Feature request - 2 differents settings for buffer size

[Patrick Spadrille]

I had some trouble using audio cues. My workspace contains audio cues, mic cues and video cues. I know, that's a lot but it's pretty close to work perfectly. The only problem is that i have to reduce buffer size in order to have no delay in the mic cues. When i do that, i create interferences in the audio. BUT, if i don't use audio cues in Qlab and instead use MainStage on the same computer with the same audio card for the mikes, i can use a bigger buffer size on Qlab and a smaller buffer size on MainStage and then everything works alright. 

So my feature request is : why not have 2 settings for buffer size? Audio cue buffer size and Mic cue buffer size. That's pretty much what i do using MainStage. But using MainStage is far from the convenience of using mic cues right inside Qlab, with the possibility of fade cues, routing,... 

Dear Qlab developpers, does that seems doable? 

[Christopher Ashworth]

Hi Patrick,

This is impossible. Audio devices have only one buffer size at a time. As far as I understand how CoreAudio works, It is not even possible to do what you describe using mainstage, because the buffer size is one setting on the physical device which all applications must share at the same time.

(mobile)

--

[Patrick Spadrille]

Hi Christopher,

I'm afraid i have to tell you that this is very possible. :-). It works just like i said. First some facts : If i choose 32 as buffer size in Qlab, i have audio interferences but no delay in the mikes. If i choose 512 as a buffer size in Qlab i have no interference but a big delay in the mikes. In MainStage the same delay is happening if i choose 512 and disappear if i choose 32. In my test i run at the same time Qlab with a buffer of 512 and MainStage with a buffer of 32 and everything works fine. No audio interferences from Qlab and no delay from MainStage. Yes, i use the same audio card (Motu Ultralite Hybrid MKIII). So that's maybe theoretically not possible but in practice i assure that it works very fine.

[Chris Ashworth]

I'm afraid i have to tell you that this is very possible. :-). It works just like i said. First some facts : If i choose 32 as buffer size in Qlab, i have audio interferences but no delay in the mikes. If i choose 512 as a buffer size in Qlab i have no interference but a big delay in the mikes. In MainStage the same delay is happening if i choose 512 and disappear if i choose 32. In my test i run at the same time Qlab with a buffer of 512 and MainStage with a buffer of 32 and everything works fine. No audio interferences from Qlab and no delay from MainStage. Yes, i use the same audio card (Motu Ultralite Hybrid MKIII). So that's maybe theoretically not possible but in practice i assure that it works very fine.

Hm, interesting. It looks like yes this can be set differently for different running processes, which is unexpected to me, since these are supposed to represent physical properties of the device.  

However, as far as I can tell, this value can NOT be different for the same process, i.e. one copy of QLab can only set this value to one thing.

So it’s still impossible, as far as I can tell, to allow you to set a different buffer size for the same device within the same program.

-C

[Patrick Spadrille]

Isn't there a possibility to think "out of the box"? A way to separate technically these stuff into two pieces of softwares running 2 different processes talking to each other and all with one interface. After all that's almost what i do with MainStage and Qlab (but very painfully) so why not ? I'm sure i'm not the first who encounter the technical limit of mic cues, that could a way to solve it. 

[Chris Ashworth]

How about use two different audio devices? :-)

This is not something that will be changing on the QLab side; it’s just not the way CoreAudio is designed to work.

[Patrick Spadrille]

Why would i need 2 audio devices. As far as i know, mic cues doesn’t work with two audio devices. Or maybe agregate devices? But the problem would be the same, isn’t it? I can’t set 2 different buffer size in Qlab for the same device.

[Chris Ashworth]

Why would i need 2 audio devices. 

Yes.

As far as i know, mic cues doesn’t work with two audio devices. Or maybe agregate devices? 

Yes, they do work with aggregates.

But the problem would be the same, isn’t it? I can’t set 2 different buffer size in Qlab for the same device.--

If the problem is that you need one buffer size for audio cues and one for mic cues, those will need to be two different devices. We can’t change that inside QLab.

-C