[LAU] Lexicon Lambda USB - are my lockups due to the hardware or software?

[Len Ovens]

On Fri, 14 Apr 2017, Chris Caudle wrote:

> On Tue, April 11, 2017 9:11 am, Antony Gelberg wrote:
>> I also noticed when starting jack:
>> Apr 10 11:46:50 cubase pulseaudio[23745]: [pulseaudio] module-jack-sink.c:
>> JACK error >Cannot use real-time scheduling (RR/5)(1: Operation not
>> permitted)<
>> Apr 10 11:46:50 cubase pulseaudio[23745]: [pulseaudio] module-jack-sink.c:
>> JACK error >JackClient::AcquireSelfRealTime error<
>>
>> Although qjackctl reports that jackd *does* run with realtime scheduling.
>
> I just checked my system log when loading the jack-sink module and noticed
> the same thing:
> pulseaudio[30057]: [pulseaudio] module-jack-sink.c: JACK error >Cannot use
> real-time scheduling (RR/15)(1: Operation not permitted)<
> pulseaudio[30057]: [pulseaudio] module-jack-sink.c: JACK error
>> JackClient::AcquireSelfRealTime error
>
> It doesn't seem to cause any problems, I  just played a couple of youtube
> videos with no underruns.

Yes I have the same thing.

It does cause problems at low latency (jack at 16/2 for example). 
Actually, I should clarify, low latency depends on the application talking 
to PA, Skype for example needs jack to run at 128/2 (at 48000) to function 
properly.

module-jack-sink/source are "example" code. Means not well tested or 
complete. They try to pull pulse into the same latency as jack is running 
(watch cpu used by PA as latency in jack changes). Those two modules need 
some love which I don't think is going to come from the original author. I 
would suggest that these modules need to include some buffering. My 
fondest wish would be for PA to see jackd as a device with the same kind 
of configuration as ALSA devices (and protections... maybe more)

I am not sure if merely adding a ring buffer would fix that or not. (might 
be a start though) I have not personally looked at the code.


--
Len Ovens
www.ovenwerks.net