sac_e.c

文件内包含H.263视频编码算法和解码算法2个文件

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

#define   q1_e    16384
#define   q2_e    32768
#define   q3_e    49152
#define   top_e   65535

static long   low_e=0, high_e=top_e, opposite_bits_e=0, length_e=0, zerorun_e=0;


int AR_Encode(int index, int cumul_freq[ ])
{
	int bitcount=0;
	
	if (index<0) 
		return -1; /* Escape Code */
	
	length_e = high_e - low_e + 1;
	high_e = low_e - 1 + (length_e * cumul_freq[index]) / cumul_freq[0];
	low_e += (length_e * cumul_freq[index+1]) / cumul_freq[0];
	
	for ( ; ; ) {
		if (high_e < q2_e) {
			bitcount+=bit_opp_bits(0);
		}
		else if (low_e >= q2_e) {
			bitcount+=bit_opp_bits(1);	
			low_e -= q2_e; 
			high_e -= q2_e;
		}
		else if (low_e >= q1_e && high_e < q3_e) {
			opposite_bits_e += 1; 
			low_e -= q1_e; 
			high_e -= q1_e;
		}
		else break;
		
		low_e *= 2; 
		high_e = 2*high_e+1;
	}
	return bitcount;
}

int bit_opp_bits(int bit) /* Output a bit and the following opposite bits */              
{                                   
	int bitcount=0;
	
	bitcount = bit_in_psc_layer(bit);
	
	while(opposite_bits_e > 0){
		bitcount += bit_in_psc_layer(!bit);
		opposite_bits_e--;
	}
	return bitcount;
}


int encoder_flush()
{
	int bitcount = 0;
	
	if (trace)
		fprintf(tf, "encoder_flush:\n");
	
	opposite_bits_e++;
	if (low_e < q1_e) {
		bitcount+=bit_opp_bits(0);
	}
	else {
		bitcount+=bit_opp_bits(1);
	}
	low_e = 0; 
	high_e = top_e;
	
	zerorun_e=0;
	
	return bitcount;
}


int bit_in_psc_layer(int bit)
{
	void putbits (int, int);
	int bitcount = 0;
	
	if (zerorun_e > 13) {
		if (trace)
			fprintf(tf, "PSC emulation ... Bit stuffed.\n");
		putbits (1, 1);
		bitcount++;
		zerorun_e = 0;
	}
	
	putbits (1, bit);
	bitcount++;
	
	if (bit)
		zerorun_e = 0;
	else
		zerorun_e++;
	
	return bitcount;
}


int indexfn(int value, int table[], int max)
{
	int n=0;
	
	while(1) {
		if (table[n++]==value) return n-1;
		if (n>max) return -1;
	}
	
}