Re: Not Setting Format results in multichannel playback success
Re: Not Setting Format results in multichannel playback success
- Subject: Re: Not Setting Format results in multichannel playback success
- From: Doug Wyatt <email@hidden>
- Date: Fri, 7 Jul 2006 13:26:54 -0700
On Jul 6, 2006, at 23:24 , Mike Hanna wrote:
I finally have playback of multichannel audio with code based on
PlayFile.cpp.
Using AudioFileGetProperty(), I load a file into a buffer:
XThrowIfError (AudioFileGetProperty(fAudioFile,
kAudioFilePropertyDataFormat, &propsize, &fFileFormat),
"AudioFileGetProperty");
I could not get sound when playing a multichannel file; I thought
it was because I wasn't using SetFormat(), but it apparently it
causes an exception, of which kind I don't know:
http://paste.lisp.org/display/22194
/*** using SetFormat seems to cause an exception, any idea why? ***/
I finally decided to comment-out any code that calls
SetNumberChannels() or SetSampleRate(). Removing these results in
successful playback of multichannel audio, any idea why?
/*** commenting-out these lines results in successful playback of
multichannel audio, why? ***/
XThrowIfError( fFileAU.SetFormat( kAudioUnitScope_Input, 0,
fFileFormat ), "SetFormat" );
// printf ("makeGraph file in: ");
// XThrowIfError( fFileAU.SetFormat( kAudioUnitScope_Output,
0, fFileFormat ), "SetFormat" );
// printf ("makeGraph file out: ");
These probably fail because fFileFormat is something other than
deinterleaved Float32.
// prepare the file AU for playback
// set its output channels
// XThrowIfError (fFileAU.SetNumberChannels
(kAudioUnitScope_Output, 0, fFileFormat.NumberChannels()),
"SetNumberChannels");
// set the output sample rate of the file AU to be the same
as the file:
// XThrowIfError (fFileAU.SetSampleRate
(kAudioUnitScope_Output, 0, fFileFormat.mSampleRate),
"SetSampleRate");
It's not clear why these should fail before connecting and
initialization. What's the error?
Doug
--
Doug Wyatt
Core Audio, Apple
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