RE: choppy audio recording
RE: choppy audio recording
- Subject: RE: choppy audio recording
- From: "Simmons, Aaron" <email@hidden>
- Date: Wed, 25 Nov 2009 14:41:09 -0500
- Acceptlanguage: en-US
- Thread-topic: choppy audio recording
Thanks for your response. I've posted a WAV version of the distorted audio in the same place (http://sites.google.com/site/paleozogt/home/choppy-audio).
I agree that it's probably a hardware issue. If I use a different headset it won't happen. It's a C-Media USB headset, btw. There's been lots of reports of this in the field, and I finally got ahold of one of the 'bad' headsets. Interestingly it doesn't happen with *all* C-Media headsets.
Incidentally, our app doesn't exhibit this behavior on Windows using the same 'bad' headset. But the API and drivers are so different, I'm not sure if this is a meaningful comparison. At any rate, somehow the problem is being dodged on Windows.
I have tried to get it to happen with other apps (ie, Audacity) but haven't been able to get it to happen. It's not an on-demand thing, though, so it's unclear if it's not happening or if I'm just not patient enough.
I will take a look at HALLab and whether we're using kAudioDeviceProcessorOverload. Thanks!
aaron
-----Original Message-----
From: coreaudio-api-bounces+asimmons=email@hidden [mailto:coreaudio-api-bounces+asimmons=email@hidden] On Behalf Of Jeff Moore
Sent: Wednesday, November 25, 2009 12:31
To: CoreAudio API
Subject: Re: choppy audio recording
I listened at the recording. You can clearly hear that the recording is not just glitching, it is actually repeating itself in small chunks. It also seemed that the glitches were not the same duration or spaced evenly. But it's hard to tell with an MP3 encoded version. The MP3 encoding also really prevents me from analyzing the content of the glitch.
At any rate, the sonic evidence would seem to point toward the hardware device as the source of the problem by virtue of the uneven timing of the glitches. But here are some things to look at:
- Test your app with other hardware. While it seems like this is a hardware issue on the surface, it could be somewhere else in the food chain. Testing with other hardware would be a good way to confirm or deny this.
- Test your hardware with other apps.
- Make sure your app is listening to kAudioDeviceProcessorOverload for when the HAL says that things have gone off the rails.
- Use the IO cycle telemetry window in HALLab (found in /Developer/Applications/Audio) to analyze what your app's IO cycle is up to. This is a good way to look at overloads and other problems and see what caused them. I've posted usage notes about this on this list previously.
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