aac: Correctly map multichannel ADTS AAC with non-zero channel_config + PCE

The decoder assigns channels using default channel configuration
for 5.1ch when it parses an ADTS frame header using consecutive
channel ids.

When a PCE comes, it reassigns channels using PCE configuration
using directly the ids provided. They can be arbitrary.

Always use consecutive channel ids to avoid decoding glitches due
spurious reconfigurations due the channel ids mismatch between the
two otherwise-identical channel maps.
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

libavcodec/aacdec.c

@@ -443,12 +443,18 @@ static int output_configure(AACContext *ac,
     AVCodecContext *avctx = ac->avctx;
     int i, channels = 0, ret;
     uint64_t layout = 0;
+    uint8_t id_map[TYPE_END][MAX_ELEM_ID] = {{ 0 }};
+    uint8_t type_counts[TYPE_END] = { 0 };
 
     if (ac->oc[1].layout_map != layout_map) {
         memcpy(ac->oc[1].layout_map, layout_map, tags * sizeof(layout_map[0]));
         ac->oc[1].layout_map_tags = tags;
     }
-
+    for (i = 0; i < tags; i++) {
+        int type =         layout_map[i][0];
+        int id =           layout_map[i][1];
+        id_map[type][id] = type_counts[type]++;
+    }
     // Try to sniff a reasonable channel order, otherwise output the
     // channels in the order the PCE declared them.
     if (avctx->request_channel_layout != AV_CH_LAYOUT_NATIVE)
@@ -456,12 +462,14 @@ static int output_configure(AACContext *ac,
     for (i = 0; i < tags; i++) {
         int type =     layout_map[i][0];
         int id =       layout_map[i][1];
+        int iid =      id_map[type][id];
         int position = layout_map[i][2];
         // Allocate or free elements depending on if they are in the
         // current program configuration.
-        ret = che_configure(ac, position, type, id, &channels);
+        ret = che_configure(ac, position, type, iid, &channels);
         if (ret < 0)
             return ret;
+        ac->tag_che_map[type][id] = ac->che[type][iid];
     }
     if (ac->oc[1].m4ac.ps == 1 && channels == 2) {
         if (layout == AV_CH_FRONT_CENTER) {
@@ -471,7 +479,6 @@ static int output_configure(AACContext *ac,
         }
     }
 
-    memcpy(ac->tag_che_map, ac->che, 4 * MAX_ELEM_ID * sizeof(ac->che[0][0]));
     avctx->channel_layout = ac->oc[1].channel_layout = layout;
     avctx->channels       = ac->oc[1].channels       = channels;
     ac->oc[1].status = oc_type;