text: /********************************************************************
   *                                                                  *
   * THIS FILE IS PART OF THE OggVorbis 'TREMOR' 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 'TREMOR' SOURCE CODE IS (C) COPYRIGHT 1994-2003    *
   * BY THE Xiph.Org FOUNDATION http://www.xiph.org/                  *
   *                                                                  *
   ********************************************************************
  
   function: single-block PCM synthesis
   last mod: $Id$
  
   ********************************************************************/
  
  #include <stdio.h>
  #include "ogg.h"
  #include "ivorbiscodec.h"
  #include "codec_internal.h"
  #include "registry.h"
  #include "misc.h"
  #include "os.h"
  
  
  static inline int _vorbis_synthesis1(vorbis_block *vb,ogg_packet *op,int decodep){
    vorbis_dsp_state     *vd= vb ? vb->vd : 0;
    private_state        *b= vd ? (private_state *)vd->backend_state: 0;
    vorbis_info          *vi= vd ? vd->vi : 0;
    codec_setup_info     *ci= vi ? (codec_setup_info *)vi->codec_setup : 0;
    oggpack_buffer       *opb=vb ? &vb->opb : 0;
    int                   type,mode;
   
    if (!vd || !b || !vi || !ci || !opb) {
      return OV_EBADPACKET;
    }
  
    /* first things first.  Make sure decode is ready */
    _vorbis_block_ripcord(vb);
    oggpack_readinit(opb,op->packet,op->bytes);
  
    /* Check the packet type */
    if(oggpack_read(opb,1)!=0){
      /* Oops.  This is not an audio data packet */
      return(OV_ENOTAUDIO);
    }
  
    /* read our mode and pre/post windowsize */
    mode=oggpack_read(opb,b->modebits);
    if(mode==-1)return(OV_EBADPACKET);
    
    vb->mode=mode;
    if(!ci->mode_param[mode]){
      return(OV_EBADPACKET);
    }
  
    vb->W=ci->mode_param[mode]->blockflag;
    if(vb->W){
      vb->lW=oggpack_read(opb,1);
      vb->nW=oggpack_read(opb,1);
      if(vb->nW==-1)   return(OV_EBADPACKET);
    }else{
      vb->lW=0;
      vb->nW=0;
    }
    
    /* more setup */
    vb->granulepos=op->granulepos;
    vb->sequence=op->packetno-3; /* first block is third packet */
    vb->eofflag=op->e_o_s;
  
    if(decodep && vi->channels<=CHANNELS)
    {
      /* set pcm end point */
      vb->pcmend=ci->blocksizes[vb->W];
        
      /* unpack_header enforces range checking */
      type=ci->map_type[ci->mode_param[mode]->mapping];
      return(_mapping_P[type]->inverse(vb,b->mode[mode]));
    }else{
      /* no pcm */
      vb->pcmend=0;
      return(0);
    }
  }
  
  int vorbis_synthesis(vorbis_block *vb,ogg_packet *op)
    ICODE_ATTR_TREMOR_NOT_MDCT;
  int vorbis_synthesis(vorbis_block *vb,ogg_packet *op){
    return _vorbis_synthesis1(vb,op,1);
  }
  
  /* used to track pcm position without actually performing decode.
     Useful for sequential 'fast forward' */
  int vorbis_synthesis_trackonly(vorbis_block *vb,ogg_packet *op){
    return _vorbis_synthesis1(vb,op,0);
  }
  
  long vorbis_packet_blocksize(vorbis_info *vi,ogg_packet *op){
    codec_setup_info     *ci=(codec_setup_info *)vi->codec_setup;
    oggpack_buffer       opb;
    int                  mode;
   
    oggpack_readinit(&opb,op->packet,op->bytes);
  
    /* Check the packet type */
    if(oggpack_read(&opb,1)!=0){
      /* Oops.  This is not an audio data packet */
      return(OV_ENOTAUDIO);
    }
  
    {
      int modebits=0;
      int v=ci->modes;
      while(v>1){
        modebits++;
        v>>=1;
      }
  
      /* read our mode and pre/post windowsize */
      mode=oggpack_read(&opb,modebits);
    }
    if(mode==-1)return(OV_EBADPACKET);
    return(ci->blocksizes[ci->mode_param[mode]->blockflag]);
  }
  
  
  