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Bad quality decoding

Posted: 10 Mar 2022 23:45
by Houdini_Cat
I am using VLC 3.0.16 under XUbuntu 21.10 and the decoded output has a very bad quality.

First I have recorded a video with OBS with some text inside of the video and then I want to see the result/quality and it was very bad.
I increased the bitrate and the quality, but it was useless ... till I opened it with MPlayer and Parole, there the quality was very good.

I compared the pictures (decoding-result) which I get from VLC-Player and Parole-Player from the same video-file.

Parole-Player:
Image

VLC-Player:
Image

The control of the VLC-Player is much better, but the quality is very bad. Why?

Re: Bad quality decoding

Posted: 11 Mar 2022 16:27
by Rémi Denis-Courmont
Probably VLC is configured to use a different scaling method that is poorly implemented (potentially in the GPU drivers).

Re: Bad quality decoding

Posted: 11 Mar 2022 16:58
by elitedata
turn off de-interlacing, its likely set to "automatic" or its turned on.
Image

Re: Bad quality decoding

Posted: 11 Mar 2022 22:09
by Houdini_Cat
Probably VLC is configured to use a different scaling method that is poorly implemented (potentially in the GPU drivers).
You are right, on my Intel i7 I can see this without any problem with VLC.
What can I do or how can I tell somebody who is working on the GPU-driver (AMD Ryzen 7 5700G) that there is a problem?
For my graphic I use the driver which is integrated into the Linux Kernel.

Re: Bad quality decoding

Posted: 11 Mar 2022 22:15
by Houdini_Cat
turn off de-interlacing, its likely set to "automatic" or its turned on.
Image
I can see a difference if the resolution must be scaled down on my Laptop-screen, this looks very similar.
In my case it have something to do with the GPU-driver, because on my Intel Laptop it looks fine if de-interlacing is off. On my AMD Desktop PC, there was no difference between Auto, off and on, because no the source was 1080p and the screen is 1080p too, so no scaling of the image is needed.

Re: Bad quality decoding

Posted: 12 Mar 2022 01:24
by elitedata
its possible the driver is forcing deinterlacing regardless of resolution, the sample image appears to be deinterlaced.
is there AMD "desktop" software to configure such settings ?

Re: Bad quality decoding

Posted: 12 Mar 2022 22:25
by Houdini_Cat
its possible the driver is forcing deinterlacing regardless of resolution, the sample image appears to be deinterlaced.
Yes, this is possible.

Image
If you see the letters, then it looks like there are some shadows behind the letters, with e position only one or two pixel higher.

I don't know who I should tell that there is a bug in the driver. The Linux-Kernel Team? Ubuntu bug report?
https://bugs.launchpad.net/ubuntu
They always ask which package is affected. :-/
is there AMD "desktop" software to configure such settings ?
I use XUbuntu and there are no additional (proprietary) driver available and I do not want to use them, because of bad experience.
The driver in the Linux-Kernel are normally better.

Re: Bad quality decoding

Posted: 13 Mar 2022 08:48
by Rémi Denis-Courmont
If you have the latest version of the drivers, then that's probably the Mesa project.