sharedbook.c

fix point版本的Ogg Vorbis decoder

/********************************************************************
 *                                                                  *
 * THIS FILE IS PART OF THE OggVorbis SOFTWARE CODEC SOURCE CODE.   *
 * USE, DISTRIBUTION AND REPRODUCTION OF THIS LIBRARY SOURCE IS     *
 * GOVERNED BY A BSD-STYLE SOURCE LICENSE INCLUDED WITH THIS SOURCE *
 * IN 'COPYING'. PLEASE READ THESE TERMS BEFORE DISTRIBUTING.       *
 *                                                                  *
 * THE OggVorbis SOURCE CODE IS (C) COPYRIGHT 1994-2002             *
 * by the XIPHOPHORUS Company http://www.xiph.org/                  *
 *                                                                  *
 ********************************************************************

 function: basic shared codebook operations
 last mod: $Id: sharedbook.c,v 1.27 2002/01/22 08:06:07 xiphmont Exp $

 ********************************************************************/

#include <stdlib.h>
#include <math.h>
#include <string.h>
#include "ogg.h"
#include "os.h"
#include "misc.h"
#include "vorbis_codec.h"
#include "codebook.h"
#include "scales.h"

/**** pack/unpack helpers ******************************************/
int _ilog(unsigned int v){
  int ret=0;
  while(v){
    ret++;
    v>>=1;
  }
  return(ret);
}

/* 32 bit float (not IEEE; nonnormalized mantissa +
   biased exponent) : neeeeeee eeemmmmm mmmmmmmm mmmmmmmm 
   Why not IEEE?  It's just not that important here. */

#define VQ_FEXP 10
#define VQ_FMAN 21
#define VQ_FEXP_BIAS 768 /* bias toward values smaller than 1. */

float _float32_unpack(long val){
  double mant=val&0x1fffff;
  int    sign=val&0x80000000;
  long   exp =(val&0x7fe00000L)>>VQ_FMAN;
  if(sign)mant= -mant;
  return(ldexp(mant,exp-(VQ_FMAN-1)-VQ_FEXP_BIAS));
}

/* given a list of word lengths, generate a list of codewords.  Works
   for length ordered or unordered, always assigns the lowest valued
   codewords first.  Extended to handle unused entries (length 0) */
ogg_uint32_t *_make_words(long *l,long n,long sparsecount){
  long i,j,count=0;
  ogg_uint32_t marker[33];
  ogg_uint32_t *r=_ogg_malloc((sparsecount?sparsecount:n)*sizeof(*r));
  memset(marker,0,sizeof(marker));

  for(i=0;i<n;i++){
    long length=l[i];
    if(length>0){
      ogg_uint32_t entry=marker[length];
      
      /* when we claim a node for an entry, we also claim the nodes
	 below it (pruning off the imagined tree that may have dangled
	 from it) as well as blocking the use of any nodes directly
	 above for leaves */
      
      /* update ourself */
      if(length<32 && (entry>>length)){
	/* error condition; the lengths must specify an overpopulated tree */
	_ogg_free(r);
	return(NULL);
      }
      r[count++]=entry;
    
      /* Look to see if the next shorter marker points to the node
	 above. if so, update it and repeat.  */
      {
	for(j=length;j>0;j--){
	  
	  if(marker[j]&1){
	    /* have to jump branches */
	    if(j==1)
	      marker[1]++;
	    else
	      marker[j]=marker[j-1]<<1;
	    break; /* invariant says next upper marker would already
		      have been moved if it was on the same path */
	  }
	  marker[j]++;
	}
      }
      
      /* prune the tree; the implicit invariant says all the longer
	 markers were dangling from our just-taken node.  Dangle them
	 from our *new* node. */
      for(j=length+1;j<33;j++)
	if((marker[j]>>1) == entry){
	  entry=marker[j];
	  marker[j]=marker[j-1]<<1;
	}else
	  break;
    }else
      if(sparsecount==0)count++;
  }
    
  /* bitreverse the words because our bitwise packer/unpacker is LSb
     endian */
  for(i=0,count=0;i<n;i++){
    ogg_uint32_t temp=0;
    for(j=0;j<l[i];j++){
      temp<<=1;
      temp|=(r[count]>>j)&1;
    }

    if(sparsecount){
      if(l[i])
	r[count++]=temp;
    }else
      r[count++]=temp;
  }

  return(r);
}

/* there might be a straightforward one-line way to do the below
   that's portable and totally safe against roundoff, but I haven't
   thought of it.  Therefore, we opt on the side of caution */
long _book_maptype1_quantvals(const static_codebook *b){
  long vals=floor(pow((float)b->entries,1.f/b->dim));

