source: downloads/libvorbis-1.2.0/lib/envelope.c @ 52

/********************************************************************
 *                                                                  *
 * 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 1994-2007             *
 * by the Xiph.Org Foundation http://www.xiph.org/                  *
 *                                                                  *
 ********************************************************************

 function: PCM data envelope analysis 
 last mod: $Id: envelope.c 13293 2007-07-24 00:09:47Z xiphmont $

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

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <math.h>
#include <ogg/ogg.h>
#include "vorbis/codec.h"
#include "codec_internal.h"

#include "os.h"
#include "scales.h"
#include "envelope.h"
#include "mdct.h"
#include "misc.h"

void _ve_envelope_init(envelope_lookup *e,vorbis_info *vi){
  codec_setup_info *ci=vi->codec_setup;
  vorbis_info_psy_global *gi=&ci->psy_g_param;
  int ch=vi->channels;
  int i,j;
  int n=e->winlength=128;
  e->searchstep=64; /* not random */

  e->minenergy=gi->preecho_minenergy;
  e->ch=ch;
  e->storage=128;
  e->cursor=ci->blocksizes[1]/2;
  e->mdct_win=_ogg_calloc(n,sizeof(*e->mdct_win));
  mdct_init(&e->mdct,n);

  for(i=0;i<n;i++){
    e->mdct_win[i]=sin(i/(n-1.)*M_PI);
    e->mdct_win[i]*=e->mdct_win[i];
  }

  /* magic follows */
  e->band[0].begin=2;  e->band[0].end=4;
  e->band[1].begin=4;  e->band[1].end=5;
  e->band[2].begin=6;  e->band[2].end=6;
  e->band[3].begin=9;  e->band[3].end=8;
  e->band[4].begin=13;  e->band[4].end=8;
  e->band[5].begin=17;  e->band[5].end=8;
  e->band[6].begin=22;  e->band[6].end=8;

  for(j=0;j<VE_BANDS;j++){
    n=e->band[j].end;
    e->band[j].window=_ogg_malloc(n*sizeof(*e->band[0].window));
    for(i=0;i<n;i++){
      e->band[j].window[i]=sin((i+.5)/n*M_PI);
      e->band[j].total+=e->band[j].window[i];
    }
    e->band[j].total=1./e->band[j].total;
  }
  
  e->filter=_ogg_calloc(VE_BANDS*ch,sizeof(*e->filter));
  e->mark=_ogg_calloc(e->storage,sizeof(*e->mark));

}

void _ve_envelope_clear(envelope_lookup *e){
  int i;
  mdct_clear(&e->mdct);
  for(i=0;i<VE_BANDS;i++)
    _ogg_free(e->band[i].window);
  _ogg_free(e->mdct_win);
  _ogg_free(e->filter);
  _ogg_free(e->mark);
  memset(e,0,sizeof(*e));
}

/* fairly straight threshhold-by-band based until we find something
   that works better and isn't patented. */

static int _ve_amp(envelope_lookup *ve,
                   vorbis_info_psy_global *gi,
                   float *data,
                   envelope_band *bands,
                   envelope_filter_state *filters,
                   long pos){
  long n=ve->winlength;
  int ret=0;
  long i,j;
  float decay;

  /* we want to have a 'minimum bar' for energy, else we're just
     basing blocks on quantization noise that outweighs the signal
     itself (for low power signals) */

  float minV=ve->minenergy;
  float *vec=alloca(n*sizeof(*vec));

  /* stretch is used to gradually lengthen the number of windows
     considered prevoius-to-potential-trigger */
  int stretch=max(VE_MINSTRETCH,ve->stretch/2);
  float penalty=gi->stretch_penalty-(ve->stretch/2-VE_MINSTRETCH);
  if(penalty<0.f)penalty=0.f;
  if(penalty>gi->stretch_penalty)penalty=gi->stretch_penalty;
  
  /*_analysis_output_always("lpcm",seq2,data,n,0,0,
    totalshift+pos*ve->searchstep);*/
  
 /* window and transform */
  for(i=0;i<n;i++)
    vec[i]=data[i]*ve->mdct_win[i];
  mdct_forward(&ve->mdct,vec,vec);
  
