www.pudn.com > aacenc.rar > mc_enc.c

/******************************************************************************************* 
 * 
 * Multichannel allocation module. 
 * 
 * Authors: 
 * CL    Chuck Lueck, TI  
 * RG    Ralf Geiger, FhG/IIS 
 * 
 * Changes: 
 * 22-jan-98   CL   Initial revision. 
 * 07-apr-98   RG   Added determination of LFE channel. 
 ***************************************************************************************/ 
 
#include "mc_enc.h" 
 
void DetermineChInfo(Ch_Info* chInfo, int numChannels) { 
    
  /* If LFE present                                                       */ 
  /*  Num channels       # of SCE's       # of CPE's       #of LFE's      */  
  /*  ============       ==========       ==========       =========      */ 
  /*      1                  1                0               0           */ 
  /*      2                  0                1               0           */ 
  /*      3                  1                1               0           */ 
  /*      4                  1                1               1           */ 
  /*      5                  1                2               0           */ 
  /* For more than 5 channels, use the following elements:                */ 
  /*      2*N                1                2*(N-1)         1           */ 
  /*      2*N+1              1                2*N             0           */ 
  /*                                                                      */ 
  /* Else:                                                                */ 
  /*                                                                      */   
  /*  Num channels       # of SCE's       # of CPE's       #of LFE's      */ 
  /*  ============       ==========       ==========       =========      */ 
  /*      1                  1                0               0           */ 
  /*      2                  0                1               0           */ 
  /*      3                  1                1               0           */ 
  /*      4                  2                1               0           */ 
  /*      5                  1                2               0           */ 
  /* For more than 5 channels, use the following elements:                */ 
  /*      2*N                2                2*(N-1)         0           */ 
  /*      2*N+1              1                2*N             0           */ 
 
  int sceTag=0; 
  int cpeTag=0; 
  int numChannelsLeft=numChannels; 
 
  
  /* First element is sce, except for 2 channel case */ 
  if (numChannelsLeft!=2) { 
    chInfo[numChannels-numChannelsLeft].present = 1; 
    chInfo[numChannels-numChannelsLeft].tag=sceTag++; 
    chInfo[numChannels-numChannelsLeft].cpe=0; 
    numChannelsLeft--; 
  } 
 
  /* Next elements are cpe's */ 
  while (numChannelsLeft>1) { 
    /* Left channel info */ 
    chInfo[numChannels-numChannelsLeft].present = 1; 
    chInfo[numChannels-numChannelsLeft].tag=cpeTag++; 
    chInfo[numChannels-numChannelsLeft].cpe=1; 
    chInfo[numChannels-numChannelsLeft].common_window=0; 
    chInfo[numChannels-numChannelsLeft].ch_is_left=1; 
    chInfo[numChannels-numChannelsLeft].paired_ch=numChannels-numChannelsLeft+1; 
    numChannelsLeft--; 
   
    /* Right channel info */ 
    chInfo[numChannels-numChannelsLeft].present = 1; 
    chInfo[numChannels-numChannelsLeft].cpe=1; 
    chInfo[numChannels-numChannelsLeft].common_window=0; 
    chInfo[numChannels-numChannelsLeft].ch_is_left=0; 
    chInfo[numChannels-numChannelsLeft].paired_ch=numChannels-numChannelsLeft-1; 
    numChannelsLeft--; 
  } 
   
  /* Is there another channel left ? */ 
  if (numChannelsLeft) { 
      chInfo[numChannels-numChannelsLeft].present = 1; 
      chInfo[numChannels-numChannelsLeft].tag=sceTag++; 
      chInfo[numChannels-numChannelsLeft].cpe=0; 
    numChannelsLeft--; 
  } 
}