mirror of https://github.com/mpv-player/mpv
92 lines
2.4 KiB
C
92 lines
2.4 KiB
C
#include <stdio.h>
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#include "config.h"
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//----------------------- mp3 audio frame header parser -----------------------
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static int tabsel_123[2][3][16] = {
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{ {0,32,64,96,128,160,192,224,256,288,320,352,384,416,448,},
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{0,32,48,56, 64, 80, 96,112,128,160,192,224,256,320,384,},
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{0,32,40,48, 56, 64, 80, 96,112,128,160,192,224,256,320,} },
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{ {0,32,48,56,64,80,96,112,128,144,160,176,192,224,256,},
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{0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,},
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{0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,} }
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};
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static long freqs[9] = { 44100, 48000, 32000, 22050, 24000, 16000 , 11025 , 12000 , 8000 };
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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_decode_mp3_header(unsigned char* hbuf){
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int stereo,ssize,crc,lsf,mpeg25,framesize,padding,bitrate_index,sampling_frequency;
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unsigned long 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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// printf("head=0x%08X\n",newhead);
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#if 1
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// head_check:
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if( (newhead & 0xffe00000) != 0xffe00000 ||
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(newhead & 0x0000fc00) == 0x0000fc00){
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printf("head_check failed\n");
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return -1;
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}
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#endif
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if((4-((newhead>>17)&3))!=3){ printf("not layer-3\n"); return -1;}
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if( newhead & ((long)1<<20) ) {
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lsf = (newhead & ((long)1<<19)) ? 0x0 : 0x1;
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mpeg25 = 0;
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} else {
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lsf = 1;
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mpeg25 = 1;
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}
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if(mpeg25)
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sampling_frequency = 6 + ((newhead>>10)&0x3);
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else
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sampling_frequency = ((newhead>>10)&0x3) + (lsf*3);
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if(sampling_frequency>8){
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printf("invalid sampling_frequency\n");
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return -1; // valid: 0..8
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}
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crc = ((newhead>>16)&0x1)^0x1;
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bitrate_index = ((newhead>>12)&0xf);
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padding = ((newhead>>9)&0x1);
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// fr->extension = ((newhead>>8)&0x1);
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// fr->mode = ((newhead>>6)&0x3);
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// fr->mode_ext = ((newhead>>4)&0x3);
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// fr->copyright = ((newhead>>3)&0x1);
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// fr->original = ((newhead>>2)&0x1);
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// fr->emphasis = newhead & 0x3;
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stereo = ( (((newhead>>6)&0x3)) == 3) ? 1 : 2;
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if(!bitrate_index){
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fprintf(stderr,"Free format not supported.\n");
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return -1;
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}
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if(lsf)
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ssize = (stereo == 1) ? 9 : 17;
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else
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ssize = (stereo == 1) ? 17 : 32;
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if(crc) ssize += 2;
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framesize = (long) tabsel_123[lsf][2][bitrate_index] * 144000;
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framesize /= freqs[sampling_frequency]<<lsf;
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framesize += padding;
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// if(framesize<=0 || framesize>MAXFRAMESIZE) return FALSE;
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return framesize;
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}
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