[linux-audio-user] what latency can I expect?

Jack O'Quin joq at io.com
Fri Jan 30 21:06:05 EST 2004

Atte André Jensen <atte at ballbreaker.dk> writes:

> It seems that I get quite stable performance by starting jack like
> this on my P4 2.4Ghz laptop with onboard i810:
> jackstart -R -v -d alsa -n 3 -p 256 -zt
> But what exactly does this translate to in terms of latency? 

Divide frame counts by (frames/second) to get seconds.  

Your input latency is 256/48000, 5.333 milliseconds.  The output
latency is three times that because of -n3, 16 msec.  This is the
latency due to buffering between the device and JACK.  Clients may
introduce additional latency depending on the processing they perform.
Well-behaved clients should report this extra latency for each of
their output ports.  There will also be some small but unknown
hardware latency due to the A/D and D/A converters.

> Should I expect more? 

I don't know.  Depends on many system-level hardware and software
performance and configuration options.

> I get almost the same performance under 2.4.23 with Andrew Morton's
> low-latency patched and 2.6.2 with or without the mm-patch.

That's probably pretty good then, though there are other things to
tune besides the kernel.

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