  /*_analysis_output_always("mdct",seq2,vec,n/2,0,1,0); */

  /* near-DC spreading function; this has nothing to do with
     psychoacoustics, just sidelobe leakage and window size */
  {
    float temp=vec[0]*vec[0]+.7*vec[1]*vec[1]+.2*vec[2]*vec[2];
    int ptr=filters->nearptr;

    /* the accumulation is regularly refreshed from scratch to avoid
       floating point creep */
    if(ptr==0){
      decay=filters->nearDC_acc=filters->nearDC_partialacc+temp;
      filters->nearDC_partialacc=temp;
    }else{
      decay=filters->nearDC_acc+=temp;
      filters->nearDC_partialacc+=temp;
    }
    filters->nearDC_acc-=filters->nearDC[ptr];
    filters->nearDC[ptr]=temp;

    decay*=(1./(VE_NEARDC+1));
    filters->nearptr++;
    if(filters->nearptr>=VE_NEARDC)filters->nearptr=0;
    decay=todB(&decay)*.5-15.f;
  }
  
  /* perform spreading and limiting, also smooth the spectrum.  yes,
     the MDCT results in all real coefficients, but it still *behaves*
     like real/imaginary pairs */
  for(i=0;i<n/2;i+=2){
    float val=vec[i]*vec[i]+vec[i+1]*vec[i+1];
    val=todB(&val)*.5f;
    if(val<decay)val=decay;
    if(val<minV)val=minV;
    vec[i>>1]=val;
    decay-=8.;
  }

  /*_analysis_output_always("spread",seq2++,vec,n/4,0,0,0);*/
  
  /* perform preecho/postecho triggering by band */
  for(j=0;j<VE_BANDS;j++){
    float acc=0.;
    float valmax,valmin;

    /* accumulate amplitude */
    for(i=0;i<bands[j].end;i++)
      acc+=vec[i+bands[j].begin]*bands[j].window[i];
   
    acc*=bands[j].total;

    /* convert amplitude to delta */
    {
      int p,this=filters[j].ampptr;
      float postmax,postmin,premax=-99999.f,premin=99999.f;
      
      p=this;
      p--;
      if(p<0)p+=VE_AMP;
      postmax=max(acc,filters[j].ampbuf[p]);
      postmin=min(acc,filters[j].ampbuf[p]);
      
      for(i=0;i<stretch;i++){
        p--;
        if(p<0)p+=VE_AMP;
        premax=max(premax,filters[j].ampbuf[p]);
        premin=min(premin,filters[j].ampbuf[p]);
      }
      
      valmin=postmin-premin;
      valmax=postmax-premax;

      /*filters[j].markers[pos]=valmax;*/
      filters[j].ampbuf[this]=acc;
      filters[j].ampptr++;
      if(filters[j].ampptr>=VE_AMP)filters[j].ampptr=0;
    }

    /* look at min/max, decide trigger */
    if(valmax>gi->preecho_thresh[j]+penalty){
      ret|=1;
      ret|=4;
    }
    if(valmin<gi->postecho_thresh[j]-penalty)ret|=2;
  }
 
  return(ret);
}

#if 0
static int seq=0;
static ogg_int64_t totalshift=-1024;
#endif

long _ve_envelope_search(vorbis_dsp_state *v){
  vorbis_info *vi=v->vi;
  codec_setup_info *ci=vi->codec_setup;
  vorbis_info_psy_global *gi=&ci->psy_g_param;
  envelope_lookup *ve=((private_state *)(v->backend_state))->ve;
  long i,j;

  int first=ve->current/ve->searchstep;
  int last=v->pcm_current/ve->searchstep-VE_WIN;
  if(first<0)first=0;

  /* make sure we have enough storage to match the PCM */
  if(last+VE_WIN+VE_POST>ve->storage){
    ve->storage=last+VE_WIN+VE_POST; /* be sure */
    ve->mark=_ogg_realloc(ve->mark,ve->storage*sizeof(*ve->mark));
  }

  for(j=first;j<last;j++){
    int ret=0;

    ve->stretch++;
    if(ve->stretch>VE_MAXSTRETCH*2)
      ve->stretch=VE_MAXSTRETCH*2;
    
    for(i=0;i<ve->ch;i++){
      float *pcm=v->pcm[i]+ve->searchstep*(j);
      ret|=_ve_amp(ve,gi,pcm,ve->band,ve->filter+i*VE_BANDS,j);
    }

    ve->mark[j+VE_POST]=0;
    if(ret&1){
      ve->mark[j]=1;
      ve->mark[j+1]=1;
    }

    if(ret&2){
      ve->mark[j]=1;
      if(j>0)ve->mark[j-1]=1;
    }

    if(ret&4)ve->stretch=-1;
  }

  ve->current=last*ve->searchstep;

