Solved! Rebuilt System Identical Hardware - Get VLC Tearing

[Vorlon]

I use a Lenovo ThinkCentre desktop (Intel i5, 8 GBytes RAM) for my video server, playing recorded videos using VLC at 2160p with no trouble. My gentoo installation is about 3 years old, but regularly updated to stable (ACCEPT_KEYWORDS=amd64). The profile is the now-obsolete default "/linux/amd64/17.1/desktop".

I've had trouble updating profiles, so instead of updating it to the new profile, I used a second identical ThinkCentre I had to build a duplicate system. I used the same .config file to build the monolithic kernel, the same make.conf file, and loaded the same programs on both machines.

But now I get very bad tearing of videos when being played by VLC.

Things I've checked:

• Same .config for the monolithic kernel
  
• Same make.conf for portage
  
• I'm using the same i915 kernel module in both
  
• I'm loading the same graphic driver (glamoregl) in X on both machines. (they both also load glx & fb)
  
• Both machines report the same hardware using lspci.
  
• Both use Intel Corporation Xeon E3-1200 v3/4th Gen Core Processor Integrated Graphics Controllers
  
• No apparent errors in syslog
  
• No apparent errors in dmesg
  

I've noted these differences between the 2 systems:

• Converted from profile 17.1 to 23.0
  
• The new system boots via UEFI, while the old one booted using the old legacy method.
  
• Pulseaudio is in use on the new system
  
• Good system uses VLC version 3.0.20-r11. The Bad system uses VLC version 3.0.21
  
• VLC USE flags are different (presumably due to the new profile). There are more flags used on the new system. The good system uses "X alsa dbus dvbpsi encode fdk ffmpeg gcrypt gui libsamplerate ncurses run-as-root ssl". The bad system uses "X alsa dbus dvbpsi dvd encode fdk ffmpeg gcrypt gui jpeg libnotify libsamplerate mad ncurses pulseaudio run-as-root ssl truetype udev wayland x264 xml"
  
• Good system used kernel 6.6.47-gentoo. Bad uses 6.6.52-gentoo
  

I would appreciate suggestions of things to check or ways to improve video playback performance.

TIA!
_________________
Casey Bralla
Chief Nerd in Residence
The NerdWorld Organisation

[Ralphred]

[Vorlon]

I found the solution... not what I had expected.

I had checked the Xorg configuration and the VLC settings as Ralphred had suggested, but they were identical. I also tried a third identical computer where I had cloned the disk from the second badly behaving computer. It had bad tearing in VLC also.

The problem was the "scale" factor I had used in the xfce4 Display settings on the new (bad) computer.

My monitor is a very large 2160p in my living room. Unfortunately, at 2160p all the text and icons too small to see easily from my sofa. So on the new (bad) system, I had set the Display scale factor to 0.5, which made everything MUCH easier to read. On the old (good) system, I had left the scale at 1.0, and just bumped up the default font sizes. This helped, but still left it hard to see small icons on various applications.

When I set the Display scale back to 1, and then increased the font sizes, all the tearing disappeared on the new (formerly bad) system.

So the lesson is: Don't use scaling if you want to play lots of videos in VLC.
_________________
Casey Bralla
Chief Nerd in Residence
The NerdWorld Organisation