19 Sep
2013
19 Sep
'13
11:39 a.m.
On Thu, September 19, 2013 7:19 pm, Hartmut Noack wrote:
--
Patrick Shirkey
Boost Hardware Ltd
Am 19.09.2013 10:46, schrieb Patrick Shirkey:
This is entirely professionally motivated and will also have major
benefits to academia too. I'm seeking suggestion on how to go about it not
arguments for why or if this is a useful thing to do... ;-)
Moving this thread to LAU as it seems to be a
more generic issue now:
I am testing the round trip latency when using PA and JACK together. I
have the following connection graph:
jack_system (in) -> pa_source (in) -> audacity (in) -> audacity (out) ->
pa sink (out) -> jack_system (out)
Unless your research is completely academic I do not see a practical use
for its results on the user-side. For Audacity latency is not a big
issue.
You can replace audacity with *any* application that can provide (near) 0
internal latency and full duplex pass through.
It does not build for realtime-application rather for
offline
editing, audio-restauration etc, in that field a latency of 100ms is
still OK....
In this case I have a hard limit of 20ms round trip latency from mic in to
speaker out and I would like to test the combination of JACK and PA to
determine where or if there are bottlenecks in the signal flow.
Audacity is run in pass through mode with
internal latency set to 0.
I would like to measure the round trip latency from jack_system (in) to
jack_system (out)
This is a slightly unusual request but it is actually a reasonably
important measurement in the bigger scheme of things.
Does anyone have any suggestions?
Ideally I would like to get accurate measurements for both input and
output latency.
input:
jack_system (in) -> pa_source (in) -> audacity (in)
output:
audacity (out) -> pa sink (out) -> jack_system (out)
So a tool that allowed me to measure the latency between every node on
the
graph would be perfect.
Obviously made alot harder by mixing PA and JACK together. I have tried
jack_iodelay but it does not measure the input signal from the mic
instead
it provides it's own signal.
I suppose I could modify jack_iodelay to accept an input signal as the
starting point for the latency graph but I have not looked into the code
yet to see how tricky that would be.
--
Patrick Shirkey
Boost Hardware Ltd
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