Re: [Jack-Devel] Testing JACK and PA latency

On Wed, September 18, 2013 11:36 pm, Paul Davis wrote:
> there isn't any way to separately compute the "outbound" and "inbound"
> latency. in fact, jack_iodelay's message about the value to use for -I and
> -O is based on the not-entirely-defensible but somewhat reasonable
> assumption that the outbound and inbound latencies are symmetric.
>
> put differently, i don't think there is any way to do what you want.
> someone may prove me wrong.
>

It's a new one for me too so I'm not expecting a pre-existing solution.

This is part of a wider test procedure so I am trying to get a method that
can be considered robust and literal. I'm sure it is viable to calculate
the latency for each step in the process based on configuration settings
but in this case it will be *very* useful (and potentially lucrative for
everyone) to present a definitive result and test procedure.

Any ideas for how to go about it are welcome.

To recap I am seeking to define the i/o latency at any period size/sample
rate when an application that is dependant on PA is sending/receiving data
via JACK.

If anyone has thoughts on a method for tweaking the configuration settings
for both PA and JACK while running (automated) latency tests that would
also be very useful. Piece of cake right?



>
> On Wed, Sep 18, 2013 at 6:55 AM, Patrick Shirkey
> <[hidden]
>> wrote:
>
>>
>> On Wed, September 18, 2013 4:49 pm, Patrick Shirkey wrote:
>> > Hi,
>> >
>> > Can anyone recommend a rigorous procedure for verifying round trip
>> latency
>> > between i/o using a combination of both JACK and PA?
>> >
>> >
>>
>> I have the following setup:
>>
>> jack running in duplex mode (1024/48000/2)
>> pa connected to jack with sink/source plugins
>> skype* running via pa
>> jack_iodelay
>>
>> I have the following connections
>>
>>      jack_delay (out) -> pa jack source (1)
>>      system_in (1) -> jack_delay (in)
>>      system_in (1) -> pa jack source (1)
>>      pa jack sink -> system_out (1)
>>
>> I can hear the output signal from jack_delay in the skype call test
>> service.
>> I can hear the mic input in skype call test service
>> I can hear skype output in my speakers via jack system output
>>
>> I see the following info in jack_delay console messages:
>>
>>  22120.239 frames    460.838 ms total roundtrip latency
>>         extra loopback latency: 21096 frames
>>         use 10548 for the backend arguments -I and -O ??
>>
>>
>> However I don't think this setup is calculating latency details that I
>> am
>> looking for.
>>
>> I would like to retrieve the following info:
>>
>> 1: latency from jack system in -> pa_source -> skype in -> skype network
>> output (before the data is transmitted to the external receiver)
>>
>> 2: latency from skype network input (immediately data that is received
>> from external provider) -> pa_sink -> jack_system out
>>
>>
>> * skype is used for testing i/o via PA. Any other duplex app could also
>> be
>> used.
>>
>>
>>
>>
>>
>> --
>> Patrick Shirkey
>> Boost Hardware Ltd
>> 
>> Jack-Devel mailing list
>> [hidden]
>> http://lists.jackaudio.org/listinfo.cgi/jack-devel-jackaudio.org
>>
>


--
Patrick Shirkey
Boost Hardware Ltd

1379518192.27958_0.ltw:2, <57026.86.127.135.98.1379518182.squirrel at boosthardware dot com>