At Sun, 8 Apr 2007 20:35:32 -0400, Lee Revell wrote:
On 4/7/07, Simon Lewis simon.lewis@mnet-online.de wrote:
Dear Alsa developers
Audacity seems to work perfectly with AOSS and Jack but not directly with ALSA on some linux PCs. Trying to use ALSA directly leads to severe distortion due to lack of sync with Alsa. (I hope that is the correct terminology.)
I received this reply from the Audacity developers, what tools are available from ALSA to investigate this problem? How can I determine what the real "Alsa configuration" is that portaudio has used setting up communication with Alsa.
Please try to narrow it down some. What hardware/kernel/distro versions work OK and which don't? Especially important is the motherboard chipset, ALSA version and exact make/model of soundcard.
My guess is that different soundcards default to different period/buffer config values, and that Audacity wrongly assumes the buffer/period size it gets from ALSA by default is sane on all hardware.
Yes, and note that one of the most complicated things is the use of dmix/dsnoop plugin. Many devices are set up to use dmix/dsnoop as default with ALSA, so when you open the PCM via "default" name, the dmix/dsnoop will be invoked automatically. When dmix plugin is used, many parameters are restricted via the plugin setting rather than the hardware constraints.
I believe the recent dmix/dsnoop code is stable enough, but it's worth to try once "hw" PCM instead of "default" PCM to reduce the possible problems around plugins.
Takashi