Determine output latency?

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Determine output latency?

Ed Wildgoose-2
Hi, I am trying to get an estimate of the output latency of the current
jack audio.  I understand some of the limitations of this, but in fact a
fairly rough estimate will be acceptable in this case

Right now I have a client connected out to Brutefir, which in turn is
connected to the jack output ports where jack is using an alsa based
driver to an RME9632

If I call: jack_port_get_total_latency() after connecting my clients
output to Brutefir I get back the answer zero?  (Is this an
implementation issue with Brutefir?)

Given that I setup the jack server with a period size of 1024 samples
and 2 period, what I'm trying to get from the client is how to find out
that the latency is at least 2048 samples?  How can I query the jack
server for this?

I can ask the jack server for it's buffer size, and assume a known
number of periods, but it would be desirable to query for this
programmatically?

Thanks for any pointers?

Ed W
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Re: Determine output latency?

Paul Davis


On Fri, May 7, 2010 at 7:19 AM, Ed W <[hidden email]> wrote:
Hi, I am trying to get an estimate of the output latency of the current jack audio.  I understand some of the limitations of this, but in fact a fairly rough estimate will be acceptable in this case

Right now I have a client connected out to Brutefir, which in turn is connected to the jack output ports where jack is using an alsa based driver to an RME9632

If I call: jack_port_get_total_latency() after connecting my clients output to Brutefir I get back the answer zero?  (Is this an implementation issue with Brutefir?)

this is a limitation of the current latency API. i have a new proposal that i've been meaning to post for some time now (its really the last piece of the API puzzle before declaring "1.0").

the problem is that JACK can't trace the signal *through* Brutefir. it doesn't know that the signal that goes into Brutefir's input ports comes out from its output ports.

does this make the current latency API useless? well, not entirely, but yes, in this particular (and VERY common case), its close to it.

i'll try to post on my proposal ASAP.

--p



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