Code for converting back and forth between pulse vectors and the correspondig
VQ index.
This commit is contained in:
Timothy B. Terriberry
Jean-Marc Valin
parent
7f4701383b
commit
c4541ae786
4 changed files with 302 additions and 55 deletions
246
libcelt/cwrs.c
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246
libcelt/cwrs.c
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/* (C) 2007 Timothy Terriberry
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*/
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/*
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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- Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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- Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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- Neither the name of the Xiph.org Foundation nor the names of its
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contributors may be used to endorse or promote products derived from
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this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR
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CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/*#include <stdio.h>*/
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#include <stdlib.h>
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#include "cwrs.h"
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/*Returns the numer of ways of choosing _m elements from a set of size _n with
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replacement when a sign bit is needed for each unique element.*/
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#if 0
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static unsigned ncwrs(int _n,int _m){
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static unsigned c[32][32];
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if(_n<0||_m<0)return 0;
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if(!c[_n][_m]){
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if(_m<=0)c[_n][_m]=1;
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else if(_n>0)c[_n][_m]=ncwrs(_n-1,_m)+ncwrs(_n,_m-1)+ncwrs(_n-1,_m-1);
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}
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return c[_n][_m];
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}
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#else
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/*Returns the greatest common divisor of _a and _b.*/
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static unsigned gcd(unsigned _a,unsigned _b){
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unsigned r;
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while(_b){
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r=_a%_b;
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_a=_b;
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_b=r;
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}
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return _a;
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}
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/*Returns _a*b/_d, under the assumption that the result is an integer, avoiding
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overflow.
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It is assumed, but not required, that _b is smaller than _a.*/
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static unsigned umuldiv(unsigned _a,unsigned _b,unsigned _d){
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unsigned d;
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d=gcd(_b,_d);
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return (_a/(_d/d))*(_b/d);
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}
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unsigned ncwrs(int _n,int _m){
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unsigned ret;
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unsigned f;
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unsigned d;
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int i;
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if(_n<0||_m<0)return 0;
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if(_m==0)return 1;
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if(_n==0)return 0;
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ret=0;
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f=_n;
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d=1;
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for(i=1;i<=_m;i++){
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ret+=f*d<<i;
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#if 0
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f=umuldiv(f,_n-i,i+1);
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d=umuldiv(d,_m-i,i);
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#else
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f=(f*(_n-i))/(i+1);
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d=(d*(_m-i))/i;
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#endif
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}
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return ret;
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}
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#endif
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/*Returns the _i'th combination of _m elements chosen from a set of size _n
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with associated sign bits.
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_x: Returns the combination with elements sorted in ascending order.
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_s: Returns the associated sign bits.*/
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void cwrsi(int _n,int _m,unsigned _i,int *_x,int *_s){
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unsigned pn;
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int j;
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int k;
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pn=ncwrs(_n-1,_m);
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for(k=j=0;k<_m;k++){
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unsigned pp;
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unsigned p;
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unsigned t;
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pp=0;
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p=ncwrs(_n-j,_m-k)-pn;
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if(k>0){
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t=p>>1;
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if(t<=_i||_s[k-1])_i+=t;
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}
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pn=ncwrs(_n-j-1,_m-k-1);
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while(p<=_i){
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pp=p;
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j++;
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p+=pn;
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pn=ncwrs(_n-j-1,_m-k-1);
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p+=pn;
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}
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t=p-pp>>1;
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_s[k]=_i-pp>=t;
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_x[k]=j;
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_i-=pp;
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if(_s[k])_i-=t;
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}
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}
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/*Returns the index of the given combination of _m elements chosen from a set
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of size _n with associated sign bits.
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_x: The combination with elements sorted in ascending order.
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_s: The associated sign bits.*/
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unsigned icwrs(int _n,int _m,const int *_x,const int *_s){
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unsigned pn;
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unsigned i;
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int j;
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int k;
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i=0;
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pn=ncwrs(_n-1,_m);
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for(k=j=0;k<_m;k++){
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unsigned pp;
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unsigned p;
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pp=0;
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p=ncwrs(_n-j,_m-k)-pn;
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if(k>0)p>>=1;
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pn=ncwrs(_n-j-1,_m-k-1);
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while(j<_x[k]){
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pp=p;
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j++;
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p+=pn;
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pn=ncwrs(_n-j-1,_m-k-1);
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p+=pn;
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}
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i+=pp;
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if((k==0||_x[k]!=_x[k-1])&&_s[k])i+=p-pp>>1;
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}
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return i;
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}
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/*Converts a combination _x of _m unit pulses with associated sign bits _s into
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a pulse vector _y of length _n.
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_y: Returns the vector of pulses.
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_x: The combination with elements sorted in ascending order.
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_s: The associated sign bits.*/
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void comb2pulse(int _n,int _m,int *_y,const int *_x,const int *_s){
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int j;
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int k;
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int n;
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for(k=j=0;k<_m;k+=n){
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for(n=1;k+n<_m&&_x[k+n]==_x[k];n++);
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while(j<_x[k])_y[j++]=0;
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_y[j++]=_s[k]?-n:n;
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}
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while(j<_n)_y[j++]=0;
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}
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/*Converts a pulse vector vector _y of length _n into a combination of _m unit
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pulses with associated sign bits _s.
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_x: Returns the combination with elements sorted in ascending order.
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_s: Returns the associated sign bits.
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_y: The vector of pulses, whose sum of absolute values must be _m.*/
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void pulse2comb(int _n,int _m,int *_x,int *_s,const int *_y){
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int j;
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int k;
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for(k=j=0;j<_n;j++){
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if(_y[j]){
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int n;
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int s;
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n=abs(_y[j]);
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s=_y[j]<0;
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for(;n-->0;k++){
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_x[k]=j;
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_s[k]=s;
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}
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}
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}
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}
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/*
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#define NMAX (10)
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#define MMAX (9)
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int main(int _argc,char **_argv){
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int n;
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for(n=0;n<=NMAX;n++){
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int m;
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for(m=0;m<=MMAX;m++){
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unsigned nc;
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unsigned i;
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nc=ncwrs(n,m);
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for(i=0;i<nc;i++){
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int x[MMAX];
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int s[MMAX];
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int x2[MMAX];
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int s2[MMAX];
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int y[NMAX];
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int j;
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int k;
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cwrsi(n,m,i,x,s);
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printf("%6u of %u:",i,nc);
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for(k=0;k<m;k++){
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printf(" %c%i",k>0&&x[k]==x[k-1]?' ':s[k]?'-':'+',x[k]);
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}
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printf(" ->");
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if(icwrs(n,m,x,s)!=i){
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fprintf(stderr,"Combination-index mismatch.\n");
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}
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comb2pulse(n,m,y,x,s);
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for(j=0;j<n;j++)printf(" %c%i",y[j]?y[j]<0?'-':'+':' ',abs(y[j]));
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printf("\n");
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pulse2comb(n,m,x2,s2,y);
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for(k=0;k<m;k++)if(x[k]!=x2[k]||s[k]!=s2[k]){
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fprintf(stderr,"Pulse-combination mismatch.\n");
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break;
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}
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}
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printf("\n");
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}
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}
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return 0;
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}
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*/
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