/* * MPEG Audio parser * Copyright (c) 2003 Fabrice Bellard * Copyright (c) 2003 Michael Niedermayer * * This file is part of FFmpeg. * * FFmpeg is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 2.1 of the License, or (at your option) any later version. * * FFmpeg is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with FFmpeg; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA */ #include "parser.h" #include "mpegaudio.h" #include "mpegaudiodecheader.h" typedef struct MpegAudioParseContext { ParseContext pc; int frame_size; uint32_t header; int header_count; } MpegAudioParseContext; #define MPA_HEADER_SIZE 4 /* header + layer + bitrate + freq + lsf/mpeg25 */ #undef SAME_HEADER_MASK /* mpegaudio.h defines different version */ #define SAME_HEADER_MASK \ (0xffe00000 | (3 << 17) | (3 << 10) | (3 << 19)) /* useful helper to get mpeg audio stream infos. Return -1 if error in header, otherwise the coded frame size in bytes */ int ff_mpa_decode_header(AVCodecContext *avctx, uint32_t head, int *sample_rate, int *channels, int *frame_size, int *bit_rate) { MPADecodeHeader s1, *s = &s1; if (ff_mpa_check_header(head) != 0) return -1; if (ff_mpegaudio_decode_header(s, head) != 0) { return -1; } switch(s->layer) { case 1: avctx->codec_id = CODEC_ID_MP1; *frame_size = 384; break; case 2: avctx->codec_id = CODEC_ID_MP2; *frame_size = 1152; break; default: case 3: avctx->codec_id = CODEC_ID_MP3; if (s->lsf) *frame_size = 576; else *frame_size = 1152; break; } *sample_rate = s->sample_rate; *channels = s->nb_channels; *bit_rate = s->bit_rate; avctx->sub_id = s->layer; return s->frame_size; } static int mpegaudio_parse(AVCodecParserContext *s1, AVCodecContext *avctx, const uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size) { MpegAudioParseContext *s = s1->priv_data; ParseContext *pc = &s->pc; uint32_t state= pc->state; int i; int next= END_NOT_FOUND; for(i=0; i<buf_size; ){ if(s->frame_size){ int inc= FFMIN(buf_size - i, s->frame_size); i += inc; s->frame_size -= inc; if(!s->frame_size){ next= i; break; } }else{ while(i<buf_size){ int ret, sr, channels, bit_rate, frame_size; state= (state<<8) + buf[i++]; ret = ff_mpa_decode_header(avctx, state, &sr, &channels, &frame_size, &bit_rate); if (ret < 4) { s->header_count= -2; } else { if((state&SAME_HEADER_MASK) != (s->header&SAME_HEADER_MASK) && s->header) s->header_count= -3; s->header= state; s->header_count++; s->frame_size = ret-4; if(s->header_count > 1){ avctx->sample_rate= sr; avctx->channels = channels; avctx->frame_size = frame_size; avctx->bit_rate = bit_rate; } break; } } } } pc->state= state; if (ff_combine_frame(pc, next, &buf, &buf_size) < 0) { *poutbuf = NULL; *poutbuf_size = 0; return buf_size; } *poutbuf = buf; *poutbuf_size = buf_size; return next; } AVCodecParser mpegaudio_parser = { { CODEC_ID_MP1, CODEC_ID_MP2, CODEC_ID_MP3 }, sizeof(MpegAudioParseContext), NULL, mpegaudio_parse, ff_parse_close, };