mp4_iquant.c

<VC++视频音频开发>一书的光盘资料。

#include "mp4_vars.h"

#include "mp4_predict.h"
#include "mp4_iquant.h"



#define _iquant_h263(coeff, q_2scale, q_add)	if ((coeff) != 0) {	\
if ((coeff) > 0)	{	\
(coeff) = ((q_2scale) * (coeff)) + (q_add);	}	\
else if ((coeff) < 0)	{	\
(coeff) *= -1;	\
(coeff) = ((q_2scale) * (coeff)) + (q_add);	\
(coeff) *= -1; }	\
}

/**
 *
**/

__inline void iquant (short * psblock, int intraFlag)
{
	int i;
	int q_scale = mp4_state->hdr.quantizer;
	int q_2scale = q_scale << 1;
	int q_add = (q_scale & 1) ? q_scale : (q_scale - 1);

	for (i = intraFlag; i < 64; i++)
	{
		_iquant_h263(psblock[i], q_2scale, q_add);
	}
}


void iquant_typefirst (short * psblock)
{
	int i;
	for (i = 1; i < 64; i++)
	{
		if (psblock[i] != 0) {
			psblock[i] = (psblock[i] * 2 *	mp4_state->hdr.quantizer * 
				mp4_tables->intra_quant_matrix[mp4_tables->zig_zag_scan[i]]) >> 4;
		}
	}
}