make exponent decoding consistent (prepare for merging coupling and lfe code...

make exponent decoding consistent (prepare for merging coupling and lfe code with normal channel code).

Originally committed as revision 9904 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/ac3dec.c

@@ -697,12 +697,11 @@ static int ac3_parse_audio_block(AC3DecodeContext *ctx, int blk)
 {
     int nfchans = ctx->nfchans;
     int acmod = ctx->acmod;
-    int i, bnd, seg, grpsize, ch;
+    int i, bnd, seg, ch;
     GetBitContext *gb = &ctx->gb;
     int bit_alloc_flags = 0;
-    int8_t *dexps;
     int mstrcplco, cplcoexp, cplcomant;
-    int chbwcod, ngrps, cplabsexp, skipl;
+    int chbwcod, skipl;
 
     for (i = 0; i < nfchans; i++) /*block switch flag */
         ctx->blksw[i] = get_bits1(gb);
@@ -827,28 +826,32 @@ static int ac3_parse_audio_block(AC3DecodeContext *ctx, int blk)
     }
 
     if (ctx->cplexpstr != EXP_REUSE) {/* coupling exponents */
+        int grpsize, ngrps, absexp;
         bit_alloc_flags = 64;
-        cplabsexp = get_bits(gb, 4) << 1;
-        ngrps = (ctx->cplendmant - ctx->cplstrtmant) / (3 << (ctx->cplexpstr - 1));
-        decode_exponents(gb, ctx->cplexpstr, ngrps, cplabsexp, ctx->dcplexps + ctx->cplstrtmant);
+        grpsize = 3 << (ctx->cplexpstr - 1);
+        ngrps = (ctx->cplendmant - ctx->cplstrtmant) / grpsize;
+        absexp = get_bits(gb, 4) << 1;
+        decode_exponents(gb, ctx->cplexpstr, ngrps, absexp, &ctx->dcplexps[ctx->cplstrtmant]);
     }
 
     for (i = 0; i < nfchans; i++) { /* fbw channel exponents */
         if (ctx->chexpstr[i] != EXP_REUSE) {
+            int grpsize, ngrps, absexp;
             bit_alloc_flags |= 1 << i;
             grpsize = 3 << (ctx->chexpstr[i] - 1);
             ngrps = (ctx->endmant[i] + grpsize - 4) / grpsize;
-            dexps = ctx->dexps[i];
-            dexps[0] = get_bits(gb, 4);
-            decode_exponents(gb, ctx->chexpstr[i], ngrps, dexps[0], dexps + 1);
+            absexp = ctx->dexps[i][0] = get_bits(gb, 4);
+            decode_exponents(gb, ctx->chexpstr[i], ngrps, absexp, &ctx->dexps[i][1]);
             skip_bits(gb, 2); /* skip gainrng */
         }
     }
 
     if (ctx->lfeexpstr != EXP_REUSE) { /* lfe exponents */
+        int ngrps, absexp;
         bit_alloc_flags |= 32;
-        ctx->dlfeexps[0] = get_bits(gb, 4);
-        decode_exponents(gb, ctx->lfeexpstr, 2, ctx->dlfeexps[0], ctx->dlfeexps + 1);
+        ngrps = 2;
+        absexp = ctx->dlfeexps[0] = get_bits(gb, 4);
+        decode_exponents(gb, ctx->lfeexpstr, ngrps, absexp, &ctx->dlfeexps[1]);
     }
 
     if (get_bits1(gb)) { /* bit allocation information */