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Archives for : February2013

Correcting Core Audio

A client unexpectedly hitting pause on a major project has me less employed than I’d like right now — yes, I’m available, ping me — so I’ve spent some time in the past few weeks cleaning up some corrections on Core Audio stuff here and there.

I went through the e-mailed errata I’ve received for Learning Core Audio and sent off an update to Pearson, although it’s not yet up on the book’s home page. The biggest fix here is a typo in the chapter 8 audio pass-through for Mac, which sometimes causes bad distortion depending on your selected input device. The bug was caused by mis-counted timestamps and apparently a race condition of which audio unit (input or output) got called first… all owing to the fact that I had set -1 as a flag value, and then did a comparison against 0 instead of -1. Anyways, if this is something that bit you, watch the book’s home page for an update, or just grab the updated code from my Dropbox. The zip has a CHANGES.txt with the other code fixes in this update.

The other thing I had to correct was my ambitious pitch-shifting web radio demo that I developed for my CocoaConf Portland talk. The effect stopped working in iOS 6.1, and fixing it led to a long engagement with the coreaudio-api mailing list and the use of an ADC support incident on my part.

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