QtMultimedia (qmlvideo) does not play rtsp stream (No decoder available for type application/x-rtp)

0:00:02.666240768 14268 0x7f3858006b70 WARN               decodebin gstdecodebin2.c:4592:gst_decode_bin_expose:<decodebin2> error: no suitable plugins found:
Missing decoder: application/x-rtp (application/x-rtp, media=(string)application, payload=(int)100, clock-rate=(int)90000, encoding-name=(string)STREAM-ASSIST-FRAME, a-packetization-supported=(string)DH, a-rtppayload-supported=(string)DH, a-recvonly=(string)"", ssrc=(uint)1619523952, clock-base=(uint)63856, seqnum-base=(uint)63856, npt-start=(guint64)0, play-speed=(double)1, play-scale=(double)1)

Starting /home/debian/Qt/Examples/Qt-5.9.3/multimedia/video/build-qmlvideo-Desktop_Qt_5_9_3_GCC_64bit-Release/qmlvideo...
0:00:02.298414542 14268 0x55d41d484a00 FIXME                    bin gstbin.c:4350:gst_bin_query: implement duration caching in GstBin again
0:00:02.300814450 14268 0x55d41d484a00 FIXME                    bin gstbin.c:4350:gst_bin_query: implement duration caching in GstBin again
0:00:02.326638039 14268 0x55d41d484a00 FIXME                    bin gstbin.c:4350:gst_bin_query: implement duration caching in GstBin again
0:00:02.326691878 14268 0x55d41d484a00 FIXME                    bin gstbin.c:4350:gst_bin_query: implement duration caching in GstBin again
0:00:02.377707216 14268 0x55d41d484a00 FIXME                    bin gstbin.c:4350:gst_bin_query: implement duration caching in GstBin again
0:00:02.379078141 14268 0x55d41d484a00 FIXME                    bin gstbin.c:4350:gst_bin_query: implement duration caching in GstBin again
0:00:02.480994371 14268 0x55d41d484a00 FIXME                    bin gstbin.c:4350:gst_bin_query: implement duration caching in GstBin again
0:00:02.481035983 14268 0x55d41d484a00 FIXME                    bin gstbin.c:4350:gst_bin_query: implement duration caching in GstBin again
0:00:02.543182871 14268 0x7f387404e050 FIXME                default gstutils.c:3826:gst_pad_create_stream_id_internal:<fakesrc0:src> Creating random stream-id, consider implementing a deterministic way of creating a stream-id
0:00:02.544957259 14268 0x7f387404e0f0 FIXME                default gstutils.c:3826:gst_pad_create_stream_id_internal:<fakesrc1:src> Creating random stream-id, consider implementing a deterministic way of creating a stream-id
0:00:02.545341838 14268 0x7f387404e0a0 FIXME                default gstutils.c:3826:gst_pad_create_stream_id_internal:<fakesrc2:src> Creating random stream-id, consider implementing a deterministic way of creating a stream-id
0:00:02.666103144 14268 0x7f3858006b70 WARN            uridecodebin gsturidecodebin.c:938:unknown_type_cb:<uridecodebin0> warning: No decoder available for type 'application/x-rtp, media=(string)application, payload=(int)100, clock-rate=(int)90000, encoding-name=(string)STREAM-ASSIST-FRAME, a-packetization-supported=(string)DH, a-rtppayload-supported=(string)DH, a-recvonly=(string)"", ssrc=(uint)1619523952, clock-base=(uint)63856, seqnum-base=(uint)63856, npt-start=(guint64)0, play-speed=(double)1, play-scale=(double)1'.
0:00:02.666207204 14268 0x7f3858006b70 WARN                 default descriptions.c:1222:gst_pb_utils_get_codec_description: No description available for media type: application/x-rtp
0:00:02.666240768 14268 0x7f3858006b70 WARN               decodebin gstdecodebin2.c:4592:gst_decode_bin_expose:<decodebin2> error: no suitable plugins found:
Missing decoder: application/x-rtp (application/x-rtp, media=(string)application, payload=(int)100, clock-rate=(int)90000, encoding-name=(string)STREAM-ASSIST-FRAME, a-packetization-supported=(string)DH, a-rtppayload-supported=(string)DH, a-recvonly=(string)"", ssrc=(uint)1619523952, clock-base=(uint)63856, seqnum-base=(uint)63856, npt-start=(guint64)0, play-speed=(double)1, play-scale=(double)1)

