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libavcodec/mp3_header_decompress_bsf.c

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00001 /*
00002  * copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
00003  *
00004  * This file is part of FFmpeg.
00005  *
00006  * FFmpeg is free software; you can redistribute it and/or
00007  * modify it under the terms of the GNU Lesser General Public
00008  * License as published by the Free Software Foundation; either
00009  * version 2.1 of the License, or (at your option) any later version.
00010  *
00011  * FFmpeg is distributed in the hope that it will be useful,
00012  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00013  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00014  * Lesser General Public License for more details.
00015  *
00016  * You should have received a copy of the GNU Lesser General Public
00017  * License along with FFmpeg; if not, write to the Free Software
00018  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00019  */
00020 
00021 #include "avcodec.h"
00022 #include "mpegaudio.h"
00023 #include "mpegaudiodata.h"
00024 
00025 
00026 static int mp3_header_decompress(AVBitStreamFilterContext *bsfc, AVCodecContext *avctx, const char *args,
00027                      uint8_t **poutbuf, int *poutbuf_size,
00028                      const uint8_t *buf, int buf_size, int keyframe){
00029     uint32_t header;
00030     int sample_rate= avctx->sample_rate;
00031     int sample_rate_index=0;
00032     int lsf, mpeg25, bitrate_index, frame_size;
00033 
00034     header = AV_RB32(buf);
00035     if(ff_mpa_check_header(header) >= 0){
00036         *poutbuf= (uint8_t *) buf;
00037         *poutbuf_size= buf_size;
00038 
00039         return 0;
00040     }
00041 
00042     if(avctx->extradata_size != 15 || strcmp(avctx->extradata, "FFCMP3 0.0")){
00043         av_log(avctx, AV_LOG_ERROR, "Extradata invalid %d\n", avctx->extradata_size);
00044         return -1;
00045     }
00046 
00047     header= AV_RB32(avctx->extradata+11) & MP3_MASK;
00048 
00049     lsf     = sample_rate < (24000+32000)/2;
00050     mpeg25  = sample_rate < (12000+16000)/2;
00051     sample_rate_index= (header>>10)&3;
00052     sample_rate= ff_mpa_freq_tab[sample_rate_index] >> (lsf + mpeg25); //in case sample rate is a little off
00053 
00054     for(bitrate_index=2; bitrate_index<30; bitrate_index++){
00055         frame_size = ff_mpa_bitrate_tab[lsf][2][bitrate_index>>1];
00056         frame_size = (frame_size * 144000) / (sample_rate << lsf) + (bitrate_index&1);
00057         if(frame_size == buf_size + 4)
00058             break;
00059         if(frame_size == buf_size + 6)
00060             break;
00061     }
00062     if(bitrate_index == 30){
00063         av_log(avctx, AV_LOG_ERROR, "Could not find bitrate_index.\n");
00064         return -1;
00065     }
00066 
00067     header |= (bitrate_index&1)<<9;
00068     header |= (bitrate_index>>1)<<12;
00069     header |= (frame_size == buf_size + 4)<<16; //FIXME actually set a correct crc instead of 0
00070 
00071     *poutbuf_size= frame_size;
00072     *poutbuf= av_malloc(frame_size + FF_INPUT_BUFFER_PADDING_SIZE);
00073     memcpy(*poutbuf + frame_size - buf_size, buf, buf_size + FF_INPUT_BUFFER_PADDING_SIZE);
00074 
00075     if(avctx->channels==2){
00076         uint8_t *p= *poutbuf + frame_size - buf_size;
00077         if(lsf){
00078             FFSWAP(int, p[1], p[2]);
00079             header |= (p[1] & 0xC0)>>2;
00080             p[1] &= 0x3F;
00081         }else{
00082             header |= p[1] & 0x30;
00083             p[1] &= 0xCF;
00084         }
00085     }
00086 
00087     AV_WB32(*poutbuf, header);
00088 
00089     return 1;
00090 }
00091 
00092 AVBitStreamFilter mp3_header_decompress_bsf={
00093     "mp3decomp",
00094     0,
00095     mp3_header_decompress,
00096 };

Generated on Fri Sep 16 2011 17:17:39 for FFmpeg by  doxygen 1.7.1