huffman.c

《Visual C++小波变换技术与工程实践》作者：靳济芳。书上的代码。第3章：语音的去噪处理

/*
 * FAAC - Freeware Advanced Audio Coder
 * Copyright (C) 2001 Menno Bakker
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.

 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * $Id: huffman.c,v 1.5 2001/06/04 23:02:24 wmay Exp $
 */

#include <math.h>
#include <stdlib.h>

#include "huffman.h"
#include "coder.h"
#include "bitstream.h"
#include "util.h"

#include "hufftab.h"

void HuffmanInit(CoderInfo *coderInfo, unsigned int numChannels)
{
	unsigned int channel;

	for (channel = 0; channel < numChannels; channel++) {
		coderInfo[channel].data = (int*)AllocMemory(5*FRAME_LEN*sizeof(int));
		coderInfo[channel].len = (int*)AllocMemory(5*FRAME_LEN*sizeof(int));
	}
}

void HuffmanEnd(CoderInfo *coderInfo, unsigned int numChannels)
{
	unsigned int channel;

	for (channel = 0; channel < numChannels; channel++) {
		if (coderInfo[channel].data) FreeMemory(coderInfo[channel].data);
		if (coderInfo[channel].len) FreeMemory(coderInfo[channel].len);
	}
}

int BitSearch(CoderInfo *coderInfo,
			  int *quant)  /* Quantized spectral values */
  /*
  This function inputs a vector of quantized spectral data, quant[][], and returns a vector,
  'book_vector[]' that describes how to group together the scalefactor bands into a smaller
  number of sections.  There are MAX_SCFAC_BANDS elements in book_vector (equal to 49 in the
  case of long blocks and 112 for short blocks), and each element has a huffman codebook 
  number assigned to it.

  For a quick and simple algorithm, this function performs a binary
  search across the sfb's (scale factor bands).  On the first approach, it calculates the 
  needed amount of bits if every sfb were its own section and transmitted its own huffman 
  codebook value side information (equal to 9 bits for a long block, 7 for a short).  The 
  next iteration combines adjacent sfb's, and calculates the bit rate for length two sfb 
  sections.  If any wider two-sfb section requires fewer bits than the sum of the two 
  single-sfb sections (below it in the binary tree), then the wider section will be chosen.
  This process occurs until the sections are split into three uniform parts, each with an
  equal amount of sfb's contained.  

  The binary tree is stored as a two-dimensional array.  Since this tree is not full, (there
  are only 49 nodes, not 2^6 = 64), the numbering is a little complicated.  If the tree were
  full, the top node would be 1.  It's children would be 2 and 3.  But, since this tree
  is not full, the top row of three nodes are numbered {4,5,6}.  The row below it is
  {8,9,10,11,12,13}, and so on.  

  The binary tree is called bit_stats[112][3].  There are 112 total nodes (some are not
  used since it's not full).  bit_stats[x][0] holds the bit totals needed for the sfb sectioning
  strategy represented by the node x in the tree.  bit_stats[x][1] holds the optimal huffman
  codebook table that minimizes the bit rate, given the sectioning boundaries dictated by node x.
*/

{
	int i,j,k,n;
	int hop;
	int min_book_choice[112][3];
	int bit_stats[240][3];
	int total_bit_count;
	int levels;
	double fraction;

	/* Set local pointer to coderInfo book_vector */
	int* book_vector = coderInfo -> book_vector;

	levels = (int) ((log((double)coderInfo->nr_of_sfb)/log((double)2.0))+1);
	fraction = (pow(2,levels)+coderInfo->nr_of_sfb)/(double)(pow(2,levels));

/* #define SLOW */

#ifdef SLOW
	for(i = 0; i < 5; i++) {
#else
		i = 0;
#endif
		hop = 1 << i;

		NoiselessBitCount(coderInfo, quant, hop, min_book_choice);

