[ecasound] buffer logic

From: Patrick Shirkey <pshirkey@email-addr-hidden>
Date: Mon Sep 23 2013 - 11:28:07 EEST


I am using ecasound to run some tests with latency between jack and pa.

I am trying to track down a bottle neck on the pa side. There are are
couple of possibilities which are explained below (copied from the pa

The audio is accumulating in some buffer, and the JACK sink in
PulseAudio doesn't have any buffer, so it's not the sink. It could be
some other buffer in PulseAudio, or it could be a buffer in ecasound.

Saying that ecasound is configured with 64 frames/period isn't terribly
informative, because I don't know how ecasound handles the transfer from
the input to the output. Does it push the data immediately to the output
when it gets something from the input, or are both directions callback
based? If the former, then the data can accumulate in the stream buffer
in PA, and if the latter, then there has to be an intermediate buffer
between the input and the output in ecasound, and the data can
accumulate there.

Can someone shed some light on this issue from the ecasound perspective?

The graph and chain I am using is the folllowing:

jack_delay -> pa_source -> ecasound -> pa_sink -> jack_delay

ecasound -f:32,2,48000 -b:64 -i alsa -o alsa

Patrick Shirkey
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Received on Mon Sep 23 20:15:01 2013

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