On Wed, 17.02.10 11:44, Raymond Yau (superquad.vortex2@gmail.com) wrote:
WHAT YOU NEED?
a) A sound card where input and output are synchronous b) A feedback cable that allows you to feed sound card outputhow do I know my sound card support synchronous playback and capture ?
We had a discussion about that on alsa-devel a month back or so. The conclusion was basically that software may assume that playback and capturing on the same card is clocked the same way and that is all this tool needs.
do you program able to find out whether the sound card support synchronous playback and capture ?
No.
do your result still valid if the sound card does not support synchronous playback and capture ?
It's fine if there is a constant phase shift between what you play back and record. What matters is that the clock of playback and clock of capture have the same speed. The tool will sum up a recorded sample window a couple of times to reduce the noise level below some threshold, and for that to work we need to make sure that our sine wave isn't shifted each time we sum it up.
do the result different if I use analog loop back of the ac97 codec instead of a loop back cable ?
Presumably.
Lennart