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libavformat/aacdec.c

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00001 /*
00002  * raw ADTS AAC demuxer
00003  * Copyright (c) 2008 Michael Niedermayer <michaelni@gmx.at>
00004  * Copyright (c) 2009 Robert Swain ( rob opendot cl )
00005  *
00006  * This file is part of FFmpeg.
00007  *
00008  * FFmpeg is free software; you can redistribute it and/or
00009  * modify it under the terms of the GNU Lesser General Public
00010  * License as published by the Free Software Foundation; either
00011  * version 2.1 of the License, or (at your option) any later version.
00012  *
00013  * FFmpeg is distributed in the hope that it will be useful,
00014  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00015  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00016  * Lesser General Public License for more details.
00017  *
00018  * You should have received a copy of the GNU Lesser General Public
00019  * License along with FFmpeg; if not, write to the Free Software
00020  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00021  */
00022 
00023 #include "libavutil/intreadwrite.h"
00024 #include "avformat.h"
00025 #include "rawdec.h"
00026 #include "id3v1.h"
00027 
00028 
00029 static int adts_aac_probe(AVProbeData *p)
00030 {
00031     int max_frames = 0, first_frames = 0;
00032     int fsize, frames;
00033     uint8_t *buf0 = p->buf;
00034     uint8_t *buf2;
00035     uint8_t *buf;
00036     uint8_t *end = buf0 + p->buf_size - 7;
00037 
00038     buf = buf0;
00039 
00040     for(; buf < end; buf= buf2+1) {
00041         buf2 = buf;
00042 
00043         for(frames = 0; buf2 < end; frames++) {
00044             uint32_t header = AV_RB16(buf2);
00045             if((header&0xFFF6) != 0xFFF0)
00046                 break;
00047             fsize = (AV_RB32(buf2 + 3) >> 13) & 0x1FFF;
00048             if(fsize < 7)
00049                 break;
00050             buf2 += fsize;
00051         }
00052         max_frames = FFMAX(max_frames, frames);
00053         if(buf == buf0)
00054             first_frames= frames;
00055     }
00056     if   (first_frames>=3) return AVPROBE_SCORE_MAX/2+1;
00057     else if(max_frames>500)return AVPROBE_SCORE_MAX/2;
00058     else if(max_frames>=3) return AVPROBE_SCORE_MAX/4;
00059     else if(max_frames>=1) return 1;
00060     else                   return 0;
00061 }
00062 
00063 static int adts_aac_read_header(AVFormatContext *s,
00064                                 AVFormatParameters *ap)
00065 {
00066     AVStream *st;
00067 
00068     st = av_new_stream(s, 0);
00069     if (!st)
00070         return AVERROR(ENOMEM);
00071 
00072     st->codec->codec_type = AVMEDIA_TYPE_AUDIO;
00073     st->codec->codec_id = s->iformat->value;
00074     st->need_parsing = AVSTREAM_PARSE_FULL;
00075 
00076     ff_id3v1_read(s);
00077 
00078     //LCM of all possible ADTS sample rates
00079     av_set_pts_info(st, 64, 1, 28224000);
00080 
00081     return 0;
00082 }
00083 
00084 AVInputFormat ff_aac_demuxer = {
00085     "aac",
00086     NULL_IF_CONFIG_SMALL("raw ADTS AAC"),
00087     0,
00088     adts_aac_probe,
00089     adts_aac_read_header,
00090     ff_raw_read_partial_packet,
00091     .flags= AVFMT_GENERIC_INDEX,
00092     .extensions = "aac",
00093     .value = CODEC_ID_AAC,
00094 };

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