layer2.c

由bmp生成mpeg2 的I_frame 数据

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	}
};

int decode_layer2(LAYER2_HEADER *head, unsigned char *buffer, LAYER2_WORK *work, short *pcm)
{
	if(head->channel == 2){
		return decode_layer2_stereo(head, buffer, work, pcm);
	}else{
		return decode_layer2_monaural(head, buffer, work, pcm);
	}
}
	
static int decode_layer2_stereo(LAYER2_HEADER *head, unsigned char *buffer, LAYER2_WORK *work, short *pcm)
{
	int i,k,n,m;
	int step;
	int bits;
	int o1,o2;
	
	unsigned int code;
	
	int sb,ch,gr;

	int allocation[32][2];
	int scfsi[32][2];
	int scalefactor[32][2][3];
	double sample[12][3][32][2];

	double U[1024];
	double W[1024];

	double s[2];
	int ss[2];
	
	MEMORY_STREAM ms;

	const int *table_b2_nbal;
	const int **table_b2;

	ms_set_buffer(&ms, buffer, head->framesize);

	if(head->has_crc){
		ms_get_bits(&ms, 16);
	}

	if(head->sblimit > 20){
		table_b2_nbal = table_b2ab_nbal;
		table_b2 = table_b2ab;
	}else{
		table_b2_nbal = table_b2cd_nbal;
		table_b2 = table_b2cd;
	}

	/* read allocation */
	for(sb=0;sb<head->bound;sb++){
		for(ch=0;ch<2;ch++){
			n = ms_get_bits(&ms, table_b2_nbal[sb]);
			allocation[sb][ch] = table_b2[sb][n];
		}
	}

	for(sb=head->bound;sb<head->sblimit;sb++){
		n =