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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 "libavutil/intreadwrite.h"
00022 #include "avcodec.h"
00023 #include "mpegaudiodecheader.h"
00024 #include "mpegaudiodata.h"
00025 
00026 
00027 static int mp3_header_decompress(AVBitStreamFilterContext *bsfc, AVCodecContext *avctx, const char *args,
00028                      uint8_t **poutbuf, int *poutbuf_size,
00029                      const uint8_t *buf, int buf_size, int keyframe){
00030     uint32_t header;
00031     int sample_rate= avctx->sample_rate;
00032     int sample_rate_index=0;
00033     int lsf, mpeg25, bitrate_index, frame_size;
00034 
00035     header = AV_RB32(buf);
00036     if(ff_mpa_check_header(header) >= 0){
00037         *poutbuf= (uint8_t *) buf;
00038         *poutbuf_size= buf_size;
00039 
00040         return 0;
00041     }
00042 
00043     if(avctx->extradata_size != 15 || strcmp(avctx->extradata, "FFCMP3 0.0")){
00044         av_log(avctx, AV_LOG_ERROR, "Extradata invalid %d\n", avctx->extradata_size);
00045         return -1;
00046     }
00047 
00048     header= AV_RB32(avctx->extradata+11) & MP3_MASK;
00049 
00050     lsf     = sample_rate < (24000+32000)/2;
00051     mpeg25  = sample_rate < (12000+16000)/2;
00052     sample_rate_index= (header>>10)&3;
00053     sample_rate= ff_mpa_freq_tab[sample_rate_index] >> (lsf + mpeg25); //in case sample rate is a little off
00054 
00055     for(bitrate_index=2; bitrate_index<30; bitrate_index++){
00056         frame_size = ff_mpa_bitrate_tab[lsf][2][bitrate_index>>1];
00057         frame_size = (frame_size * 144000) / (sample_rate << lsf) + (bitrate_index&1);
00058         if(frame_size == buf_size + 4)
00059             break;
00060         if(frame_size == buf_size + 6)
00061             break;
00062     }
00063     if(bitrate_index == 30){
00064         av_log(avctx, AV_LOG_ERROR, "Could not find bitrate_index.\n");
00065         return -1;
00066     }
00067 
00068     header |= (bitrate_index&1)<<9;
00069     header |= (bitrate_index>>1)<<12;
00070     header |= (frame_size == buf_size + 4)<<16; //FIXME actually set a correct crc instead of 0
00071 
00072     *poutbuf_size= frame_size;
00073     *poutbuf= av_malloc(frame_size + FF_INPUT_BUFFER_PADDING_SIZE);
00074     memcpy(*poutbuf + frame_size - buf_size, buf, buf_size + FF_INPUT_BUFFER_PADDING_SIZE);
00075 
00076     if(avctx->channels==2){
00077         uint8_t *p= *poutbuf + frame_size - buf_size;
00078         if(lsf){
00079             FFSWAP(int, p[1], p[2]);
00080             header |= (p[1] & 0xC0)>>2;
00081             p[1] &= 0x3F;
00082         }else{
00083             header |= p[1] & 0x30;
00084             p[1] &= 0xCF;
00085         }
00086     }
00087 
00088     AV_WB32(*poutbuf, header);
00089 
00090     return 1;
00091 }
00092 
00093 AVBitStreamFilter ff_mp3_header_decompress_bsf={
00094     "mp3decomp",
00095     0,
00096     mp3_header_decompress,
00097 };

Generated on Fri Feb 22 2013 07:24:27 for FFmpeg by  doxygen 1.7.1