_ID_AC3;
  33
  34     max_frames = 0;
  35     buf = p->buf;
  36     end = buf + p->buf_size;
  37
  38     for(; buf < end; buf++) {
  39         if(buf > p->buf && !(buf[0] == 0x0B && buf[1] == 0x77)
  40                         && !(buf[0] == 0x77 && buf[1] == 0x0B) )
  41             continue;
  42         buf2 = buf;
  43
  44         for(frames = 0; buf2 < end; frames++) {
  45             uint8_t buf3[4096];
  46             uint8_t bitstream_id;
  47             uint16_t frame_size;
  48             int i, ret;
  49
  50             if(!memcmp(buf2, "\x1\x10", 2)) {
  51                 if (buf2 + 16 > end)
  52                     break;
  53                 buf2+=16;
  54             }
  55             if (buf[0] == 0x77 && buf[1] == 0x0B) {
  56                 for(i=0; i<8; i+=2) {
  57                     buf3[i  ] = buf2[i+1];
  58                     buf3[i+1] = buf2[i  ];
  59                 }
  60                 ret = av_ac3_parse_header(buf3, 8, &bitstream_id,
  61                                           &frame_size);
  62             }else
  63                 ret = av_ac3_parse_header(buf2, end - buf2, &bitstream_id,
  64                                           &frame_size);
  65             if (ret < 0)
  66                 break;
  67             if(buf2 + frame_size > end)
  68                 break;
  69             if (buf[0] == 0x77 && buf[1] == 0x0B) {
  70                 av_assert0(frame_size <= sizeof(buf3));
  71                 for(i = 8; i < frame_size; i += 2) {
  72                     buf3[i  ] = buf2[i+1];
  73                     buf3[i+1] = buf2[i  ];
  74                 }
  75                 if (av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf3 + 2, frame_size - 2))
  76                     break;
  77             } else {
  78                 if (av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf2 + 2, frame_size - 2))
  79                     break;
  80             }
  81             if (bitstream_id > 10)
  82                 codec_id = AV_CODEC_ID_EAC3;
  83             buf2 += frame_size;
  84         }
  85         max_frames = FFMAX(max_frames, frames);
  86         if(buf == p->buf)
  87             first_frames = frames;
  88     }
  89     if(codec_id != expected_codec_id) return 0;
  90     // keep this in sync with mp3 probe, both need to avoid
  91     // issues with MPEG-files!
  92     if   (first_frames>=7) return AVPROBE_SCORE_EXTENSION + 1;
  93     else if(max_frames>200)return AVPROBE_SCORE_EXTENSION;
  94     else if(max_frames>=4) return AVPROBE_SCORE_EXTENSION/2;
  95     else if(max_frames>=1) return 1;
  96     else                   return 0;
  97 }
  98
  99 #if CONFIG_AC3_DEMUXER
 100 static int ac3_probe(const AVProbeData *p)
 101 {
 102     return ac3_eac3_probe(p, AV_CODEC_ID_AC3);
 103 }
 104
 105 FF_RAW_DEMUXER_CLASS(ac3)
 106 AVInputFormat ff_ac3_demuxer = {
 107     .name           = "ac3",
 108     .long_name      = NULL_IF_CONFIG_SMALL("raw AC-3"),
 109     .read_probe     = ac3_probe,
 110     .read_header    = ff_raw_audio_read_header,
 111     .read_packet    = ff_raw_read_partial_packet,
 112     .flags= AVFMT_GENERIC_INDEX,
 113     .extensions = "ac3",
 114     .raw_codec_id   = AV_CODEC_ID_AC3,
 115     .priv_data_size = sizeof(FFRawDemuxerContext),
 116     .priv_class     = &ac3_demuxer_class,
 117 };
 118 #endif
 119
 120 #if CONFIG_EAC3_DEMUXER
 121 static int eac3_probe(const AVProbeData *p)
 122 {
 123     return ac3_eac3_probe(p, AV_CODEC_ID_EAC3);
 124 }
 125
 126 FF_RAW_DEMUXER_CLASS(eac3)
 127 AVInputFormat ff_eac3_demuxer = {
 128     .name           = "eac3",
 129     .long_name      = NULL_IF_CONFIG_SMALL("raw E-AC-3"),
 130     .read_probe     = eac3_probe,
 131     .read_header    = ff_raw_audio_read_header,
 132     .read_packet    = ff_raw_read_partial_packet,
 133     .flags          = AVFMT_GENERIC_INDEX,
 134     .extensions     = "eac3",
 135     .raw_codec_id   = AV_CODEC_ID_EAC3,
 136     .priv_data_size = sizeof(FFRawDemuxerContext),
 137     .priv_class     = &eac3_demuxer_class,
 138 };
 139 #endif