		/* load up the (not-full) binary search tree with the min_book_choice values */
		k=0;
		total_bit_count = 0;

		for (j=(int)(pow(2,levels-i)); j<(int)(fraction*pow(2,levels-i)); j++)
		{
			bit_stats[j][0] = min_book_choice[k][0]; /* the minimum bit cost for this section */
			bit_stats[j][1] = min_book_choice[k][1]; /* used with this huffman book number */

			if (i>0){  /* not on the lowest level, grouping more than one signle scalefactor band per section*/
				if  (bit_stats[j][0] < bit_stats[2*j][0] + bit_stats[2*j+1][0]){

					/* it is cheaper to combine surrounding sfb secionts into one larger huffman book section */
					for(n=k;n<k+hop;n++) { /* write the optimal huffman book value for the new larger section */
						if ( (book_vector[n]!=INTENSITY_HCB)&&(book_vector[n]!=INTENSITY_HCB2) ) { /* Don't merge with IS bands */
							book_vector[n] = bit_stats[j][1];
						}
					}
				} else {  /* it was cheaper to transmit the smaller huffman table sections */
					bit_stats[j][0] = bit_stats[2*j][0] + bit_stats[2*j+1][0];
				}
			} else {  /* during the first stage of the iteration, all sfb's are individual sections */
				if ( (book_vector[k]!=INTENSITY_HCB)&&(book_vector[k]!=INTENSITY_HCB2) ) {
					book_vector[k] = bit_stats[j][1];  /* initially, set all sfb's to their own optimal section table values */
				}
			}
			total_bit_count = total_bit_count +  bit_stats[j][0];
			k=k+hop;
		}
#ifdef SLOW
	}
#endif
	/*   book_vector[k] = book_vector[k-1]; */
	return(total_bit_count);
}


int NoiselessBitCount(CoderInfo *coderInfo,
					  int *quant,
					  int hop,
					  int min_book_choice[112][3])
{
  int i,j,k;

  /*
     This function inputs:
     - the quantized spectral data, 'quant[]';
     - all of the huffman codebooks, 'huff[][]';
     - the size of the sections, in scalefactor bands (SFB's), 'hop';
     - an empty matrix, min_book_choice[][] passed to it;

     This function outputs:
     - the matrix, min_book_choice.  It is a two dimensional matrix, with its
     rows corresponding to spectral sections.  The 0th column corresponds to
     the bits needed to code a section with 'hop' scalefactors bands wide, all using
     the same huffman codebook.  The 1st column contains the huffman codebook number
     that allows the minimum number of bits to be used.

     Other notes:
     - Initally, the dynamic range is calculated for each spectral section.  The section
     can only be entropy coded with books that have an equal or greater dynamic range
     than the section's spectral data.  The exception to this is for the 11th ESC codebook.
     If the dynamic range is larger than 16, then an escape code is appended after the
     table 11 codeword which encodes the larger value explicity in a pseudo-non-uniform
     quantization method.

     */

	int max_sb_coeff;
	int book_choice[12][2];
	int total_bits_cost = 0;
	int offset, length, end;
	int q;

	/* set local pointer to sfb_offset */
	int *sfb_offset = coderInfo->sfb_offset;
	int nr_of_sfb = coderInfo->nr_of_sfb;

	/* each section is 'hop' scalefactor bands wide */
	for (i=0; i < nr_of_sfb; i=i+hop){ 
		if ((i+hop) > nr_of_sfb)
			q = nr_of_sfb;
		else
			q = i+hop;

		{
			
			/* find the maximum absolute value in the current spectral section, to see what tables are available to use */
			max_sb_coeff = 0;
			for (j=sfb_offset[i]; j<sfb_offset[q]; j++){  /* snl */
				if (ABS(quant[j]) > max_sb_coeff)
					max_sb_coeff = ABS(quant[j]);
			}

			j = 0;
			offset = sfb_offset[i];
			if ((i+hop) > nr_of_sfb){
				end = sfb_offset[nr_of_sfb];
			} else
				end = sfb_offset[q];
			length = end - offset;

