msdk: Got NULL mfx surface in "intervideosink + intervideosrc" pipeline with msdkvpp element

When running the GStreamer command line:

gst-launch-1.0 -v videotestsrc ! msdkvpp ! video/x-raw, width=1280, height=800, format=BGRA ! \
intervideosink channel=frontvideosink sync=true async=false render-delay=5000000 max-lateness=5000000 \
intervideosrc channel=frontvideosink ! msdkvpp ! video/x-raw, width=640, height=480, format=NV12 ! \
msdkh264enc name=main_enc bitrate=1500 rate-control=2 ! video/x-h264, stream-format=byte-stream ! \
queue ! h264parse ! msdkh264dec ! vaapisink sync=false

I got the error:

0:00:00.092319589  5840 0x559b3f5369e0 ERROR                msdkvpp gstmsdkvpp.c:861:gst_msdkvpp_transform:<msdkvpp1> mfx surface is NULL for the current input buffer

But I can see video playback without any error, by replacing msdkvpp with mfxvpp:

gst-launch-1.0 -v videotestsrc ! mfxvpp ! video/x-raw, width=1280, height=800, format=BGRA ! \
intervideosink channel=frontvideosink sync=true async=false render-delay=5000000 max-lateness=5000000 \
intervideosrc channel=frontvideosink ! mfxvpp ! video/x-raw, width=640, height=480, format=NV12 ! \
msdkh264enc name=main_enc bitrate=1500 rate-control=2 ! video/x-h264, stream-format=byte-stream ! \
queue ! h264parse ! msdkh264dec ! vaapisink sync=false

or by replacing the 1st msdkvpp before intervideosink, with vaapipostproc:

gst-launch-1.0 -v videotestsrc ! vaapipostproc ! video/x-raw, width=1280, height=800, format=BGRA ! \
intervideosink channel=frontvideosink sync=true async=false render-delay=5000000 max-lateness=5000000 \
intervideosrc channel=frontvideosink ! msdkvpp ! video/x-raw, width=640, height=480, format=NV12 ! \
msdkh264enc name=main_enc bitrate=1500 rate-control=2 ! video/x-h264, stream-format=byte-stream ! \
queue ! h264parse ! msdkh264dec ! vaapisink sync=false

Issue reproducing configuration:

• Platform: Intel Tiger Lake (11th Gen Intel(R) Core(TM) i5-1135G7 @ 2.40GHz)
• Software Configuration:
  • Ubuntu 18.04
  • Linux kernel 5.8.1-050801-generic
  • Latest master branch of "libva, gmmlib, media-driver (iHD), gstreamer, gst-plugins-base, gst-plugins-good, gst-plugins-ugly, MediaSDK, gst-plugins-bad, gstreamer-media-SDK, gstreamer-vaapi"