Sonntag, 8. September 2013

[Steam][SDL][OpenAL] Stuttering sound in many Linux games

Hello folks.
On my Linux system (up-to-date Arch Linux) I was having trouble with several open-al based games, namely Psyschonauts, Super Hexagon and FTL/Faster Than Light. All games were purchased via Steam. The problem was, that the games' sounds came out somehow garbled - stuttering to be more precise. All I could do was restarting the game once or twice and hope that it would finally do as intended. As there are several components involved and common to the stuttering sound (SDL, OpenAL, Steam, Pulse Audio, Linux), it was not easy for me to put the problem into words google could understand.

After doing a lot of research with no results of which none of them solved my problems, I finally stumbled about a small, german  forum post, that seemed somehow to be connected to this issue. It also mentioned high cpu load when these problems occur, which I could confirm espacially while playing FTL. The post was suggesting that it might help to go into Mixer/ Pavu Control, take the particular audio stream of the game (for steam games it is usually a steam-connected strem), and turn it down a little - from 100% to let's say 90%. And voilà: After following this advice I seem to have no troubles left with those games.
If you don't have a program calles "Pavu control" or Pulse audio Mixer yet, it is almost certain that you will find it in your distribution's repository.
And that's it!

But wait - what happened? As the mentioned post suggests, it is a problem of the sound overmodulating. I guess, there is an (artificial) limit set to the physical outgoing sound volume, that causes sounds which are too loud to be filtered. Since this is probably an expensive operation, intercepting the audio stream, filter it and continue to play it again, this will presumably cause the high cpu usage noticed before. I don't know why, but openAL seems to cause a lot of those too-high sounds to be generated (at least the version used by steam).
Now, by setting the limit of the virtual stream lower than before, this problem gets solved.

Happy playing!

1 Kommentar:

  1. I had a similar problem, adjusting the volumes had no effect.
    Switchting from surround to stereo (like mentioned in: http://steamcommunity.com/app/221410/discussions/0/864959088185862027/) did it

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