[PD] meaning of delay(msec) and use callbacks in audio settings

[David Medine]

Basically these things have to do with performance.

'Use callbacks' has to do with how Pd communicates with your soundcard. 
There are two options, using callbacks, and blocking. In the callbacks 
scenario, your computer processes samples then asks the sound card to 
'call you back' when it's ready to receive those samples (i.e. when it 
is out of audio to play and needs some more). In the meantime, you can 
process more samples, or check out what's going on on CNN.com or whatever.

In the blocking method the computer hands the samples to the soundcard 
by calling a function and if the sound card is not ready, it 'blocks' 
meaning it stops your function in its tracks until it is ready to 
receive the data. Your thread (Pd) will halt until the function that 
sends the audio has finished.

Anybody out there, please correct me if I am spreading misinformation 
here, but this is my understanding of this distinction.

Delay(msec) is a delay between logical time (when your computer computes 
the audio) and real time (when the sound comes out the speaker). You 
want to have some head room here. I've seen really good setups get down 
to below 10ms (as low as 4) without any glitches, but usually you want 
much more time ~50ms or so.

On 2/17/2015 5:42 PM, Jonghyun Kim wrote:
>
> Fyi, I use jack on Linux for PD.
>
> On Feb 18, 2015 8:16 AM, "Jonghyun Kim" <agitato816 at gmail.com 
> <mailto:agitato816 at gmail.com>> wrote:
>
>     Hi list,
>
>     I would like to know about some features in audio settings.
>
>     I don't understand what mean these options.
>
>     *Delay(msec)* and *Use callbacks*
>
>     I googled these options, but still I don't understand. Is there
>     some document about it?
>
>     Thanks in advance,
>     akntk
>
>
>
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