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libavcodec/mpegaudio_parser.c

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00001 /*
00002  * MPEG Audio parser
00003  * Copyright (c) 2003 Fabrice Bellard
00004  * Copyright (c) 2003 Michael Niedermayer
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 "parser.h"
00024 #include "mpegaudio.h"
00025 #include "mpegaudiodecheader.h"
00026 
00027 
00028 typedef struct MpegAudioParseContext {
00029     ParseContext pc;
00030     int frame_size;
00031     uint32_t header;
00032     int header_count;
00033 } MpegAudioParseContext;
00034 
00035 #define MPA_HEADER_SIZE 4
00036 
00037 /* header + layer + bitrate + freq + lsf/mpeg25 */
00038 #undef SAME_HEADER_MASK /* mpegaudio.h defines different version */
00039 #define SAME_HEADER_MASK \
00040    (0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19))
00041 
00042 /* useful helper to get mpeg audio stream infos. Return -1 if error in
00043    header, otherwise the coded frame size in bytes */
00044 int ff_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bit_rate)
00045 {
00046     MPADecodeHeader s1, *s = &s1;
00047 
00048     if (ff_mpa_check_header(head) != 0)
00049         return -1;
00050 
00051     if (ff_mpegaudio_decode_header(s, head) != 0) {
00052         return -1;
00053     }
00054 
00055     switch(s->layer) {
00056     case 1:
00057         avctx->codec_id = CODEC_ID_MP1;
00058         *frame_size = 384;
00059         break;
00060     case 2:
00061         avctx->codec_id = CODEC_ID_MP2;
00062         *frame_size = 1152;
00063         break;
00064     default:
00065     case 3:
00066         avctx->codec_id = CODEC_ID_MP3;
00067         if (s->lsf)
00068             *frame_size = 576;
00069         else
00070             *frame_size = 1152;
00071         break;
00072     }
00073 
00074     *sample_rate = s->sample_rate;
00075     *channels = s->nb_channels;
00076     *bit_rate = s->bit_rate;
00077     avctx->sub_id = s->layer;
00078     return s->frame_size;
00079 }
00080 
00081 static int mpegaudio_parse(AVCodecParserContext *s1,
00082                            AVCodecContext *avctx,
00083                            const uint8_t **poutbuf, int *poutbuf_size,
00084                            const uint8_t *buf, int buf_size)
00085 {
00086     MpegAudioParseContext *s = s1->priv_data;
00087     ParseContext *pc = &s->pc;
00088     uint32_t state= pc->state;
00089     int i;
00090     int next= END_NOT_FOUND;
00091 
00092     for(i=0; i<buf_size; ){
00093         if(s->frame_size){
00094             int inc= FFMIN(buf_size - i, s->frame_size);
00095             i += inc;
00096             s->frame_size -= inc;
00097 
00098             if(!s->frame_size){
00099                 next= i;
00100                 break;
00101             }
00102         }else{
00103             while(i<buf_size){
00104                 int ret, sr, channels, bit_rate, frame_size;
00105 
00106                 state= (state<<8) + buf[i++];
00107 
00108                 ret = ff_mpa_decode_header(avctx, state, &sr, &channels, &frame_size, &bit_rate);
00109                 if (ret < 4) {
00110                     s->header_count= -2;
00111                 } else {
00112                     if((state&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header)
00113                         s->header_count= -3;
00114                     s->header= state;
00115                     s->header_count++;
00116                     s->frame_size = ret-4;
00117 
00118                     if(s->header_count > 1){
00119                         avctx->sample_rate= sr;
00120                         avctx->channels   = channels;
00121                         avctx->frame_size = frame_size;
00122                         avctx->bit_rate   = bit_rate;
00123                     }
00124                     break;
00125                 }
00126             }
00127         }
00128     }
00129 
00130     pc->state= state;
00131     if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) {
00132         *poutbuf = NULL;
00133         *poutbuf_size = 0;
00134         return buf_size;
00135     }
00136 
00137     *poutbuf = buf;
00138     *poutbuf_size = buf_size;
00139     return next;
00140 }
00141 
00142 
00143 AVCodecParser mpegaudio_parser = {
00144     { CODEC_ID_MP1, CODEC_ID_MP2, CODEC_ID_MP3 },
00145     sizeof(MpegAudioParseContext),
00146     NULL,
00147     mpegaudio_parse,
00148     ff_parse_close,
00149 };

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