ratectrl.cpp

H.263的编码程序,加了CPU指令优化,VC版.

#include <stdio.h>
#include "HEnc.h"

int ratectrl(int target_bitrate, int frame_rate, int frame_bits[], int *Quant)
{
	int i,j,k;
	int totalframebits=0;
	int leftbits=0;
	int leftbitsneed=0;
	int differ=0;
	int frame_skip = 0;
	int bpf=target_bitrate/frame_rate;

	if (target_bitrate == 0)
	{
		return 0;
	}

//	printf("\nQI %d\n",*Quant);
//  printf("\nframe_rate,%d\n",frame_rate);	
	for(i=0;i<frame_rate;i++)
	{
		if(frame_bits[i]>0)
			j=i;
	}
//	printf("\nthe last frame_bit:%d\n",j);
	for(k=0;k<=j;k++)
	{
		totalframebits+=frame_bits[k];
	}
//	printf("\ntotalframebits,%d\n",totalframebits);


	leftbits=target_bitrate-totalframebits;//客观上允许这么多比特，是上限
//	printf("\nleftbits:%d\n",leftbits);
	leftbitsneed=target_bitrate*(frame_rate-j-1)/frame_rate;//
//	printf("\nleftbitsneed:%d\n",leftbitsneed);
//	printf("\nbpf:%d\n",target_bitrate/frame_rate);	
	differ=leftbitsneed-leftbits;
//	printf("\ndiffer:%d\n",differ);
	if(differ<=0)
	{
		(*Quant)--;
	}
	else if(differ<=bpf)
	{
		(*Quant)++;
	}
	else
	{
		(*Quant)++;
		frame_skip=differ/bpf;
	}

	*Quant = mmin(28,mmax(4, *Quant));
	
	return frame_skip;

}