Re: [ecasound] cloops, synchronization

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Subject: Re: [ecasound] cloops, synchronization
From: Kai Vehmanen (
Date: Tue Apr 04 2000 - 18:25:47 EEST

On Tue, 4 Apr 2000, Petr Kristan wrote:

> First recorded tracks were drifted against next. Drift time depends
> on buffer length. Why? Program can calculate diference from sample
> rate and buffer size. Or there is another problem.

Hmm, what were the exact command lines you used when recording?
Ecasound does try to sync tracks, but the are a few things that
can go wrong:

(a) first ecasound reads 'buffersize' samples from the monitor track(s)
    and fills soundcard output buffers with this data -
    nothing is written to output files
(b) at this point all soundcard devices are triggered at the same time
    (this is most accurate with OSS drivers if the card supports
(c) to compensate for possible sync-drift, ecasound checks
    how much samples have the soundcard devices processes so far
    (fetched directly from the driver-level) and forward/rewinds
    the output files based on this information

Problem is either with (b) or (c). In both cases, however, using
a small buffersize helps. You usually get good results with -b:128 and

> If we try only play one mono recorded track with ecasound, then there
> were weakly audiable cloops. Cloop bursts were repeated with
> frequency depended on buffer size. Then we try to play track with
> sox's play and sound was ok. We tried older version 1.6 ecasound with

Hmm, this is new. How about with aplay (comes with ALSA)?

Kai Vehmanen <> ---------------- CS, University of Turku .
 . audio software for linux ... 		 .
 . armchair-tunes mp3/wav/ra .. .

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