avcodec/aacdec_template: Allow duplicated elements

Such streams are invalid according to
4.5.2.1 Top level payloads for the audio object types AAC main, AAC SSR, AAC LC and AAC LTP
4.5.2.1.1 Definitions
...cIn the raw_data_block(), several instances of the
same syntactic element may occur, but must have a different 4 bit
element_instance_tag, except for data_stream_element()'s and
fill_element()'s.

Fixes: Ticket7477
Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/aacdec_template.c

@@ -3161,12 +3161,15 @@ static int aac_decode_frame_int(AVCodecContext *avctx, void *data,
 
         if (elem_type < TYPE_DSE) {
             if (che_presence[elem_type][elem_id]) {
-                av_log(ac->avctx, AV_LOG_ERROR, "channel element %d.%d duplicate\n",
+                int error = che_presence[elem_type][elem_id] > 1;
+                av_log(ac->avctx, error ? AV_LOG_ERROR : AV_LOG_DEBUG, "channel element %d.%d duplicate\n",
                        elem_type, elem_id);
-                err = AVERROR_INVALIDDATA;
-                goto fail;
+                if (error) {
+                    err = AVERROR_INVALIDDATA;
+                    goto fail;
+                }
             }
-            che_presence[elem_type][elem_id] = 1;
+            che_presence[elem_type][elem_id]++;
 
             if (!(che=get_che(ac, elem_type, elem_id))) {
                 av_log(ac->avctx, AV_LOG_ERROR, "channel element %d.%d is not allocated\n",