Re: How to capture audio generated by a render callback, iOS

Subject: Re: How to capture audio generated by a render callback, iOS
From: Tim Kemp <email@hidden>
Date: Tue, 04 Dec 2012 21:05:00 -0500

Thanks Alan. My other reply is held for moderation because it's too long.

I have mNumberBuffers = 2 at the moment. I think what's happened is that I've misunderstood how stereo audio works early on in developing my app, and I've inadvertently used multichannel audio instead. This question here: http://stackoverflow.com/questions/2450248/reading-audio-with-extended-audio-file-services-extaudiofileread led me to that conclusion. I think I need to rethink how I'm handling stereo audio to make this work.

I tried a small hack by just writing one of the two buffers in the ExtAudioFileWriteAsync call, and I got something out - a very static-y file with the actual audio I played buried in it. Will proceed in this direction.

Thanks for taking a look and for your sample code!

On 4 Dec 2012, at 18:28, Aran Mulholland wrote:

There is some code I wrote that has an example of recording using this here https://github.com/aranm/iPhone-ExtAudioFile-Record

Disclaimer: Dodgy

On Wed, Dec 5, 2012 at 6:48 AM, Tim Kemp <email@hidden> wrote:

As a follow-up, if I replace the calls to ExtAudioFileWriteAsync with the synchronous version then I get lots of -50 errors on every write. I believe that's a parameter error, so something isn't right in what I'm passing in.

I see the -50 on both the 'prime' call right after I create the file, then also every time the callback runs when I actually try to write the data.

Weirdly, by buffer size seems to vary around 470. I was expecting 512 length buffers. Could this be related?

Thanks

On 4 Dec 2012, at 11:07, Tim Kemp wrote:

> I'm having a little trouble getting this working. I have an EXC_BAD_ACCESS in the call to ExtAudioFileWriteAsync. My Googling around hints that it might be down to a bad ASBD, but I'm not sure what a good one looks like. I want to write LPCM to a CAF. (It's just for internal use in the app and for eventual pasting to the pasteboard if this makes a difference.)
>
> Here is how I set it up. Firstly, my output ASBD which works fine. This is used by the RemoteIO for actually producing sound from the speakers. Then _fileASBD is for the recorded file:

<snip>

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Follow-Ups:
- Re: How to capture audio generated by a render callback, iOS
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References:
	>How to capture audio generated by a render callback, iOS (From: Tim Kemp <email@hidden>)
	>Re: How to capture audio generated by a render callback, iOS (From: Gregory Wieber <email@hidden>)
	>Re: How to capture audio generated by a render callback, iOS (From: Tim Kemp <email@hidden>)
	>Re: How to capture audio generated by a render callback, iOS (From: Tim Kemp <email@hidden>)
	>Re: How to capture audio generated by a render callback, iOS (From: Aran Mulholland <email@hidden>)

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