In gsturidecodebin.c, adaptive_media is judaged by following type:


/* media types that use adaptive streaming */
static const gchar *adaptive_media[] = {
  "application/x-hls", "application/x-smoothstreaming-manifest",
  "application/dash+xml", NULL
};

But in gsttypefindfunctions.c
Smooth Streaming is as below:

static GstStaticCaps mss_manifest_caps =
GST_STATIC_CAPS ("application/vnd.ms-sstr+xml");

If we compare the flow betweeen DASH & MSS, from the graph dump we could see 
DASH does NOT have Queue2 but MMS has.
It is because the following logic:

  if (decoder->is_adaptive) {
    src_elem = typefind;  ==> DASH
  } else {
    if (do_download) {
      elem_name = "downloadbuffer";
    } else {
      elem_name = "queue2";  ==> MSS
    }
  ... 

However, MSS indeed is a kind of "adaptive streaming" source.

It is because the media type mis-match.

We could fix it either by:

/* media types that use adaptive streaming */
static const gchar *adaptive_media[] = {
  "application/x-hls", /*"application/x-smoothstreaming-manifest",*/
  "application/dash+xml", "application/vnd.ms-sstr+xml", NULL
}; 
or replace "application/vnd.ms-sstr+xml" by "application/x-smoothstreaming-manifest".

It potentially mis-judge MSS as a "NON-adaptive-streaming" type.