Bug 199378 – [GStreamer] Video quality with gstreamer-vaapi is bad

• Component: Media
• Status: RESOLVED WORKSFORME

Using GNOME Web 3.32.3 (WebKitGTK+ 2.24.2)

The Video quality is bad. Attached are screenshots from Epiphany using WebKitGTK+ and Firefox for comparison.

Test site: https://www.w3schools.com/html/tryit.asp?filename=tryhtml5_video

open the direct video url to make sure the video isn't scaled: https://www.w3schools.com/html/mov_bbb.mp4



Redirected from https://gitlab.gnome.org/GNOME/epiphany/issues/834

Created attachment 373260 [details]
Screenshot Epiphany

Created attachment 373261 [details]
Screenshot Firefox

[Michael Catanzaro]

FWIW: I see the good result (like your Firefox image) in Ephy Tech Preview.

I currently can't build a newer version. There is nothing wrong with the resolution.

It is related with vaapi. The artifacts aren't as bad on Intel hardware (initial screenshot is from AMD), but the colours are wrong. Uninstalling gstreamer-vaapi "solves" the issue, however the colours are still oversaturated in comparison to Chromium and Firefox, which look identical to my eye.

[Alicia Boya García]

I would say the colors are the same, the problem is the Epiphany one is being painted with a half pixels offset, resulting in blur.

[Alicia Boya García]

(at least in the attached screenshots)

Yes, I haven't attached screenshots with Intel hardware yet. I can post some later, but I'm not sure this would be no separate issue.

[Michael Catanzaro]

(In reply to grmat from comment #5)
> I currently can't build a newer version. There is nothing wrong with the
> resolution.

Sorry, that was a spammer pretending to leave a relevant comment.

[Michael Catanzaro]

So either we fix bug #197752 and mark this as a dup, or we take responsibility for fixing vaapi bugs like this....

Sorry for the dup. I haven't searched for vaapi before filing.

I can't contribute technically and I'm not deep into this topic. Just from a user POV, it would be a shame if vaapi was blacklisted. I actually put hope in smaller webkit based browsers like epiphany because the major browser vendors fail to support hardware accel video on Linux for years.

Can you say that it's the driver's fault? Then I'll report the quality issues to AMD as well.

I also don't know how much Webkit can do or whether there is room for configuration. What I can say is that I'm using VAAPI with mpv all the time and it doesn't show any quality issues at all.

I actually just tested the above linked video with mpv+vaapi on the AMD hardware and the frame looks identical to the Firefox one.

Created attachment 373918 [details]
Screenshot Intel

Using gstreamer-vaapi in Epiphany on Intel, the video looks oversaturated

Created attachment 373919 [details]
mpv screenshot

mpv, which also uses VA-API btw, for reference.

[Philippe Normand]

Is this still an issue?

BTW, PSA: in 2.38 gstreamer-vaapi decoders will not be used, unless the WEBKIT_GST_ENABLE_LEGACY_VAAPI env var is set to 1. The new stateless va decoders will be used, supposing their rank is high enough, which can be ensured by setting this env var: GST_PLUGIN_FEATURE_RANK=vah264dec:MAX

[Philippe Normand]

Please give this a try with the new decoder has mentioned in previous comment. Feel free to re-open if the issue is still happening.