Apple Lossless compression in AudioUnit
Apple Lossless compression in AudioUnit
- Subject: Apple Lossless compression in AudioUnit
- From: Tom Mitchell <email@hidden>
- Date: Wed, 7 Oct 2009 11:25:30 -0400
I'm having trouble updating a test program that worked in 10.4
(Tiger). This program creates audio input data programmatically (a
sine wave), passes the data through an ALAC AudioUnit using
AudioUnitRender, then stores the resulting data in a QuickTime movie
using AddMediaSample2.
This program worked in 10.4, succeeds but generates no sound in 10.5
(Leopard), and gets an error (-50) on the AudioUnitRender in 10.6
(Snow Leopoard).
The program successfully writes a QuickTime movie file with a single
audio track (on all three OSs) when it skips the AudioUnitRender step.
Some basic questions:
1. Does the general approach of using an AudioUnit to compress data
seem appropriate at this time? The code is about 5 years old, and
other support may be available at this time.
2. I understand from searching this list that the -50 error code from
AudioUnitRender indicates an incorrect parameter in the
AudioStreamBasicDescription. Is there a way to tell which parameter
(s)? I couldn't find anything, but that might be very helpful.
I have worked with sample programs like WhackedTV and ConvertFile
which do similar but different things. My ASBD looks right when
compared to what I see in the debugger in those programs.
Thanks in advance for any help or advice.
Tom Mitchell
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