Hi there, newbie question, but I'm trying to figure out why a recording I made a few months ago has the occasional, quiet digital click (once every couple of minutes or so).

I assume it was because the buffer size was set ever so slightly too small, but it was only a stereo recording (using a MacBook Pro and Mackie 400f interface). Is this likely? I thought I had set the buffer size more than big enough, but am wondering if the DAW (Harrison Mixbus i.e. Ardour) or Jack re-set the buffer size to the minimum as a default, without me realising? At any rate I monitored through the interface alone, which is why I didn't notice anything during the session.

Is there any way to identify in reverse why these clicks might have been imparted to the recording? E.g. can I find out the settings that were used on the day? It just seems odd a new Mac couldn't cope with only two tracks of audio....

Thanks for any suggestions!

Clicking is usually cause by missing samples, and that could be because the buffer size is too small, and so it overflows, or it could be because a slave device isn't clocked correctly (not likely in a system with only one device -- the interface which must be a clock master), or it could be because the computer OS decides to go off and do something else for a moment, allowing the recording process to become a background task whch then gets corrupted.

I suspect the latter is the most likely in your case.

Was the wifi active, perhaps or some other background application that periodically decides to go off and check the hinternet or similar?

Hugh

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Technical Editor, Sound On Sound

Quote Hugh Robjohns:

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Was the wifi active, perhaps or some other background application that periodically decides to go off and check the hinternet or similar?

Hugh

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I don't think I ever connected to a network (the session was in a church) but I don't think I turned off AirPort either. During recording, I would have used expose to switch between mixer and editor in Ardour, as well as checking the Mackie console occasionally. Would this have compromised the recording?

Is there a guide to how I can optimise the Mac for audio performance? I definitely want to avoid this in the future!

you generally don;t need to.... they work fine out of the box....


i suspect the buffer size, which wouldn't have been heard on the day as you were hardware monitoring through the schmuckie..... not "off tape" from the mac....


i also suspect some of schmuckie's legendary "driver quality" and support.... (note this is dripping with sarcasm) .



that said, maybe the use of expose switching entire screens might have been a factor..... i've never tried that while tracking.... seems risky to me...... I simply use window menu's in the relevant DAW of the moment.... and avoid mucking about with stuff during tracking any way....

+1 on buffer. Whack it all the way up. No need for latency control in this situation.

BTW, you can now have fun zooming in and penciling out all those squared glitches or, as Hugh pointed out, if it is dropping samples, you won't be able to remedy this.

You also don't state what SR you were recording at and that could affect the system performance in similar ways.

ken

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I'm All Ears.

Quote ken long:

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+1 on buffer. Whack it all the way up. No need for latency control in this situation.

BTW, you can now have fun zooming in and penciling out all those squared glitches or, as Hugh pointed out, if it is dropping samples, you won't be able to remedy this.

You also don't state what SR you were recording at and that could affect the system performance in similar ways.

ken

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Yeah, as I said, I usually play it safe with buffer size, but am wondering if Jack/Ardour re-set it...

And yeah, i've certainly been having 'fun' removing them Except they're so quiet that they're often 'buried' in the wave image and I have to do it by ear. No obvious 'square' when zoomed in. Unless that means the clicks are to do with something else?

I recorded at 44.1k 24bit btw

Quote idris y draig:

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that said, maybe the use of expose switching entire screens might have been a factor..... i've never tried that while tracking.... seems risky to me...... I simply use window menu's in the relevant DAW of the moment.... and avoid mucking about with stuff during tracking any way....

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I'm new to Macs you see, so I couldn't resist! Is there no way to assign a safe amount of RAM/CPU to audio processing so that it's never neglected?

Quote Myles Eastwood:

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Is there no way to assign a safe amount of RAM/CPU to audio processing so that it's never neglected?

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That’s what the audio interface RAM buffers are supposed to do


Martin

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YewTreeMagic

Quote Martin Walker:

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That’s what the audio interface RAM buffers are supposed to do


Martin

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Oh yeah, I read your section in Digital Problems Practical Solutions, Martin! Are the interface RAM buffers different to the computer's RAM then? And does it mean my interface could have been to blame when my laptop became busy with other tasks?