  /* the above *should* be reliable, but we'll not assume that FP is
     ever reliable when bitstream sync is at stake; verify via integer
     means that vals really is the greatest value of dim for which
     vals^b->bim <= b->entries */
  /* treat the above as an initial guess */
  while(1){
    long acc=1;
    long acc1=1;
    int i;
    for(i=0;i<b->dim;i++){
      acc*=vals;
      acc1*=vals+1;
    }
    if(acc<=b->entries && acc1>b->entries){
      return(vals);
    }else{
      if(acc>b->entries){
	vals--;
      }else{
	vals++;
      }
    }
  }
}

/* unpack the quantized list of values for encode/decode ***********/
/* we need to deal with two map types: in map type 1, the values are
   generated algorithmically (each column of the vector counts through
   the values in the quant vector). in map type 2, all the values came
   in in an explicit list.  Both value lists must be unpacked */
FIXP *_book_unquantize(const static_codebook *b,int n,int *sparsemap){
  long j,k,count=0;
  if(b->maptype==1 || b->maptype==2){
    int quantvals;
    float mindel=_float32_unpack(b->q_min);
    float delta=_float32_unpack(b->q_delta);
    FIXP *r=_ogg_calloc(n*b->dim,sizeof(*r));

    /* maptype 1 and 2 both use a quantized value vector, but
       different sizes */
    switch(b->maptype){
    case 1:
      /* most of the time, entries%dimensions == 0, but we need to be
	 well defined.  We define that the possible vales at each
	 scalar is values == entries/dim.  If entries%dim != 0, we'll
	 have 'too few' values (values*dim<entries), which means that
	 we'll have 'left over' entries; left over entries use zeroed
	 values (and are wasted).  So don't generate codebooks like
	 that */
      quantvals=_book_maptype1_quantvals(b);
      for(j=0;j<b->entries;j++){
	if((sparsemap && b->lengthlist[j]) || !sparsemap){
	  float last=0.f;
	  int indexdiv=1;
	  for(k=0;k<b->dim;k++){
	    int index= (j/indexdiv)%quantvals;
	    float val=b->quantlist[index];
	    val=fabs(val)*delta+mindel+last;
	    if(b->q_sequencep)last=val;	  
	    if(sparsemap)
	      r[sparsemap[count]*b->dim+k]=TO_FIXP_CHK(16,val);
	    else
	      r[count*b->dim+k]=TO_FIXP_CHK(16,val);
	    indexdiv*=quantvals;
	  }
	  count++;
	}

      }
      break;
    case 2:
      for(j=0;j<b->entries;j++){
	if((sparsemap && b->lengthlist[j]) || !sparsemap){
	  float last=0.f;
	  
	  for(k=0;k<b->dim;k++){
	    float val=b->quantlist[j*b->dim+k];
	    val=fabs(val)*delta+mindel+last;
	    if(b->q_sequencep)last=val;	  
	    if(sparsemap)
	      r[sparsemap[count]*b->dim+k]=TO_FIXP_CHK(16,val);
	    else
	      r[count*b->dim+k]=TO_FIXP_CHK(16,val);
	  }
	  count++;
	}
      }
      break;
    }

    return(r);
  }
  return(NULL);
}

void vorbis_staticbook_clear(static_codebook *b){
  if(b->allocedp){
    if(b->quantlist)_ogg_free(b->quantlist);
    if(b->lengthlist)_ogg_free(b->lengthlist);
    if(b->nearest_tree){
      _ogg_free(b->nearest_tree->ptr0);
      _ogg_free(b->nearest_tree->ptr1);
      _ogg_free(b->nearest_tree->p);
      _ogg_free(b->nearest_tree->q);
      memset(b->nearest_tree,0,sizeof(*b->nearest_tree));
      _ogg_free(b->nearest_tree);
    }
    if(b->thresh_tree){
      _ogg_free(b->thresh_tree->quantthresh);
      _ogg_free(b->thresh_tree->quantmap);
      memset(b->thresh_tree,0,sizeof(*b->thresh_tree));
      _ogg_free(b->thresh_tree);
    }

    memset(b,0,sizeof(*b));
  }
}

void vorbis_staticbook_destroy(static_codebook *b){
  if(b->allocedp){
    vorbis_staticbook_clear(b);
    _ogg_free(b);
  }
}

void vorbis_book_clear(codebook *b){
  /* static book is not cleared; we're likely called on the lookup and
     the static codebook belongs to the info struct */
  if(b->valuelist)_ogg_free(b->valuelist);
  if(b->codelist)_ogg_free(b->codelist);

  if(b->dec_index)_ogg_free(b->dec_index);
  if(b->dec_codelengths)_ogg_free(b->dec_codelengths);
  if(b->dec_firsttable)_ogg_free(b->dec_firsttable);

  memset(b,0,sizeof(*b));
}

static ogg_uint32_t bitreverse(ogg_uint32_t x){
  x=    ((x>>16)&0x0000ffffUL) | ((x<<16)&0xffff0000UL);
  x=    ((x>> 8)&0x00ff00ffUL) | ((x<< 8)&0xff00ff00UL);
  x=    ((x>> 4)&0x0f0f0f0fUL) | ((x<< 4)&0xf0f0f0f0UL);
  x=    ((x>> 2)&0x33333333UL) | ((x<< 2)&0xccccccccUL);
  return((x>> 1)&0x55555555UL) | ((x<< 1)&0xaaaaaaaaUL);
}

static int sort32a(const void *a,const void *b){
  return ( (**(ogg_uint32_t **)a>**(ogg_uint32_t **)b)<<1)-1;
}

