Thanks David for your answer.

I understand what mean audio buffer and block size. Now I'm on Linux with Jack backend, and the block size controlled by jack. I know how to change the block size with [block~] or [switch~] in sub-patch.

But I still don't understand the difference between Callback scenario and Block method. I think that I don't know what is Callback in audio settings. I searched about that, but I couldn't see good answer for me.

Thanks in advance,

akntk

On Wed, Feb 18, 2015 at 11:26 AM, David Medine <dmedine@ucsd.edu> wrote:

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@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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