			/* all spectral coefficients in this section are zero */
			if (max_sb_coeff == 0) { 
				book_choice[j][0] = CalcBits(coderInfo,0,quant,offset,length);
				book_choice[j++][1] = 0;

			}
			else {  /* if the section does have non-zero coefficients */
				if(max_sb_coeff < 2){
					book_choice[j][0] = CalcBits(coderInfo,1,quant,offset,length);
					book_choice[j++][1] = 1;
					book_choice[j][0] = CalcBits(coderInfo,2,quant,offset,length);
					book_choice[j++][1] = 2;
					book_choice[j][0] = CalcBits(coderInfo,3,quant,offset,length);
					book_choice[j++][1] = 3;
				}
				else if (max_sb_coeff < 3){
					book_choice[j][0] = CalcBits(coderInfo,3,quant,offset,length);
					book_choice[j++][1] = 3;
					book_choice[j][0] = CalcBits(coderInfo,4,quant,offset,length);
					book_choice[j++][1] = 4;
					book_choice[j][0] = CalcBits(coderInfo,5,quant,offset,length);
					book_choice[j++][1] = 5;
				}
				else if (max_sb_coeff < 5){
					book_choice[j][0] = CalcBits(coderInfo,5,quant,offset,length);
					book_choice[j++][1] = 5;
					book_choice[j][0] = CalcBits(coderInfo,6,quant,offset,length);
					book_choice[j++][1] = 6;
					book_choice[j][0] = CalcBits(coderInfo,7,quant,offset,length);
					book_choice[j++][1] = 7;
				}
				else if (max_sb_coeff < 8){
					book_choice[j][0] = CalcBits(coderInfo,7,quant,offset,length);
					book_choice[j++][1] = 7;
					book_choice[j][0] = CalcBits(coderInfo,8,quant,offset,length);
					book_choice[j++][1] = 8;
					book_choice[j][0] = CalcBits(coderInfo,9,quant,offset,length);
					book_choice[j++][1] = 9;
				}
				else if (max_sb_coeff < 13){
					book_choice[j][0] = CalcBits(coderInfo,9,quant,offset,length);
					book_choice[j++][1] = 9;
					book_choice[j][0] = CalcBits(coderInfo,10,quant,offset,length);
					book_choice[j++][1] = 10;
				}
				/* (max_sb_coeff >= 13), choose table 11 */
				else {
					book_choice[j][0] = CalcBits(coderInfo,11,quant,offset,length);
					book_choice[j++][1] = 11;
				}
			}

			/* find the minimum bit cost and table number for huffman coding this scalefactor section */
			min_book_choice[i][0] = 100000;

			for(k=0;k<j;k++){
				if (book_choice[k][0] < min_book_choice[i][0]){
					min_book_choice[i][1] = book_choice[k][1];
					min_book_choice[i][0] = book_choice[k][0];
				}
			}
			total_bits_cost += min_book_choice[i][0];
		}
	}
	return(total_bits_cost);
}



static int CalculateEscSequence(int input, int *len_esc_sequence)
/* 
   This function takes an element that is larger than 16 and generates the base10 value of the
   equivalent escape sequence.  It returns the escape sequence in the variable, 'output'.  It
   also passed the length of the escape sequence through the parameter, 'len_esc_sequence'.
*/

{
	float x,y;
	int output;
	int N;

	N = -1;
	y = (float)ABS(input);
	x = y / 16;

	while (x >= 1) {
		N++;
		x = x/2;
	}

	*len_esc_sequence = 2*N + 5;  /* the length of the escape sequence in bits */

	output = (int)((pow(2,N) - 1)*pow(2,N+5) + y - pow(2,N+4));
	return(output);
}

int OutputBits(CoderInfo *coderInfo,
			   int book,
			   int *quant,
			   int offset,
			   int length)
{
  /*