Re: IO Proc doesn't behave as expected
Re: IO Proc doesn't behave as expected
- Subject: Re: IO Proc doesn't behave as expected
- From: Chris Rolfe <email@hidden>
- Date: Mon, 14 Mar 2005 23:57:04 -0800
On 3/12/05 11:59 AM, "Robert Grant" <email@hidden> wrote:
> There's something else going on here...
Thanks for the response (it gave me the spur to continue debugging...).
The problem seems to be my output unit initialization. I'm using a local
variable to set the output unit's format. I assumed that
AudioUnitSetProperty would copy the struct, but it appears to expect the
caller to retain the memory.
Assuming I'm not mistaken, is this by-design? Is it generally true of data
passed to AudioUnitSetProperty?
Chris
//=======================================================
// Code Example:
// !! BUG !! Local data. Call succeeds, but host callback generates garbage.
OSStatus setformat()
{
AudioStreamBasicDescription format = { 48000.0, type, flags, 4, 1, 4, 2, 32
};
OSStatus err = AudioUnitSetProperty (theUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Input,
0,
format,
sizeof(AudioStreamBasicDescription));
}
// Works! Static data. Call succeeds. Sine tones fill the air.
AudioStreamBasicDescription format = { 48000.0, type, flags, 4, 1, 4, 2, 32
};
OSStatus setformat()
{
OSStatus err = AudioUnitSetProperty (theUnit,
kAudioUnitProperty_StreamFormat,
kAudioUnitScope_Input,
0,
format,
sizeof(AudioStreamBasicDescription));
}
Chris
>
> Robert.
>
> On Mar 11, 2005, at 9:58 PM, Chris Rolfe wrote:
>
>> Taking for granted initialization, etc., can anyone suggest why
>> starting/sleeping/stopping an IO Proc works, but the same IO Proc might
>> produce garbage when start/stop are called from a Cocoa UI, a la:
>>
>>
>> This works fine:
>>
>> void start() { AudioOutputUnitStart (unit); }
>> void stop() { AudioOutputUnitStop (unit); }
>>
>> void test()
>> {
>> start();
>> usleep (4 * 1000 * 1000); // sleep this thread while audio
>> plays
>> stop();
>> }
>>
>> This sucks:
>>
>> -(void) startButton () { start() ; }
>> -(void) stopButton () { stop() ; }
>>
>> TIA,
>> Chris
>>
>>
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--
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equivalent to the conclusion; see, reasoning, circular.
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