avformat/dashenc: Reduce Muxing overhead for chunked CMAF format

SIDX atom being inserted for every MOOF atom increases the muxing overhead.
This behaviour can be disabled for chunked CMAF format by enabling Global SIDX option of mov muxer.

libavformat/dashenc.c

@@ -1065,7 +1065,7 @@ static int dash_init(AVFormatContext *s)
 
         if (c->segment_type == SEGMENT_TYPE_MP4) {
             if (c->streaming)
-                av_dict_set(&opts, "movflags", "frag_every_frame+dash+delay_moov", 0);
+                av_dict_set(&opts, "movflags", "frag_every_frame+dash+delay_moov+global_sidx", 0);
             else
                 av_dict_set(&opts, "movflags", "frag_custom+dash+delay_moov", 0);
         } else {