Line data    Source code

       1             : /*====================================================================================
       2             :     EVS Codec 3GPP TS26.452 Aug 12, 2021. Version 16.3.0
       3             :   ====================================================================================*/
       4             : 
       5             : #include <stdint.h>
       6             : #include "options.h" /* Compilation switches                   */
       7             : #include "prot_fx.h" /* Function prototypes                    */
       8             : 
       9             : /*--------------------------------------------------------------------------
      10             :  * re8_dec_fx()
      11             :  *
      12             :  * MULTI-RATE INDEXING OF A POINT y in THE LATTICE RE8 (INDEX DECODING)
      13             :  * note: the index I is defined as a 32-bit word, but only
      14             :  * 16 bits are required (long can be replaced by unsigned integer)
      15             :  *--------------------------------------------------------------------------*/
      16             : 
      17     1637882 : void re8_dec_fx(
      18             :     Word16 n,         /* i  : codebook number (*n is an integer defined in {0,2,3,4,..,n_max})    */
      19             :     const UWord16 I,  /* i  : index of c (pointer to unsigned 16-bit word)                        */
      20             :     const Word16 k[], /* i  : index of v (8-dimensional vector of binary indices) = Voronoi index */
      21             :     Word16 y[]        /* o  : point in RE8 (8-dimensional integer vector)                         */
      22             : )
      23             : {
      24             :     Word16 i, m, v[8];
      25             : 
      26             :     /*------------------------------------------------------------------------*
      27             :      * decode the sub-indices I and kv[] according to the codebook number n:
      28             :      *  if n=0,2,3,4, decode I (no Voronoi extension)
      29             :      *  if n>4, Voronoi extension is used, decode I and kv[]
      30             :      *------------------------------------------------------------------------*/
      31     1637882 :     IF( LE_16( n, 4 ) )
      32             :     {
      33     1558219 :         re8_decode_base_index_fx( n, I, y );
      34             :     }
      35             :     ELSE
      36             :     {
      37             :         /*--------------------------------------------------------------------*
      38             :          * compute the Voronoi modulo m = 2^r where r is extension order
      39             :          *--------------------------------------------------------------------*/
      40       79663 :         m = 0;
      41       79663 :         move16();
      42             : 
      43      160850 :         FOR( ; n > 4; n -= 2 )
      44             :         {
      45       81187 :             m = add( m, 1 );
      46             :         }
      47             : 
      48             :         /*--------------------------------------------------------------------*
      49             :          * decode base codebook index I into c (c is an element of Q3 or Q4)
      50             :          *  [here c is stored in y to save memory]
      51             :          *--------------------------------------------------------------------*/
      52             : 
      53       79663 :         re8_decode_base_index_fx( n, I, y );
      54             : 
      55             :         /*--------------------------------------------------------------------*
      56             :          * decode Voronoi index k[] into v
      57             :          *--------------------------------------------------------------------*/
      58       79663 :         re8_k2y_fx( k, m, v );
      59             : 
      60             :         /*--------------------------------------------------------------------*
      61             :          * reconstruct y as y = m c + v (with m=2^r, r integer >=1)
      62             :          *--------------------------------------------------------------------*/
      63      716967 :         FOR( i = 0; i < 8; i++ )
      64             :         {
      65             :             /* y[i] = m*y[i] + v[i] */
      66      637304 :             y[i] = add( shl( y[i], m ), v[i] );
      67      637304 :             move16();
      68             :         }
      69             :     }
      70             : 
      71     1637882 :     return;
      72             : }