gistfile1.c

void playWav(char* filename, float samplerate)
{
    int fp= STDIN_FILENO;
    if(filename[0]!='-') fp = open(filename, 'r');
    //int sz = lseek(fp, 0L, SEEK_END);
    //lseek(fp, 0L, SEEK_SET);
    //short* data = (short*)malloc(sz);
    //read(fp, data, sz);
    
    int bufPtr=0;
    float datanew, dataold = 0;
    short data;
    
    for (int i=0; i<22; i++)
       read(fp, &data, 2);  // read past header
    
    while (read(fp, &data, 2)) {
        float fmconstant = samplerate * 50.0e-6;  // for pre-emphisis filter.  50us time constant
        int clocksPerSample = 22500.0/samplerate*1400.0;  // for timing
        
        datanew = (float)(data)/32767;
        
        float sample = datanew + (dataold-datanew) / (1-fmconstant);  // fir of 1 + s tau
        sample = datanew;
        float dval = sample*2;  // actual transmitted sample.  15 is bandwidth (about 75 kHz)
        
        int intval = (int)(round(dval));  // integer component
        float frac = (dval - (float)intval)/2 + 0.5;
        unsigned int fracval = frac*clocksPerSample;
//        if (intval < 3) printf("%d %d\n",intval, fracval); 
        bufPtr++;
        while( ACCESS(DMABASE + 0x04 /* CurBlock*/) ==  (int)(instrs[bufPtr].p)) usleep(1000);
        ((struct CB*)(instrs[bufPtr].v))->SOURCE_AD = (int)constPage.p + 2048 + intval*4 - 4 ;
        
        bufPtr++;
        while( ACCESS(DMABASE + 0x04 /* CurBlock*/) ==  (int)(instrs[bufPtr].p)) usleep(1000);
        ((struct CB*)(instrs[bufPtr].v))->TXFR_LEN = clocksPerSample-fracval;
        
        bufPtr++;
        while( ACCESS(DMABASE + 0x04 /* CurBlock*/) ==  (int)(instrs[bufPtr].p)) usleep(1000);
        ((struct CB*)(instrs[bufPtr].v))->SOURCE_AD = (int)constPage.p + 2048 + intval*4+4;
        
        bufPtr=(bufPtr+1) % (1024);
        while( ACCESS(DMABASE + 0x04 /* CurBlock*/) ==  (int)(instrs[bufPtr].p)) usleep(1000);
        ((struct CB*)(instrs[bufPtr].v))->TXFR_LEN = fracval;
        
        dataold = datanew;
    }
    close(fp);
}