Modify decode_band_structure() so that the actual band structure is only

used within the function.  This removes the need to have the coupling band 
structure stored in the AC3DecodeContext.


git-svn-id: file:///var/local/repositories/ffmpeg/trunk@19585 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/ac3dec.c

@@ -724,32 +724,34 @@ static void ac3_upmix_delay(AC3DecodeContext *s)
  * @param[in] start_subband subband number for start of range
  * @param[in] end_subband subband number for end of range
  * @param[in] default_band_struct default band structure table
- * @param[out] band_struct decoded band structure
  * @param[out] num_bands number of bands (optionally NULL)
  * @param[out] band_sizes array containing the number of bins in each band (optionally NULL)
  */
 static void decode_band_structure(GetBitContext *gbc, int blk, int eac3,
                                   int ecpl, int start_subband, int end_subband,
                                   const uint8_t *default_band_struct,
-                                  uint8_t *band_struct, int *num_bands,
+                                  int *num_bands,
                                   uint8_t *band_sizes)
 {
     int subbnd, bnd, n_subbands, n_bands=0;
     uint8_t bnd_sz[22];
+    uint8_t coded_band_struct[22];
+    const uint8_t *band_struct;
 
     n_subbands = end_subband - start_subband;
 
     /* decode band structure from bitstream or use default */
     if (!eac3 || get_bits1(gbc)) {
         for (subbnd = 0; subbnd < n_subbands - 1; subbnd++) {
-            band_struct[subbnd] = get_bits1(gbc);
+            coded_band_struct[subbnd] = get_bits1(gbc);
         }
+        band_struct = coded_band_struct;
     } else if (!blk) {
-        memcpy(band_struct,
-               &default_band_struct[start_subband+1],
-               n_subbands-1);
+        band_struct = &default_band_struct[start_subband+1];
+    } else {
+        /* no change in band structure */
+        return;
     }
-    band_struct[n_subbands-1] = 0;
 
     /* calculate number of bands and band sizes based on band structure.
        note that the first 4 subbands in enhanced coupling span only 6 bins
@@ -879,7 +881,7 @@ static int decode_audio_block(AC3DecodeContext *s, int blk)
             decode_band_structure(gbc, blk, s->eac3, 0, cpl_start_subband,
                                   cpl_end_subband,
                                   ff_eac3_default_cpl_band_struct,
-                                  s->cpl_band_struct, &s->num_cpl_bands,
+                                  &s->num_cpl_bands,
                                   s->cpl_band_sizes);
         } else {
             /* coupling not in use */

libavcodec/ac3dec.h

@@ -82,7 +82,6 @@ typedef struct {
     int phase_flags_in_use;                 ///< phase flags in use                     (phsflginu)
     int phase_flags[18];                    ///< phase flags                            (phsflg)
     int num_cpl_bands;                      ///< number of coupling bands               (ncplbnd)
-    uint8_t cpl_band_struct[18];            ///< coupling band structure                (cplbndstrc)
     uint8_t cpl_band_sizes[18];             ///< number of coeffs in each coupling band
     int firstchincpl;                       ///< first channel in coupling
     int first_cpl_coords[AC3_MAX_CHANNELS]; ///< first coupling coordinates states      (firstcplcos)