Re: More Glitches

• Subject: Re: More Glitches
• From: Jeremy Sagan <email@hidden>
• Date: Mon, 14 Feb 2005 21:40:43 -0500
• Delivered-to: email@hidden
• Delivered-to: email@hidden

Glitches that don't correspond to over loads can be caused by lots of things. The usual cause is supply chain issues, but there have been a handful that are hardware/driver related.

It's tough to say anything more without knowing more about the situation.

On Feb 14, 2005, at 3:39 PM, Ethan Funk wrote:

So this implies that the HAL is getting all the data from me that it needs and getting it on time to keep the device well feed, correct? What does that leave for a source of a glitch? Something driver related on the interface between the HAL and the actual device? The source audio buffers that my IO cycle pulls from are huge, so I don't thinks the glitches are coming from the feeder threads - I am showing a typical feeder lead of between 10 and 15 seconds at all times.

Thanks for the help
Ethan...

On Feb 14, 2005, at 15:35, Jeff Moore wrote:

The HAL only sends overload notifications when it detects them as part of the normal execution of the house keeping code at the end of each IO cycle. The HAL doesn't have any magical insight, so if you are getting glitches without a corresponding overload, it would imply that the glitching isn't related to the time being spent on the IO thread.

On Feb 14, 2005, at 12:58 PM, Ethan Funk wrote:

In my eternal hunt for the source of audio glitching, I have added the following code to my project to I can get a message on each HAL output processor overload event. However, I'm not getting any messages, even through I hear glitches. Am I doing something wrong in setting up notification or is it possible that the glitches are due to something else?

Here is my code for the callback: msg is a Boolean I set to true for debugging

OSStatus HALOverloadListener(AudioDeviceID inDevice, UInt32 inChannel, Boolean isInput, AudioDevicePropertyID inPropertyID, void *inRefCon)
{
Distributor *output = (Distributor *)inRefCon;

if(msg){
output_map_ptr dp;
string dataStr = "unknown";
// find the output in the output distributer list
pthread_mutex_lock( &oMutex );
for (dp=outputMap.begin(); dp!=outputMap.end(); dp++){
if(&((*dp).second) == output)
dataStr = (*dp).first;
}
pthread_mutex_unlock( &oMutex );
// print message
fprintf(stdout, " MESSAGE: Processor Overload on %s output, bus #%ld.\n", dataStr.c_str(), inChannel);
fprintf(stdout, "ae>");
fflush(stdout);
}
return noErr;
}


Then I register the call back just before AU Initialization deep in my audio setup procedure:

// set up notification of processor overload
err = AudioDeviceAddPropertyListener(devID, 0, FALSE, kAudioDeviceProcessorOverload, HALOverloadListener, this);
if (err)
return false;

// initialize the HALoutput AU
err = AudioUnitInitialize(outHALUnit);
if (err)
return false;

There is NO error when I add the property listener. Any insight would be appreciated!
Ethan...

--

Jeff Moore
Core Audio
Apple


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