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 "mpegaudio.h" 25#include "mpegaudiodecheader.h" 26 27 28typedef struct MpegAudioParseContext { 29 ParseContext pc; 30 int frame_size; 31 uint32_t header; 32 int header_count; 33} MpegAudioParseContext; 34 35#define MPA_HEADER_SIZE 4 36 37/* header + layer + bitrate + freq + lsf/mpeg25 */ 38#undef SAME_HEADER_MASK /* mpegaudio.h defines different version */ 39#define SAME_HEADER_MASK \ 40 (0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19)) 41 42/* useful helper to get mpeg audio stream infos. Return -1 if error in 43 header, otherwise the coded frame size in bytes */ 44int ff_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bit_rate) 45{ 46 MPADecodeHeader s1, *s = &s1; 47 48 if (ff_mpa_check_header(head) != 0) 49 return -1; 50 51 if (ff_mpegaudio_decode_header(s, head) != 0) { 52 return -1; 53 } 54 55 switch(s->layer) { 56 case 1: 57 avctx->codec_id = CODEC_ID_MP1; 58 *frame_size = 384; 59 break; 60 case 2: 61 avctx->codec_id = CODEC_ID_MP2; 62 *frame_size = 1152; 63 break; 64 default: 65 case 3: 66 avctx->codec_id = CODEC_ID_MP3; 67 if (s->lsf) 68 *frame_size = 576; 69 else 70 *frame_size = 1152; 71 break; 72 } 73 74 *sample_rate = s->sample_rate; 75 *channels = s->nb_channels; 76 *bit_rate = s->bit_rate; 77 avctx->sub_id = s->layer; 78 return s->frame_size; 79} 80 81static int mpegaudio_parse(AVCodecParserContext *s1, 82 AVCodecContext *avctx, 83 const uint8_t **poutbuf, int *poutbuf_size, 84 const uint8_t *buf, int buf_size) 85{ 86 MpegAudioParseContext *s = s1->priv_data; 87 ParseContext *pc = &s->pc; 88 uint32_t state= pc->state; 89 int i; 90 int next= END_NOT_FOUND; 91 92 for(i=0; i<buf_size; ){ 93 if(s->frame_size){ 94 int inc= FFMIN(buf_size - i, s->frame_size); 95 i += inc; 96 s->frame_size -= inc; 97 98 if(!s->frame_size){ 99 next= i; 100 break; 101 } 102 }else{ 103 while(i<buf_size){ 104 int ret, sr, channels, bit_rate, frame_size; 105 106 state= (state<<8) + buf[i++]; 107 108 ret = ff_mpa_decode_header(avctx, state, &sr, &channels, &frame_size, &bit_rate); 109 if (ret < 4) { 110 s->header_count= -2; 111 } else { 112 if((state&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header) 113 s->header_count= -3; 114 s->header= state; 115 s->header_count++; 116 s->frame_size = ret-4; 117 118 if(s->header_count > 1){ 119 avctx->sample_rate= sr; 120 avctx->channels = channels; 121 avctx->frame_size = frame_size; 122 avctx->bit_rate = bit_rate; 123 } 124 break; 125 } 126 } 127 } 128 } 129 130 pc->state= state; 131 if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) { 132 *poutbuf = NULL; 133 *poutbuf_size = 0; 134 return buf_size; 135 } 136 137 *poutbuf = buf; 138 *poutbuf_size = buf_size; 139 return next; 140} 141 142 143AVCodecParser mpegaudio_parser = { 144 { CODEC_ID_MP1, CODEC_ID_MP2, CODEC_ID_MP3 }, 145 sizeof(MpegAudioParseContext), 146 NULL, 147 mpegaudio_parse, 148 ff_parse_close, 149}; 150