Re: Gradual crackling/stuttering during audio capture
Re: Gradual crackling/stuttering during audio capture
- Subject: Re: Gradual crackling/stuttering during audio capture
- From: Jeff Moore <email@hidden>
- Date: Sat, 24 Jul 2010 13:10:11 -0700
When I listened to the file, it did indeed sound like a clock was drifting somewhere. But, when I took a look at the signal in a waveform viewer, I was only able to see the occasional spike of a couple of samples here and there. I didn't see anything obvious that would be glitching at the rate that I heard in the signal. So, my bet is that many of the glitches are signal sample in length and not that far off from where the sample should be such that it doesn't show up as distortion to the waveform.
At any rate, I'm not familiar with the interface in question, but it appears to be a class compliant device. Because two different apps appear to show the same problem and the telemetry doesn't show anything unusual, it probably implicates something in how the device is interacting with the class driver as the source of the glitches.
The best thing to do is to file a bug so we can take a look at it.
--
Jeff Moore
Core Audio
Apple
On Jul 24, 2010, at 5:33 AM, Rob Watson wrote:
> I'm using CoreAudio (wrapped in MTCoreAudio) to record from an interface called a Maya44 USB. It's a pretty typical, 4-in 4-out audio interface.
>
> I have spent the last few days trying to work out why recordings using this interface deteriorate in quality after about 45 seconds. Everything is fine at first, but then crackling/popping gradually sets in.
>
> This happens in my own code, and I assumed it was a bug in my audio processing code. But then I tried to record using Audacity and got exactly the same effect. Here is a short example .WAV file (recorded in Audacity)
> http://79.125.10.27/downloads/stutter.wav
>
> Because of the gradual onset it sounds like some kind of sample-rate or clock drift, but I don't know how I could affect any related parameters. I've also tried analysing using the telemetry window in HALLAB, but there is no overloading or dubious cycles highlighted.
>
> Any pointers on where to start here would be greatly appreciated :)
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