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 "config_components.h"
  23
  24 #include "libavutil/avassert.h"
  25 #include "libavutil/crc.h"
  26 #include "libavcodec/ac3_parser.h"
  27 #include "avformat.h"
  28 #include "demux.h"
  29 #include "rawdec.h"
  30
  31 static int ac3_eac3_probe(const AVProbeData *p, enum AVCodecID expected_codec_id)
  32 {
  33     int max_frames, first_frames = 0, frames;
  34     const uint8_t *buf, *buf2, *end;
  35     enum AVCodecID codec_id = AV_CODEC_ID_AC3;
  36
  37     max_frames = 0;
  38     buf = p->buf;
  39     end = buf + p->buf_size;
  40
  41     for(; buf < end; buf++) {
  42         if(buf > p->buf && !(buf[0] == 0x0B && buf[1] == 0x77)
  43                         && !(buf[0] == 0x77 && buf[1] == 0x0B) )
  44             continue;
  45         buf2 = buf;
  46
  47         for(frames = 0; buf2 < end; frames++) {
  48             uint8_t buf3[4096];
  49             uint8_t bitstream_id;
  50             uint16_t frame_size;
  51             int i, ret;
  52
  53             if(!memcmp(buf2, "\x1\x10", 2)) {
  54                 if (buf2 + 16 > end)
  55                     break;
  56                 buf2+=16;
  57             }
  58             if (buf[0] == 0x77 && buf[1] == 0x0B) {
  59                 for(i=0; i<8; i+=2) {
  60                     buf3[i  ] = buf2[i+1];
  61                     buf3[i+1] = buf2[i  ];
  62                 }
  63                 ret = av_ac3_parse_header(buf3, 8, &bitstream_id,
  64                                           &frame_size);
  65             }else
  66                 ret = av_ac3_parse_header(buf2, end - buf2, &bitstream_id,
  67                                           &frame_size);
  68             if (ret < 0)
  69                 break;
  70             if(buf2 + frame_size > end)
  71                 break;
  72             if (buf[0] == 0x77 && buf[1] == 0x0B) {
  73                 av_assert0(frame_size <= sizeof(buf3));
  74                 for(i = 8; i < frame_size; i += 2) {
  75                     buf3[i  ] = buf2[i+1];
  76                     buf3[i+1] = buf2[i  ];
  77                 }
  78                 if (av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf3 + 2, frame_size - 2))
  79                     break;
  80             } else {
  81                 if (av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, buf2 + 2, frame_size - 2))
  82                     break;
  83             }
  84             if (bitstream_id > 10)
  85                 codec_id = AV_CODEC_ID_EAC3;
  86             buf2 += frame_size;
  87         }
  88         max_frames = FFMAX(max_frames, frames);
  89         if(buf == p->buf)
  90             first_frames = frames;
  91     }
  92     if(codec_id != expected_codec_id) return 0;
  93     // keep this in sync with mp3 probe, both need to avoid
  94     // issues with MPEG-files!
  95     if   (first_frames>=7) return AVPROBE_SCORE_EXTENSION + 1;
  96     else if(max_frames>200)return AVPROBE_SCORE_EXTENSION;
  97     else if(max_frames>=4) return AVPROBE_SCORE_EXTENSION/2;
  98     else if(max_frames>=1) return 1;
  99     else                   return 0;
 100 }
 101
 102 #if CONFIG_AC3_DEMUXER
 103 static int ac3_probe(const AVProbeData *p)
 104 {
 105     return ac3_eac3_probe(p, AV_CODEC_ID_AC3);
 106 }
 107
 108 const FFInputFormat ff_ac3_demuxer = {
 109     .p.name         = "ac3",
 110     .p.long_name    = NULL_IF_CONFIG_SMALL("raw AC-3"),
 111     .p.flags        = AVFMT_GENERIC_INDEX,
 112     .p.extensions   = "ac3",
 113     .p.priv_class   = &ff_raw_demuxer_class,
 114     .read_probe     = ac3_probe,
 115     .read_header    = ff_raw_audio_read_header,
 116     .read_packet    = ff_raw_read_partial_packet,
 117     .raw_codec_id   = AV_CODEC_ID_AC3,
 118     .priv_data_size = sizeof(FFRawDemuxerContext),
 119 };
 120 #endif
 121
 122 #if CONFIG_EAC3_DEMUXER
 123 static int eac3_probe(const AVProbeData *p)
 124 {
 125     return ac3_eac3_probe(p, AV_CODEC_ID_EAC3);
 126 }
 127
 128 const FFInputFormat ff_eac3_demuxer = {
 129     .p.name         = "eac3",
 130     .p.long_name    = NULL_IF_CONFIG_SMALL("raw E-AC-3"),
 131     .p.flags        = AVFMT_GENERIC_INDEX,
 132     .p.extensions   = "eac3,ec3",
 133     .p.priv_class   = &ff_raw_demuxer_class,
 134     .read_probe     = eac3_probe,
 135     .read_header    = ff_raw_audio_read_header,
 136     .read_packet    = ff_raw_read_partial_packet,
 137     .raw_codec_id   = AV_CODEC_ID_EAC3,
 138     .priv_data_size = sizeof(FFRawDemuxerContext),
 139 };
 140 #endif