avformat/avformat: use the side data from AVStream.codecpar

Deprecate AVStream.side_data and its helpers in favor of the AVStream's
codecpar.coded_side_data.

This will considerably simplify the propagation of global side data to decoders
and from encoders. Instead of having to do it inside packets, it will be
available during init().
Global and frame specific side data will therefore be distinct.

Signed-off-by: James Almer <jamrial@gmail.com>

libavformat/mux.c

@@ -279,6 +279,27 @@ FF_ENABLE_DEPRECATION_WARNINGS
             break;
         }
 
+#if FF_API_AVSTREAM_SIDE_DATA
+FF_DISABLE_DEPRECATION_WARNINGS
+        /* if the caller is using the deprecated AVStream side_data API,
+         * copy its contents to AVStream.codecpar, giving it priority
+           over existing side data in the latter */
+        for (int i = 0; i < st->nb_side_data; i++) {
+            const AVPacketSideData *sd_src = &st->side_data[i];
+            AVPacketSideData *sd_dst;
+
+            sd_dst = av_packet_side_data_new(&st->codecpar->coded_side_data,
+                                             &st->codecpar->nb_coded_side_data,
+                                             sd_src->type, sd_src->size, 0);
+            if (!sd_dst) {
+                ret = AVERROR(ENOMEM);
+                goto fail;
+            }
+            memcpy(sd_dst->data, sd_src->data, sd_src->size);
+        }
+FF_ENABLE_DEPRECATION_WARNINGS
+#endif
+
         desc = avcodec_descriptor_get(par->codec_id);
         if (desc && desc->props & AV_CODEC_PROP_REORDER)
             sti->reorder = 1;