  {
    long centerW=v->centerW;
    long testW=
      centerW+
      ci->blocksizes[v->W]/4+
      ci->blocksizes[1]/2+
      ci->blocksizes[0]/4;
    
    j=ve->cursor;
    
    while(j<ve->current-(ve->searchstep)){/* account for postecho
                                             working back one window */
      if(j>=testW)return(1);
 
      ve->cursor=j;

      if(ve->mark[j/ve->searchstep]){
        if(j>centerW){

#if 0
          if(j>ve->curmark){
            float *marker=alloca(v->pcm_current*sizeof(*marker));
            int l,m;
            memset(marker,0,sizeof(*marker)*v->pcm_current);
            fprintf(stderr,"mark! seq=%d, cursor:%fs time:%fs\n",
                    seq,
                    (totalshift+ve->cursor)/44100.,
                    (totalshift+j)/44100.);
            _analysis_output_always("pcmL",seq,v->pcm[0],v->pcm_current,0,0,totalshift);
            _analysis_output_always("pcmR",seq,v->pcm[1],v->pcm_current,0,0,totalshift);

            _analysis_output_always("markL",seq,v->pcm[0],j,0,0,totalshift);
            _analysis_output_always("markR",seq,v->pcm[1],j,0,0,totalshift);
            
            for(m=0;m<VE_BANDS;m++){
              char buf[80];
              sprintf(buf,"delL%d",m);
              for(l=0;l<last;l++)marker[l*ve->searchstep]=ve->filter[m].markers[l]*.1;
              _analysis_output_always(buf,seq,marker,v->pcm_current,0,0,totalshift);
            }

            for(m=0;m<VE_BANDS;m++){
              char buf[80];
              sprintf(buf,"delR%d",m);
              for(l=0;l<last;l++)marker[l*ve->searchstep]=ve->filter[m+VE_BANDS].markers[l]*.1;
              _analysis_output_always(buf,seq,marker,v->pcm_current,0,0,totalshift);
            }

            for(l=0;l<last;l++)marker[l*ve->searchstep]=ve->mark[l]*.4;
            _analysis_output_always("mark",seq,marker,v->pcm_current,0,0,totalshift);
           
            
            seq++;
            
          }
#endif

          ve->curmark=j;
          if(j>=testW)return(1);
          return(0);
        }
      }
      j+=ve->searchstep;
    }
  }
  
  return(-1);
}

int _ve_envelope_mark(vorbis_dsp_state *v){
  envelope_lookup *ve=((private_state *)(v->backend_state))->ve;
  vorbis_info *vi=v->vi;
  codec_setup_info *ci=vi->codec_setup;
  long centerW=v->centerW;
  long beginW=centerW-ci->blocksizes[v->W]/4;
  long endW=centerW+ci->blocksizes[v->W]/4;
  if(v->W){
    beginW-=ci->blocksizes[v->lW]/4;
    endW+=ci->blocksizes[v->nW]/4;
  }else{
    beginW-=ci->blocksizes[0]/4;
    endW+=ci->blocksizes[0]/4;
  }

  if(ve->curmark>=beginW && ve->curmark<endW)return(1);
  {
    long first=beginW/ve->searchstep;
    long last=endW/ve->searchstep;
    long i;
    for(i=first;i<last;i++)
      if(ve->mark[i])return(1);
  }
  return(0);
}

void _ve_envelope_shift(envelope_lookup *e,long shift){
  int smallsize=e->current/e->searchstep+VE_POST; /* adjust for placing marks
                                                     ahead of ve->current */
  int smallshift=shift/e->searchstep;

  memmove(e->mark,e->mark+smallshift,(smallsize-smallshift)*sizeof(*e->mark));
  
#if 0
  for(i=0;i<VE_BANDS*e->ch;i++)
    memmove(e->filter[i].markers,
            e->filter[i].markers+smallshift,
            (1024-smallshift)*sizeof(*(*e->filter).markers));
  totalshift+=shift;
#endif 

  e->current-=shift;
  if(e->curmark>=0)
    e->curmark-=shift;
  e->cursor-=shift;
}