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.

Originally committed as revision 19585 to svn://svn.ffmpeg.org/ffmpeg/trunk

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)