Something broken with Opus in MPEG-TS support

I came across something funky with Opus in MPEG-TS that needs further investigation.

Using git master:

gst-launch-1.0 audiotestsrc num-buffers=1000 ! audio/x-raw,channels=2 ! opusenc bitrate=64000 ! mpegtsmux name=mux ! filesink location=~/test-master.ts

produces a file (test-master.ts) that plays back OK in both 1.16 and git master, but using 1.16 (test-1.16.ts) to generate the file produces a file that only 1.16 can play. git master thinks the file contains AC-4 audio.

VLC can play both files fine.

WARNING No decoder available for type 'audio/x-ac4'.
WARNING debug information: ../subprojects/gst-plugins-base/gst/playback/gsturidecodebin.c(957): unknown_type_cb (): /GstPlayBin:playbin/GstURIDecodeBin:uridecodebin0
ERROR Your GStreamer installation is missing a plug-in. for file:///home/jan/test-1.16.ts
ERROR debug information: ../subprojects/gst-plugins-base/gst/playback/gsturidecodebin.c(1024): no_more_pads_full (): /GstPlayBin:playbin/GstURIDecodeBin:uridecodebin0:
no suitable plugins found:
../subprojects/gst-plugins-base/gst/playback/gstdecodebin2.c(4717): gst_decode_bin_expose (): /GstPlayBin:playbin/GstURIDecodeBin:uridecodebin0/GstDecodeBin:decodebin0:
no suitable plugins found:
Missing decoder: audio/x-ac4 (audio/x-ac4)

Reached end of play list.