#pragma CODE_SECTION(iirDirectform1StereoProcess, ".criticalSectionInternal")
void iirDirectform1StereoProcess(float *restrict in, float *restrict out, float (*x)[6], float (*y)[6], iirdirectform1 *filt, int len, int numFilters, Bool on)
{
    float *signalInL, *signalOutL, *signalInR, *signalOutR;
    int i, j;
    iirdirectform1 *restrict filt1 = filt;
    signalInL = in;
    signalOutL = out;
    signalInR = in + len;
    signalOutR = out + len;
    // bypass filter
    if (on == FALSE)
    {
        for (j=0; j<len; j++)
        {
            *signalOutL++ = *signalInL++;
            *signalOutR++ = *signalInR++;
        }
    }
    else
    {
#pragma MUST_ITERATE(1, , )
        for (j=0; j<len; j++)
        {
            x[0][0] = *signalInL++;
            x[0][3] = *signalInR++;
#pragma MUST_ITERATE(1, , )
            for (i=0; i<numFilters; i++)
            {
                y[i][0] = filt1[i].b0 * x[i][0] + filt1[i].b1 * x[i][1] + filt1[i].b2 * x[i][2] - filt1[i].a1 * y[i][1] - filt1[i].a2 * y[i][2];
                y[i][2] = y[i][1];
                y[i][1] = y[i][0];
                x[i][2] = x[i][1];
                x[i][1] = x[i][0];

                y[i][3] = filt1[i].b0 * x[i][3] + filt1[i].b1 * x[i][4] + filt1[i].b2 * x[i][5] - filt1[i].a1 * y[i][4] - filt1[i].a2 * y[i][5];
                y[i][5] = y[i][4];
                y[i][4] = y[i][3];
                x[i][5] = x[i][4];
                x[i][4] = x[i][3];

                x[i+1][0] = y[i][0];
                x[i+1][3] = y[i][3];
            }
            *signalOutL++ = y[numFilters-1][0];
            *signalOutR++ = y[numFilters-1][3];
        }
    }

}