[PD] DSP and Gem in the same instance of Pd

[cyrille henry]

Le 31/03/2016 11:19, Roman Haefeli a écrit :
> On Thu, 2016-03-31 at 11:13 +0200, Roman Haefeli wrote:
>> Hey all
>>
>> It's a well know issue and the solution has been discussed many times:
>> When you're using audio and Gem rendering, it's wise to separate those
>> two into their own instance of Pd.
>>
>> I'm working on a project that does both, audio processing and Gem
>> rendering. The OpenGL rendering is very light-weight and does only
>> require minimal resources. Also the audio part uses a fraction of the
>> available CPU power. What I observe is that I get a zipping noise for
>> ~15 seconds, then clean audio for another 15 seconds before the zipping
>> noise returns. The zipping noise occurs only when Gem rendering is
>> turned on.
>>
>> To me it looks like the problem is not related to limited resources,
>> rather it seems that both, OpenGL and audio rendering, are tied to their
>> respective clock and those clocks are not coupled and thus are not
>> completely in sync.
>>
>> I know I could put both parts into their own instances of Pd and that's
>> what I'll do if there is no resolution, but for convenience reasons I'd
>> prefer to have only one patch in one instance of Pd. Now, is there a way
>> to loosen the coupling to OpenGL clock (is it the same as the monitor
>> clock?) so that audio is not affected? I don't care about any
>> side-effects like tearing (it won't be visible anyway for the kind of
>> image).
>
> BTW: Why does the graphics rendering|clock have precedence over the
> audio rendering (at least, it seems to be like that in Pure Data/Gem)? I
> guess most softwares do it the other way around, since clicks are much
> more noticeable than a frame being a few milliseconds late.

Gem have no precedence over audio : they both have the same priority.
when having priorities on audio, the openGL rendering did not have fixed frame rate, and it's not possible any-more to have smooth hight speed movement.

So, i like the way it is, even if it cause implementation problem.

one possible explanation of your problem is that you are rendering a 60 fps, and that openGL is sync on the 60fps screen.
You can have jitter between the 2 different 60fps clock. If Gem is waiting for the screen, then everything (including audio) is on pause.

if this is the cause of your problem, then reduce Gem fps to 59, or remove openGL syncro (sync to vblank).


cheers
c



>
> Roman
>
>
>
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