huffman.c

ARM MP3解码源代码1.0 有完整的项目文件

/***********************************************
copyright by Haia Tech
www.haia2004.com
************************************************/



/* MPEG Audio Layer-3 decoder             */
/* Bjorn Wesen 1997                       */
/*                                        */
/* Huffman decoder                        */

#include "huffman.h"
#include "common.h"
 
extern	unsigned  int frameNum;

/* lots of tables */

/* code implementing the Huffman decoder for layer-3 */
/* decode the Huffman coded energies of a Granule */

#define BITS_USED ((((datapos - (totpos >> 3)) * 8) % BITSTREAM_BUFSIZE) - \
	dataword_len - (totpos & 7))

static int t_linbits[32] = { 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,2,3,4,6,8,
			     10,13,4,5,6,7,8,9,11,13 };

static unsigned int offset;
static unsigned int  buf_bit_idx=8;
unsigned int buf_byte_idx;

extern unsigned int totpos;
extern unsigned char  buf[BITSTREAM_BUFSIZE];


static unsigned int dataword; 
int dataword_len;
int datapos;
 

extern struct BandIndex sfBandIndex[3];
extern frame_params fr_ps; 

int HuffmanTable_decode(int tbl, 
		    int *x, int *y, int *v, int *w);


void III_hufman_decode(struct Granule *gr,int part2_start,
		       	 int freqline[SBLIMIT][SSLIMIT])
{
    unsigned int reg1, reg2,i; 

	unsigned int part3_length = part2_start + gr->part2_3_length;
	unsigned used;
    int h,*f=&freqline[0][0];

    if(gr->window_switching_flag &&
       gr->block_type == 2)
	{
	
	/* short block regions */
	
	  reg1 = 36;  
	  reg2 = 576;
	
    }
	else
	{
	/* long block regions */

	  reg1 = sfBandIndex[fr_ps.header->sampling_frequency].l[gr->region0_count + 1];
	  reg2 = sfBandIndex[fr_ps.header->sampling_frequency].l[gr->region0_count + gr->region1_count + 2];
    }


    /* fill up dataword, end at a bytealign in the buffer */
    {
	int bitpos = totpos & 7;    //