/**************************************************************************************
* Function: DCT4
*
* Description: type-IV DCT
*
* Inputs: table index (for transform size)
* buffer of nmdct samples
* number of guard bits in the input buffer
*
* Outputs: processed samples in same buffer
*
* Return: none
*
* Notes: operates in-place
* if number of guard bits in input is < GBITS_IN_DCT4, the input is
* scaled (>>) before the DCT4 and rescaled (<<, with clipping) after
* the DCT4 (rare)
* the output has FBITS_LOST_DCT4 fewer fraction bits than the input
* the output will always have at least 1 guard bit (GBITS_IN_DCT4 >= 4)
* int bits gained per stage (PreMul + FFT + PostMul)
* short blocks = (-5 + 4 + 2) = 1 total
* long blocks = (-8 + 7 + 2) = 1 total
**************************************************************************************/
void DCT4(int tabidx, int *coef, int gb)
{
int es;
/* fast in-place DCT-IV - adds guard bits if necessary */
if (gb < GBITS_IN_DCT4) {
es = GBITS_IN_DCT4 - gb;
PreMultiplyRescale(tabidx, coef, es);
R4FFT(tabidx, coef);
PostMultiplyRescale(tabidx, coef, es);
} else {
PreMultiply(tabidx, coef);
R4FFT(tabidx, coef);
PostMultiply(tabidx, coef);
}
}
/**************************************************************************************
* Function: IMLTNoWindow
*
* Description: inverse MLT without window or overlap-add
*
* Inputs: table index (for transform size)
* buffer of nmlt samples
* number of guard bits in the input buffer
*
* Outputs: processed samples in same buffer
*
* Return: none
*
* Notes: operates in-place, and generates nmlt output samples from nmlt input
* samples (doesn't do synthesis window which expands to 2*nmlt samples)
* if number of guard bits in input is < GBITS_IN_IMLT, the input is
* scaled (>>) before the IMLT and rescaled (<<, with clipping) after
* the IMLT (rare)
* the output has FBITS_LOST_IMLT fewer fraction bits than the input
* the output will always have at least 1 guard bit
**************************************************************************************/
void IMLTNoWindow(int tabidx, int *mlt, int gb)
{
int es;
/* fast in-place DCT-IV - adds guard bits if necessary */
if (gb < GBITS_IN_IMLT) {
es = GBITS_IN_IMLT - gb;
PreMultiplyRescale(tabidx, mlt, es);
R4FFT(tabidx, mlt);
PostMultiplyRescale(tabidx, mlt, es);
} else {
PreMultiply(tabidx, mlt);
R4FFT(tabidx, mlt);
PostMultiply(tabidx, mlt);
}
return;
}