0:00:02.667262701 14268 0x7f387404e400 WARN                 basesrc gstbasesrc.c:2950:gst_base_src_loop:<udpsrc6> error: Internal data stream error.
0:00:02.667290827 14268 0x7f387404e400 WARN                 basesrc gstbasesrc.c:2950:gst_base_src_loop:<udpsrc6> error: streaming stopped, reason not-linked (-1)
qml: [qmlvideo] VideoItem.onError error 2 errorString Cannot play stream of type: <unknown>
qml: [qmlvideo] Content.onFatalError
0:00:02.670339878 14268 0x7f3844017e30 WARN                GST_PADS gstpad.c:4106:gst_pad_peer_query:<decodebin0:src_0> could not send sticky events
0:00:02.670431828 14268 0x7f3844017e30 WARN                GST_PADS gstpad.c:4106:gst_pad_peer_query:<decodebin0:src_0> could not send sticky events
0:00:02.803801281 14268 0x55d41dffaad0 WARN                 rtspsrc gstrtspsrc.c:5505:gst_rtspsrc_try_send:<source> send interrupted
0:00:02.803826567 14268 0x55d41dffaad0 WARN                 rtspsrc gstrtspsrc.c:7588:gst_rtspsrc_pause:<source> PAUSE interrupted
0:00:02.807714944 14268 0x55d41dffaad0 WARN                 rtspsrc gstrtspsrc.c:5505:gst_rtspsrc_try_send:<source> send interrupted
0:00:02.807730883 14268 0x55d41dffaad0 WARN                 rtspsrc gstrtspsrc.c:7043:gst_rtspsrc_close:<source> TEARDOWN interrupted
Warning: "No decoder available for type 'application/x-rtp, media=(string)application, payload=(int)100, clock-rate=(int)90000, encoding-name=(string)STREAM-ASSIST-FRAME, a-packetization-supported=(string)DH, a-rtppayload-supported=(string)DH, a-recvonly=(string)\"\", ssrc=(uint)1619523952, clock-base=(uint)63856, seqnum-base=(uint)63856, npt-start=(guint64)0, play-speed=(double)1, play-scale=(double)1'."
0:00:02.817327462 14268 0x55d41d484a00 FIXME                    bin gstbin.c:4350:gst_bin_query: implement duration caching in GstBin again
0:00:02.817364648 14268 0x55d41d484a00 FIXME                    bin gstbin.c:4350:gst_bin_query: implement duration caching in GstBin again
0:00:03.218046762 14268 0x55d41d484a00 FIXME                    bin gstbin.c:4350:gst_bin_query: implement duration caching in GstBin again
0:00:03.218173987 14268 0x55d41d484a00 FIXME                    bin gstbin.c:4350:gst_bin_query: implement duration caching in GstBin again
/home/debian/Qt/Examples/Qt-5.9.3/multimedia/video/build-qmlvideo-Desktop_Qt_5_9_3_GCC_64bit-Release/qmlvideo exited with code 0

$ env PHONON_BACKEND=phonon_gstreamer PHONON_BACKEND_DEBUG=2 PHONON_DEBUG=2 dragon 
Stopped state
updated actions
updated menus
set titles 
seekable changed to  false
Opening QUrl("rtsp://admin@192.168.1.108:80/cam/realmonitor?channel=1&subtype=0&proto=Private3")
detected mimetype:  "application/octet-stream"
QPainter::begin: Paint device returned engine == 0, type: 2
Initial offset is  0
using index:  -1  returned desc has index:  -1
using index:  0  returned desc has index:  -1
chapters:  0  titles:  0
going from  "Loading"  to  "Stopped"
Stopped state
updated actions
updated menus
set titles 
chapters:  0  titles:  0
going from  "Stopped"  to  "Paused"
Paused state
updated actions
updated menus
set titles 
PHONON-GST [WARNING] "Warning: gsturidecodebin.c(938): unknown_type_cb (): /GstPlayBin:playbin0/GstURIDecodeBin:uridecodebin0\nMessage:No decoder available for type 'application/x-rtp, media=(string)application, payload=(int)100, clock-rate=(int)90000, encoding-name=(string)STREAM-ASSIST-FRAME, a-packetization-supported=(string)DH, a-rtppayload-supported=(string)DH, a-recvonly=(string)\"\", ssrc=(uint)393883596, clock-base=(uint)12236, seqnum-base=(uint)12236, npt-start=(guint64)0, play-speed=(double)1, play-scale=(double)1'."
hasVideo changed true
Paused state
updated actions
updated menus
set titles 
()
()
()
metaDataChanged
Disc ID: ""
set titles 
()
()
()
 update recent files list 
()
()
()
metaDataChanged
Disc ID: ""
set titles 
seekable changed to  false
chapters:  0  titles:  0
going from  "Paused"  to  "Playing"
Updating channels, subtitle count: 0
adjusting size to video resolution
Playing state
updated actions
updated menus
set titles 
stop cursorTimer
trying to fetch subtitle information
fetched subtitle information

$ fgrep rtsp /proc/$(pgrep dragon)/maps
7f6297a3a000-7f6297a57000 r-xp 00000000 08:01 793567                     /usr/lib/x86_64-linux-gnu/libgstrtsp-1.0.so.0.1004.0
7f6297a57000-7f6297c56000 ---p 0001d000 08:01 793567                     /usr/lib/x86_64-linux-gnu/libgstrtsp-1.0.so.0.1004.0
7f6297c56000-7f6297c59000 r--p 0001c000 08:01 793567                     /usr/lib/x86_64-linux-gnu/libgstrtsp-1.0.so.0.1004.0
7f6297c59000-7f6297c5a000 rw-p 0001f000 08:01 793567                     /usr/lib/x86_64-linux-gnu/libgstrtsp-1.0.so.0.1004.0
7f6297e7a000-7f6297e9f000 r-xp 00000000 08:01 139315                     /usr/lib/x86_64-linux-gnu/gstreamer-1.0/libgstrtsp.so
7f6297e9f000-7f629809f000 ---p 00025000 08:01 139315                     /usr/lib/x86_64-linux-gnu/gstreamer-1.0/libgstrtsp.so
7f629809f000-7f62980a0000 r--p 00025000 08:01 139315                     /usr/lib/x86_64-linux-gnu/gstreamer-1.0/libgstrtsp.so
7f62980a0000-7f62980a1000 rw-p 00026000 08:01 139315                     /usr/lib/x86_64-linux-gnu/gstreamer-1.0/libgstrtsp.so