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FC6 Sound Support on the HP Pavilion Notebook

[Updated 6/29/07 for latest FC6 with planetccrma-* installed.]

Sound support is usable, but not smooth. The mute button and volume level slider are not supported at all, so a tool like alsamixer is necessary to set volumes and toggle mutes.

Plugging something into the headphone jack once (but not always) resulted in the master gain being muted, and nothing seems to unmute it automatically, so I had to unmute the master gain in alsamixer. [This seems to be working better as of 9/4/07.] (To do this, type `m' with the far-left slider selected to change ``MM'' to '00' in the mute indicator). Also, the default system speaker volume was initially zero (use the up-arrow key to raise it).

The ``play'' command-line function (by sox) works fine, as long as the jack audio server is not running. The same goes for the ALSA aplay command.

Audacity for FC6 works as long as I manually set the sampling rate (to 48000 Hz) and word format (to 16-bit) before playing--otherwise it hangs.

Because I had done a yum install jack-audio-server prior to installing Planet CCRMA, I had the problem that the jack audio server would not start unless root launched it (``cannot use real-time scheduling (FIFO at priority 10) [for thread nnn, from thread nnn] (1: Operation not permitted); cannot create engine''). Subsequently, audacity could not connect to jack (``Error while opening sound device. ...'') unless it too was run by root. As a normal user, I could only run audacity in stand-alone mode. Similarly, the sndplay command (which is jack-aware) only worked for root if the jack server was running, and it worked for normal users otherwise.

According to Fernando (on the Planet CCRMA mailing list): ``You need to edit a configuration to allow non-root users to have access to realtime scheduling and memory locking (that was "automatically" done in Planet CCRMA with a patched version of the pam package). In /etc/security/limits.conf add:

--- cut here ---
# or (default) allow everyone access
*               -       rtprio          99
*               -       nice            -10
*               -       memlock         4000000
--- cut here ---
You'll need to logout and login again for that to take effect.'' If you obtain the jack audio server via the Planet CCRMA procedure, this should be taken care of automatically for you.

On my HP notebook, using default settings, the jack audio server obtained chronic sound-out underruns (``xruns''). These are clearly audible as periodic gaps in the sound. Eventually I hit upon changing ``Periods/Buffer'' from the default 2 to 3. (Setting it to 4 resulted in failure of jackd to start.) Prior to that, I had set Frames/Period to 4096 (the maximum sound-buffer size). Fiddling with Priority did not seem to affect anything. I had also checked ``Force 16bit'' which seems to now be required (unchecking it also results in a failure of jack to start).

I assume my sound device is a standard AC-97 CODEC, which means the hardware sampling rate is undoubtedly 48000 Hz. I find I can set the jack server sampling rate to 44100 as well, indicating that there is plenty of bandwidth for on-the-fly sampling-rate conversion.

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``My Computers'', by Julius O. Smith III, Web document.
Copyright © 2015-11-29 by Julius O. Smith III
Center for Computer Research in Music and Acoustics (CCRMA),   Stanford University