Le 29/01/2013 22:02, Ralf Mardorf a écrit :
On Tue, 29 Jan 2013 21:58:41 +0100, Rob Owens <rowens@ptd.net> wrote:On Tue, Jan 29, 2013 at 03:02:01PM +0100, dAgeCKo wrote:Hello, I am currently facing a strange problem with ALSA and Jack. I play electric guitar sometimes and I use my computer as a medium to output the sound. For this, I use jack, with alsa as the driver. Half of the time, everything is just fine, the audio output of my guitar is just what it should be. However, sometimes, the sound is completely low, distorted and with a lot of cracklings and looks to have been produced by an awful and very old synthesizer.Could it be that you are experiencing xruns? (This is jackd's term for a buffer over- or under-run in your sound card). xruns typically make a popping or crackling sound. Qjackctl should show xruns in red in its main interface.If so, CPU frequency scaling comes to mind. If it's not set to performance, it could cause xruns.
That sounds interesting and could make sense regarding my configuration (cpu scaling set to ondemand). I would never believe cpu scaling could provoke this (several RT programs run on almost every linux).
So I will have a look at this tomorrow and let you know.
Btw. what are your jack settings?
The settings are quite common, with some minor changes for a better latency: driver: alsa RT with default priority samples/period: 128 sampling freq: 96000 period/buffer: 3 max numb of ports: 128 count-down: 500 dither: none audio: duplex input device: hw:0 output device: hw:0 late start: 2 seconds for a final calculated latency of 4ms