Adding `! vah264enc ! vah264dec` to pipeline introduces weird artifacts

I’ve only recently begun learning to use gstreamer. A few days ago I was able to get the following two pipelines connected over the network:

gst-launch-1.0 -v videotestsrc ! "video/x-raw, width=(int)1920, height=(int)1080, framerate=(fraction)30/1" ! x264enc ! h264parse ! rtph264pay ! udpsink host= port=5002


gst-launch-1.0 -v udpsrc port=5002 caps="application/x-rtp" ! rtph264depay ! parsebin ! vah264dec ! videoconvert ! videoscale ! xvimagesink

(I was using these to prototype the concept for an idea i want to apply in my own application)

Yesterday I upgraded my gstreamer Arch packages from 1.22.7 to 1.22.8, after which I began seeing scan line like artifacts (not sure if that’s the right terminology) in the output when i include ! vah264enc ! vah64dec as in the following simplified example:

gst-launch-1.0 -v videotestsrc ! "video/x-raw, width=(int)1920, height=(int)1080, framerate=(fraction)60/1" ! vah264enc ! vah264dec ! queue ! xvimagesink

(removing the ! vah264enc ! vah264dec from this removes the scan line artifacts).

Here is a screenshot demonstrating the scan line artifacts I am talking about:

I’m wondering if anyone can point me in the direction of a troubleshooting approach to figure out what’s going on? For what it’s worth I’ve already tried downgrading the gstreamer packages back to the previous 1.22.7-1 Arch package and the problem seems to persist.

I also filed a bug report on the git repo with slightly different details from what I’ve mentioned here: vah264enc/vah264dec after recent upgrade to 1.22.8 from 1.22.7 (#3195) · Issues · GStreamer / gstreamer · GitLab

Okay it looks like the problem isn’t in any of the gstreamer packages but in one of the mesa packages that were upgraded alongside the gstreamer packages on my system: mesa lib32-mesa libva-mesa-driver mesa-vdpau

I was able to solve the issue on my system by adding these packages to the IgnorePkg list in /etc/pacman.conf and manually downgrade them to the previous version in my package cache, eg

pacman -U /var/cache/pacman/pkg/lib32-mesa-1:23.2.1-2-x86_64.pkg.tar.zst /var/cache/pacman/pkg/lib32-vulkan-radeon-1:23.2.1-2-x86_64.pkg.tar.zst /var/cache/pacman/pkg/libva-mesa-driver-1:23.2.1-2-x86_64.pkg.tar.zst /var/cache/pacman/pkg/mesa-1:23.2.1-2-x86_64.pkg.tar.zst /var/cache/pacman/pkg/mesa-vdpau-1:23.2.1-2-x86_64.pkg.tar.zst /var/cache/pacman/pkg/vulkan-radeon-1:23.2.1-2-x86_64.pkg.tar.zst

After doing this the weird visual artifact I describe here no longer shows up.

According to someone on gitlab there is a set of fixes targeting the gstreamer 1.22 branch that may address the issue: Backport of "va: fixes for Mesa driver" into 1.22 (!5778) · Merge requests · GStreamer / gstreamer · GitLab