@@ -113,6 +113,22 @@ static const char overread_err[] = "Input buffer exhausted before END element fo

 static ChannelElement *get_che(AACContext *ac, int type, int elem_id)

 {

+    /* Some buggy encoders appear to set all elem_ids to zero and rely on

+    channels always occurring in the same order. This is expressly forbidden

+    by the spec but we will try to work around it.

+    */

+    int err_printed = 0;

+    while (ac->tags_seen_this_frame[type][elem_id] && elem_id < MAX_ELEM_ID) {

+        if (ac->output_configured < OC_LOCKED && !err_printed) {

+            av_log(ac->avccontext, AV_LOG_WARNING, "Duplicate channel tag found, attempting to remap.\n");

+            err_printed = 1;

+        }

+        elem_id++;

+    }

+    if (elem_id == MAX_ELEM_ID)

+        return NULL;

+    ac->tags_seen_this_frame[type][elem_id] = 1;

+

     if (ac->tag_che_map[type][elem_id]) {

         return ac->tag_che_map[type][elem_id];

     }

@@ -1969,6 +1985,7 @@ static int aac_decode_frame(AVCodecContext *avccontext, void *data,

         }

     }

+    memset(ac->tags_seen_this_frame, 0, sizeof(ac->tags_seen_this_frame));

     // parse

     while ((elem_type = get_bits(&gb, 3)) != TYPE_END) {

         elem_id = get_bits(&gb, 4);

@@ -257,6 +257,7 @@ typedef struct {

                                                    */

     ChannelElement * che[4][MAX_ELEM_ID];

     ChannelElement * tag_che_map[4][MAX_ELEM_ID];

+    uint8_t tags_seen_this_frame[4][MAX_ELEM_ID];

     int tags_mapped;

     /** @} */