1/* 2 * MPEG Audio parser 3 * Copyright (c) 2003 Fabrice Bellard 4 * Copyright (c) 2003 Michael Niedermayer 5 * 6 * This file is part of FFmpeg. 7 * 8 * FFmpeg is free software; you can redistribute it and/or 9 * modify it under the terms of the GNU Lesser General Public 10 * License as published by the Free Software Foundation; either 11 * version 2.1 of the License, or (at your option) any later version. 12 * 13 * FFmpeg is distributed in the hope that it will be useful, 14 * but WITHOUT ANY WARRANTY; without even the implied warranty of 15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 16 * Lesser General Public License for more details. 17 * 18 * You should have received a copy of the GNU Lesser General Public 19 * License along with FFmpeg; if not, write to the Free Software 20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 21 */ 22 23#include "parser.h" 24#include "mpegaudiodecheader.h" 25#include "libavutil/common.h" 26 27 28typedef struct MpegAudioParseContext { 29 ParseContext pc; 30 int frame_size; 31 uint32_t header; 32 int header_count; 33 int no_bitrate; 34} MpegAudioParseContext; 35 36#define MPA_HEADER_SIZE 4 37 38/* header + layer + bitrate + freq + lsf/mpeg25 */ 39#define SAME_HEADER_MASK \ 40 (0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19)) 41 42static int mpegaudio_parse(AVCodecParserContext *s1, 43 AVCodecContext *avctx, 44 const uint8_t **poutbuf, int *poutbuf_size, 45 const uint8_t *buf, int buf_size) 46{ 47 MpegAudioParseContext *s = s1->priv_data; 48 ParseContext *pc = &s->pc; 49 uint32_t state= pc->state; 50 int i; 51 int next= END_NOT_FOUND; 52 53 for(i=0; i<buf_size; ){ 54 if(s->frame_size){ 55 int inc= FFMIN(buf_size - i, s->frame_size); 56 i += inc; 57 s->frame_size -= inc; 58 state = 0; 59 60 if(!s->frame_size){ 61 next= i; 62 break; 63 } 64 }else{ 65 while(i<buf_size){ 66 int ret, sr, channels, bit_rate, frame_size; 67 enum AVCodecID codec_id; 68 69 state= (state<<8) + buf[i++]; 70 71 ret = avpriv_mpa_decode_header2(state, &sr, &channels, &frame_size, &bit_rate, &codec_id); 72 if (ret < 4) { 73 if (i > 4) 74 s->header_count = -2; 75 } else { 76 if((state&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header) 77 s->header_count= -3; 78 s->header= state; 79 s->header_count++; 80 s->frame_size = ret-4; 81 82 if (s->header_count > 0 + (avctx->codec_id != AV_CODEC_ID_NONE && avctx->codec_id != codec_id)) { 83 avctx->sample_rate= sr; 84 avctx->channels = channels; 85 s1->duration = frame_size; 86 avctx->codec_id = codec_id; 87 if (s->no_bitrate || !avctx->bit_rate) { 88 s->no_bitrate = 1; 89 avctx->bit_rate += (bit_rate - avctx->bit_rate) / s->header_count; 90 } 91 } 92 break; 93 } 94 } 95 } 96 } 97 98 pc->state= state; 99 if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) { 100 *poutbuf = NULL; 101 *poutbuf_size = 0; 102 return buf_size; 103 } 104 105 *poutbuf = buf; 106 *poutbuf_size = buf_size; 107 return next; 108} 109 110 111AVCodecParser ff_mpegaudio_parser = { 112 .codec_ids = { AV_CODEC_ID_MP1, AV_CODEC_ID_MP2, AV_CODEC_ID_MP3 }, 113 .priv_data_size = sizeof(MpegAudioParseContext), 114 .parser_parse = mpegaudio_parse, 115 .parser_close = ff_parse_close, 116}; 117