/* decode codebook arrangement is more heavily optimized than encode */
int vorbis_book_init_decode(codebook *c,const static_codebook *s){
  int i,j,n=0,tabn;
  int *sortindex;
  memset(c,0,sizeof(*c));
  
  /* count actually used entries */
  for(i=0;i<s->entries;i++)
    if(s->lengthlist[i]>0)
      n++;

  c->entries=s->entries;
  c->used_entries=n;
  c->dim=s->dim;

  /* two different remappings go on here.  

     First, we collapse the likely sparse codebook down only to
     actually represented values/words.  This collapsing needs to be
     indexed as map-valueless books are used to encode original entry
     positions as integers.

     Second, we reorder all vectors, including the entry index above,
     by sorted bitreversed codeword to allow treeless decode. */

  {
    /* perform sort */
    ogg_uint32_t *codes=_make_words(s->lengthlist,s->entries,c->used_entries);
    ogg_uint32_t **codep=alloca(sizeof(*codep)*n);
    
    if(codes==NULL)goto err_out;

    for(i=0;i<n;i++){
      codes[i]=bitreverse(codes[i]);
      codep[i]=codes+i;
    }

    qsort(codep,n,sizeof(*codep),sort32a);

    sortindex=alloca(n*sizeof(*sortindex));
    c->codelist=_ogg_malloc(n*sizeof(*c->codelist));
    /* the index is a reverse index */
    for(i=0;i<n;i++){
      int position=codep[i]-codes;
      sortindex[position]=i;
    }

    for(i=0;i<n;i++)
      c->codelist[sortindex[i]]=codes[i];
    _ogg_free(codes);
  }

  c->valuelist=_book_unquantize(s,n,sortindex);
  c->dec_index=_ogg_malloc(n*sizeof(*c->dec_index));

  for(n=0,i=0;i<s->entries;i++)
    if(s->lengthlist[i]>0)
      c->dec_index[sortindex[n++]]=i;
  
  c->dec_codelengths=_ogg_malloc(n*sizeof(*c->dec_codelengths));
  for(n=0,i=0;i<s->entries;i++)
    if(s->lengthlist[i]>0)
      c->dec_codelengths[sortindex[n++]]=s->lengthlist[i];

  c->dec_firsttablen=_ilog(c->used_entries)-4; /* this is magic */
  if(c->dec_firsttablen<5)c->dec_firsttablen=5;
  if(c->dec_firsttablen>8)c->dec_firsttablen=8;

  tabn=1<<c->dec_firsttablen;
  c->dec_firsttable=_ogg_calloc(tabn,sizeof(*c->dec_firsttable));
  c->dec_maxlength=0;

  for(i=0;i<n;i++){
    if(c->dec_maxlength<c->dec_codelengths[i])
      c->dec_maxlength=c->dec_codelengths[i];
    if(c->dec_codelengths[i]<=c->dec_firsttablen){
      ogg_uint32_t orig=bitreverse(c->codelist[i]);
      for(j=0;j<(1<<(c->dec_firsttablen-c->dec_codelengths[i]));j++)
	c->dec_firsttable[orig|(j<<c->dec_codelengths[i])]=i+1;
    }
  }

  /* now fill in 'unused' entries in the firsttable with hi/lo search
     hints for the non-direct-hits */
  {
    ogg_uint32_t mask=0xfffffffeUL<<(31-c->dec_firsttablen);
    long lo=0,hi=0;

    for(i=0;i<tabn;i++){
      ogg_uint32_t word=i<<(32-c->dec_firsttablen);
      if(c->dec_firsttable[bitreverse(word)]==0){
	while((lo+1)<n && c->codelist[lo+1]<=word)lo++;
	while(    hi<n && word>=(c->codelist[hi]&mask))hi++;
	
	/* we only actually have 15 bits per hint to play with here.
           In order to overflow gracefully (nothing breaks, efficiency
           just drops), encode as the difference from the extremes. */
	{
	  unsigned long loval=lo;
	  unsigned long hival=n-hi;

	  if(loval>0x7fff)loval=0x7fff;
	  if(hival>0x7fff)hival=0x7fff;
	  c->dec_firsttable[bitreverse(word)]=
	    0x80000000UL | (loval<<15) | hival;
	}
      }
    }
  }
  

  return(0);
 err_out:
  vorbis_book_clear(c);
  return(-1);
}