Enable Hardware acceleration on Linux

[Revival8697]

Instructions to enable Hardware acceleration on Arch Linux

Also see #961. To be fixed by #4532.

1. Install and verify that VA-API is working.

2. Install the nightly build of FreeTube. The nightly build has up to date Electron therefore easier to work with.

   You can use stable build but it may be harder to find the working flags.

3. Append the necessary flags:

• Copy FreeTube desktop file to user directory:

cp /usr/share/applications/freetube.desktop ~/.local/share/applications/freetube.desktop

• Check the Arch Wiki for the newest information on which flags are needed.

• Test the flags by launching FreeTube with a terminal: freetube --flag1 --flag2 and play a test video at 1080p60.

• For Intel GPU, use intel_gpu_top and see if the Video engine is being used. For others, monitor the CPU with htop and GPU with nvtop, you should see less CPU usage and more GPU usage when Hardware acceleration is working. You may have to experiment multiple times before finding the correct flags for your GPU.

  Note: As of writing, only --enable-features=VaapiVideoDecodeLinuxGL is needed (for my Intel 10th Gen GPU).

• Open ~/.local/share/applications/freetube.desktop with a text editor and append the flags to the Exec=freetube %U line. Remember to save the file.

  For example, mine looks like this: Exec=freetube %U --enable-features=VaapiVideoDecodeLinuxGL.

[Revival8697]

#4532 (merged) will fix this without end-user interactions.

Test builds are available at here.

[absidue]

It's not stale, we just haven't reviewed it yet, 6 days is nothing, especially for a pull request that you'll need an actual linux machine to review it, as i doubt that trying to test hardware acceleration in a vm is going to go well.