IMX8MM Hantro VP9 decode failure

[Tim Harvey]

Greetings,

I'm testing the VP9 hantro kernel support on an IMX8MM with the following:
- imx8mm-venice-gw73xx-0x board with a 800x480 MIPI DSI display
- v5.16-rc3 kernel with:
  - [PATCH v7 00/11] VP9 codec V4L2 control interface
  - IMX8MM DSI support added (some old patchsets)
  - GStreamer 1.19.3+

 with vp9 backported, hantro support added, and imx8mm display support added
- gstreamer 1.19.3 (git sha b5c07e11ca)

I see the v4l2 stateless decoder:
[gst-main] root at focal-venice:~/gstreamer/build# gst-inspect-1.0
v4l2codecs | grep v4l2slvp9dec
  v4l2slvp9dec: V4L2 Stateless VP9 Video Decoder

I'm generating a test stream on an x86 with GStreamer 1.19.3 (git sha
05458f05e0):
gst-launch-1.0 -v videotestsrc ! video/x-raw,width=800,height=480 !
vp9enc ! rtpvp9pay ! udpsink host=172.24.33.15 port=9001

I'm decoding on imx8mm with:
gst-launch-1.0 udpsrc port=9001 caps =
'application/x-rtp,media=(string)video, clock-rate=(int)90000,
encoding-name=(string)VP9,payload=(int)96, ssrc=(uint)2246741422,
timestamp-offset=(uint)3441735424,
seqnum-offset=(uint)30250,a-framerate=(string)30' ! rtpvp9depay !
v4l2slvp9dec ! fakesink
^^^ this fails with no-negotiated

Things seem to be very bleeding edge with VP9 so I'm not sure if I
need very specific gstreamer versions here or not.

Best regards,

Tim