mirror of https://github.com/mpv-player/mpv
123 lines
3.7 KiB
C
123 lines
3.7 KiB
C
/*
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* This file is part of MPlayer.
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*
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* MPlayer is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* MPlayer is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with MPlayer; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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#include <stdio.h>
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#include <stdint.h>
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#include "config.h"
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#include "mp3_hdr.h"
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#include "mp_msg.h"
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//----------------------- mp3 audio frame header parser -----------------------
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static const uint16_t tabsel_123[2][3][16] = {
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{ {0,32,64,96,128,160,192,224,256,288,320,352,384,416,448,0},
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{0,32,48,56, 64, 80, 96,112,128,160,192,224,256,320,384,0},
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{0,32,40,48, 56, 64, 80, 96,112,128,160,192,224,256,320,0} },
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{ {0,32,48,56,64,80,96,112,128,144,160,176,192,224,256,0},
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{0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,0},
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{0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,0} }
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};
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static const int freqs[9] = { 44100, 48000, 32000, // MPEG 1.0
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22050, 24000, 16000, // MPEG 2.0
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11025, 12000, 8000}; // MPEG 2.5
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/*
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* return frame size or -1 (bad frame)
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*/
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int mp_get_mp3_header(unsigned char* hbuf,int* chans, int* srate, int* spf, int* mpa_layer, int* br){
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int stereo,lsf,framesize,padding,bitrate_index,sampling_frequency, divisor;
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int bitrate;
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int layer;
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static const int mult[3] = { 12000, 144000, 144000 };
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uint32_t newhead =
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hbuf[0] << 24 |
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hbuf[1] << 16 |
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hbuf[2] << 8 |
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hbuf[3];
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// head_check:
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if( (newhead & 0xffe00000) != 0xffe00000 ){
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mp_msg(MSGT_DEMUXER,MSGL_DBG2,"head_check failed\n");
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return -1;
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}
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layer = 4-((newhead>>17)&3);
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if(layer==4){
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mp_msg(MSGT_DEMUXER,MSGL_DBG2,"not layer-1/2/3\n");
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return -1;
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}
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sampling_frequency = (newhead>>10)&0x3; // valid: 0..2
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if(sampling_frequency==3){
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mp_msg(MSGT_DEMUXER,MSGL_DBG2,"invalid sampling_frequency\n");
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return -1;
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}
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if( newhead & (1<<20) ) {
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// MPEG 1.0 (lsf==0) or MPEG 2.0 (lsf==1)
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lsf = !(newhead & (1<<19));
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sampling_frequency += lsf*3;
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} else {
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// MPEG 2.5
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lsf = 1;
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sampling_frequency += 6;
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}
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bitrate_index = (newhead>>12)&0xf; // valid: 1..14
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padding = (newhead>>9)&0x1;
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stereo = ( ((newhead>>6)&0x3) == 3) ? 1 : 2;
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bitrate = tabsel_123[lsf][layer-1][bitrate_index];
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framesize = bitrate * mult[layer-1];
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mp_msg(MSGT_DEMUXER,MSGL_DBG2,"FRAMESIZE: %d, layer: %d, bitrate: %d, mult: %d\n",
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framesize, layer, tabsel_123[lsf][layer-1][bitrate_index], mult[layer-1]);
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if(!framesize){
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mp_msg(MSGT_DEMUXER,MSGL_DBG2,"invalid framesize/bitrate_index\n");
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return -1;
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}
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divisor = layer == 3 ? (freqs[sampling_frequency] << lsf) : freqs[sampling_frequency];
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framesize /= divisor;
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framesize += padding;
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if(layer==1)
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framesize *= 4;
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if(srate)
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*srate = freqs[sampling_frequency];
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if(spf) {
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if(layer == 1)
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*spf = 384;
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else if(layer == 2)
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*spf = 1152;
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else if(sampling_frequency > 2) // not 1.0
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*spf = 576;
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else
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*spf = 1152;
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}
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if(mpa_layer) *mpa_layer = layer;
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if(chans) *chans = stereo;
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if(br) *br = bitrate;
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return framesize;
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}
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