Re: [LAU] Estimating JACK latency

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To: <linux-audio-user@...>
Date: Thursday, May 3, 2012 - 2:27 am

On Tue, Apr 17, 2012 at 05:09:52PM +0000, Fons Adriaensen wrote:

Thanks for clarifying this.

I understand that the round trip delay for the soundcard is the sum
of capture port latency and playback port latency, plus whatever
additional delay is associated with the AD/DA converters.

However I see what appears to be a discrepency for
the latencies reported by jackd (2 + 2 periods roundtrip)
and by jack_lsp -l (1 + 2 periods round trip).
This is for jackd2.

jackd says:

configuring for 44100Hz, period = 1024 frames (23.2 ms), buffer = 2 periods
ALSA: final selected sample format for capture: 32bit integer little-endian
ALSA: use 2 periods for capture
ALSA: final selected sample format for playback: 32bit integer little-endian
ALSA: use 2 periods for playback

However, jack_lsp -l says:

system:capture_1
port latency = 1024 frames
port playback latency = [ 0 0 ] frames
port capture latency = [ 1024 1024 ] frames
system:capture_2
port latency = 1024 frames
port playback latency = [ 0 0 ] frames
port capture latency = [ 1024 1024 ] frames
system:playback_1
port latency = 2048 frames
port playback latency = [ 2048 2048 ] frames
port capture latency = [ 0 0 ] frames
system:playback_2
port latency = 2048 frames
port playback latency = [ 2048 2048 ] frames
port capture latency = [ 0 0 ] frames

Is this inconistent, or is there some other explanation?

> If you masure it using jack_delay you will in most cases find a value

Great to have these details available for unschooled
developers as myself!

Regards,

Joel

> Ciao,

--
Joel Roth
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Messages in current thread:
[LAU] Estimating JACK latency, S. Massy, (Mon Apr 16, 7:33 pm)
Re: [LAU] Estimating JACK latency, Paul Davis, (Mon Apr 16, 8:54 pm)
Re: [LAU] Estimating JACK latency, Joel Roth, (Sun May 13, 12:21 pm)
Re: [LAU] Estimating JACK latency, Paul Davis, (Sun May 13, 12:46 pm)
Re: [LAU] Estimating JACK latency, S. Massy, (Mon Apr 16, 9:24 pm)
Re: [LAU] Estimating JACK latency, Fons Adriaensen, (Tue Apr 17, 5:10 pm)
Re: [LAU] Estimating JACK latency, Joel Roth, (Thu May 3, 2:52 am)
Re: [LAU] Estimating JACK latency, Fons Adriaensen, (Thu May 3, 10:15 am)
Re: [LAU] Estimating JACK latency, S. Massy, (Thu May 3, 4:54 pm)
Re: [LAU] Estimating JACK latency, Joel Roth, (Thu May 3, 8:36 pm)
Re: [LAU] Estimating JACK latency, Joel Roth, (Thu May 3, 2:27 am)
Re: [LAU] Estimating JACK latency, Robin Gareus, (Thu May 3, 8:21 am)
Re: [LAU] Estimating JACK latency, Paul Davis, (Mon Apr 16, 9:38 pm)