shithub: opus

Download patch

ref: 017001a512c0152641aeaa561d56475a62c6f58b
parent: 8cbea177ba1a99c36d15adda77f615f8e80fe212
author: Jean-Marc Valin <[email protected]>
date: Thu Aug 5 11:42:50 EDT 2010 

Simplified flags encoding


--- a/libcelt/celt.c
+++ b/libcelt/celt.c
@@ -400,74 +400,6 @@
    }
 }
 
-#define FLAG_NONE        0
-#define FLAG_INTRA       (1U<<13)
-#define FLAG_PITCH       (1U<<12)
-#define FLAG_SHORT       (1U<<11)
-#define FLAG_FOLD        (1U<<10)
-#define FLAG_MASK        (FLAG_INTRA|FLAG_PITCH|FLAG_SHORT|FLAG_FOLD)
-
-static const int flaglist[8] = {
-      0 /*00  */ | FLAG_FOLD,
-      1 /*01  */ | FLAG_PITCH|FLAG_FOLD,
-      8 /*1000*/ | FLAG_NONE,
-      9 /*1001*/ | FLAG_SHORT|FLAG_FOLD,
-     10 /*1010*/ | FLAG_PITCH,
-     11 /*1011*/ | FLAG_INTRA,
-      6 /*110 */ | FLAG_INTRA|FLAG_FOLD,
-      7 /*111 */ | FLAG_INTRA|FLAG_SHORT|FLAG_FOLD
-};
-
-static void encode_flags(ec_enc *enc, int intra_ener, int shortBlocks, int has_fold)
-{
-   int i;
-   int flags=FLAG_NONE;
-   int flag_bits;
-   flags |= intra_ener   ? FLAG_INTRA : 0;
-   flags |= shortBlocks  ? FLAG_SHORT : 0;
-   flags |= has_fold     ? FLAG_FOLD  : 0;
-   for (i=0;i<8;i++)
-   {
-      if (flags == (flaglist[i]&FLAG_MASK))
-      {
-         flag_bits = flaglist[i]&0xf;
-         break;
-      }
-   }
-   celt_assert(i<8);
-   /*printf ("enc %d: %d %d %d %d\n", flag_bits, intra_ener, has_pitch, shortBlocks, has_fold);*/
-   if (i<2)
-      ec_enc_uint(enc, flag_bits, 4);
-   else if (i<6)
-   {
-      ec_enc_uint(enc, flag_bits>>2, 4);
-      ec_enc_uint(enc, flag_bits&0x3, 4);
-   } else {
-      ec_enc_uint(enc, flag_bits>>1, 4);
-      ec_enc_uint(enc, flag_bits&0x1, 2);
-   }
-}
-
-static void decode_flags(ec_dec *dec, int *intra_ener, int *shortBlocks, int *has_fold)
-{
-   int i;
-   int flag_bits;
-   flag_bits = ec_dec_uint(dec, 4);
-   /*printf ("(%d) ", flag_bits);*/
-   if (flag_bits==2)
-      flag_bits = (flag_bits<<2) | ec_dec_uint(dec, 4);
-   else if (flag_bits==3)
-      flag_bits = (flag_bits<<1) | ec_dec_uint(dec, 2);
-   for (i=0;i<8;i++)
-      if (flag_bits == (flaglist[i]&0xf))
-         break;
-   celt_assert(i<8);
-   *intra_ener  = (flaglist[i]&FLAG_INTRA) != 0;
-   *shortBlocks = (flaglist[i]&FLAG_SHORT) != 0;
-   *has_fold    = (flaglist[i]&FLAG_FOLD ) != 0;
-   /*printf ("dec %d: %d %d %d %d\n", flag_bits, *intra_ener, *has_pitch, *shortBlocks, *has_fold);*/
-}
-
 static void deemphasis(celt_sig *in, celt_word16 *pcm, int N, int _C, const celt_word16 *coef, celt_sig *mem)
 {
    const int C = CHANNELS(_C);
@@ -877,8 +809,12 @@
          mdct_shape(st->mode, X, mdct_weight_pos+1, M, N, mdct_weight_shift, effEnd, C, 0, M);
    }
 
+   /* Encode the global flags using a simple probability model
+      (first symbols in the stream) */
+   ec_enc_bit_prob(enc, intra_ener, 8192);
+   ec_enc_bit_prob(enc, shortBlocks!=0, 8192);
+   ec_enc_bit_prob(enc, has_fold, 57344);
 
-   encode_flags(enc, intra_ener, shortBlocks, has_fold);
    if (shortBlocks)
    {
       if (transient_shift)
@@ -1676,7 +1612,11 @@
    }
    nbAvailableBytes = len-nbFilledBytes;
 
-   decode_flags(dec, &intra_ener, &isTransient, &has_fold);
+   /* Decode the global flags (first symbols in the stream) */
+   intra_ener = ec_dec_bit_prob(dec, 8192);
+   isTransient = ec_dec_bit_prob(dec, 8192);
+   has_fold = ec_dec_bit_prob(dec, 57344);
+
    if (isTransient)
       shortBlocks = M;
    else