ac3enc: fix encoding of stereo ac3 files when rematrixing is disabled.

The number of rematrixing bands still needs to be calculated.

libavcodec/ac3enc_template.c

@@ -352,11 +352,6 @@ static void compute_rematrixing_strategy(AC3EncodeContext *s)
         block = &s->blocks[blk];
         block->new_rematrixing_strategy = !blk;
 
-        if (!s->rematrixing_enabled) {
-            block0 = block;
-            continue;
-        }
-
         block->num_rematrixing_bands = 4;
         if (block->cpl_in_use) {
             block->num_rematrixing_bands -= (s->start_freq[CPL_CH] <= 61);
@@ -366,6 +361,11 @@ static void compute_rematrixing_strategy(AC3EncodeContext *s)
         }
         nb_coefs = FFMIN(block->end_freq[1], block->end_freq[2]);
 
+        if (!s->rematrixing_enabled) {
+            block0 = block;
+            continue;
+        }
+
         for (bnd = 0; bnd < block->num_rematrixing_bands; bnd++) {
             /* calculate calculate sum of squared coeffs for one band in one block */
             int start = ff_ac3_rematrix_band_tab[bnd];