kolibrios-gitea/programs/media/ac97snd/trunk/mpg/common.c

#include <stdlib.h>
#include "mpg123.h"

int tabsel_123[2][3][16] = {
   { {0,32,64,96,128,160,192,224,256,288,320,352,384,416,448,},
     {0,32,48,56, 64, 80, 96,112,128,160,192,224,256,320,384,},
     {0,32,40,48, 56, 64, 80, 96,112,128,160,192,224,256,320,} },

   { {0,32,48,56,64,80,96,112,128,144,160,176,192,224,256,},
     {0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,},
     {0,8,16,24,32,40,48,56,64,80,96,112,128,144,160,} }
};

long freqs[9] = { 44100, 48000, 32000,
                  22050, 24000, 16000 ,
                  11025 , 12000 , 8000 };

#define HDRCMPMASK 0xfffffd00

struct bitstream_info bsi;

int ssize;
 
unsigned long read_header(BYTE *mpeg)
{ 	unsigned long hdr;
    
	  hdr = *mpeg++;
	  hdr <<= 8;
	  hdr |= *mpeg++;
	  hdr <<= 8;
	  hdr |= *mpeg++;
	  hdr <<= 8;
	  hdr |= *mpeg++;
	  return hdr; 
};

int head_check(unsigned long head)
{
    if( (head & 0xffe00000) != 0xffe00000)
	return FALSE;
    if(!((head>>17)&3))
	return FALSE;
    if( ((head>>12)&0xf) == 0xf)
	return FALSE;
    if( ((head>>10)&0x3) == 0x3 )
	return FALSE;
    return TRUE;
}

int decode_header(struct frame *fr,unsigned long newhead)
{
    if( newhead & (1<<20) ) {
      fr->lsf = (newhead & (1<<19)) ? 0x0 : 0x1;
      fr->mpeg25 = 0;
    }
    else {
      fr->lsf = 1;
      fr->mpeg25 = 1;
    }
    
    fr->lay = 4-((newhead>>17)&3);
    if( ((newhead>>10)&0x3) == 0x3) {
      fprintf(stderr,"Stream error, reserved sampling rate\n");
      return 0;
    }
    if(fr->mpeg25) {
      fr->sampling_frequency = 6 + ((newhead>>10)&0x3);
    }
    else
      fr->sampling_frequency = ((newhead>>10)&0x3) + (fr->lsf*3);
    fr->error_protection = ((newhead>>16)&0x1)^0x1;

    if(fr->mpeg25) /* allow Bitrate change for 2.5 ... */
      fr->bitrate_index = ((newhead>>12)&0xf);

    fr->bitrate_index = ((newhead>>12)&0xf);
    fr->padding   = ((newhead>>9)&0x1);
    fr->extension = ((newhead>>8)&0x1);
    fr->mode      = ((newhead>>6)&0x3);
    fr->mode_ext  = ((newhead>>4)&0x3);
    fr->copyright = ((newhead>>3)&0x1);
    fr->original  = ((newhead>>2)&0x1);
    fr->emphasis  = newhead & 0x3;

    fr->stereo    = (fr->mode == MPG_MD_MONO) ? 1 : 2;

    if(!fr->bitrate_index)
    {
      fprintf(stderr, "Stream error, free format bitrate index not supported\n");
      return 0;
    }

    switch(fr->lay)
    {
      case 1:
        fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ? 
                         (fr->mode_ext<<2)+4 : 32;
        fr->framesize  = (long) tabsel_123[fr->lsf][0][fr->bitrate_index] * 12000;
        fr->framesize /= freqs[fr->sampling_frequency];
        fr->framesize  = ((fr->framesize+fr->padding)<<2)-4;
        break;
      case 2:
        fr->jsbound = (fr->mode == MPG_MD_JOINT_STEREO) ?
                         (fr->mode_ext<<2)+4 : fr->II_sblimit;
        fr->framesize = (long) tabsel_123[fr->lsf][1][fr->bitrate_index] * 144000;
        fr->framesize /= freqs[fr->sampling_frequency];
        fr->framesize += fr->padding - 4;
        break;

      case 3:
        fr->do_layer = do_layer3;
        if(fr->lsf)
          ssize = (fr->stereo == 1) ? 9 : 17;
        else
          ssize = (fr->stereo == 1) ? 17 : 32;

        if(fr->error_protection)
          ssize += 2;
          fr->framesize  = (long) tabsel_123[fr->lsf][2][fr->bitrate_index] * 144000;
          fr->framesize /= freqs[fr->sampling_frequency]<<(fr->lsf);
          fr->framesize = fr->framesize + fr->padding - 4;
        break; 
      default:
        return (0);
    }
    return 1;
}

//void set_pointer(long backstep)
//{
//  bsi.wordpointer = bsbuf + ssize - backstep;
//  if (backstep)
//    memcpy(bsi.wordpointer,bsbufold+fsizeold-backstep,backstep);
//  bsi.bitindex = 0; 
//}