Subject: Re: [ecasound] full-duplex sync
From: Kai Vehmanen (kaiv_AT_wakkanet.fi)
Date: Fri Oct 12 2001 - 18:16:06 EEST
> Things that may be "non-noticeable" to you are noticeable to us.
> What we care about is !exact! sync between input and output.
Ecasound can't guarantee sample-level sync. Achieving
it requires that capture and playback are started
_exactly_ at the same time. And this can be only
done with hw-level support. Without limiting
ecasound to some specific sync-API, this is not possible.
So ecasound uses a different approach. It starts
devices independently, but records the exact time
of triggering. Using this information, ecasound
can fix possible sync-offsets when writing to
output files. This method works and requires very
little support from the driver-level.
I suggest you take a look at ardour (ardour.sourceforge.net).
Ardour has always been ALSA-only and thus it can
more easily take advantage of ALSA's features. Hw-sync
support was added to the new ALSA 0.9/0.6 version, but
I don't know if Ardour uses it yet. But it's worth
checking.
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