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Re: Monitoring input level

Thanks for the tips.
I've written a spike, according to the link you mentioned.

I can get it to all start up OK (that is, no errors), but I'm not getting anything for my levels. Just 'infinity'.
I (perhaps wrongly) didn't setup a channel map (hoping the default is OK), or an input proc (as I don't want to actually DO anything with the data).
Is an input proc required, even if I'm not wanting to save/play the audio?

In the interest of keeping one thread only: Karim Morsy also replied with the idea that I might be able to setup a link from AUHAL (input) -> mixer -> AUHAL (output), but the docs say that you can only have one output unit in a graph. I tried to create another unit using the same component description, but got error -10862 (which I cannot see doco for).

I've posted the code below, for reference. Hope it's not too much to wade through. If you're looking for where I start things rolling, it's at a method called monitorDevice.

---
Neil Clayton





//
//  AudioPreview.m
//  iShowU
//
//  Created by Neil Clayton on 18/06/2006.
//  Copyright 2006 __MyCompanyName__. All rights reserved.
//

#import "AudioPreview.h"
#import "DebugMacros.h"
#import "NSUtils.h"
#import "AudioToolbox/AudioFormat.h"
#import <AudioUnit/AudioUnitParameters.h>
#import <AudioUnit/AudioUnitProperties.h>
#import "CAStreamBasicDescription.h"

#define checkErr( err) \
if(err) {\
	OSStatus error = static_cast<OSStatus>(err);\
		fprintf(stderr, "Error: %ld ->  %s:  %d\n",  error,\
				__FILE__, \
				__LINE__\
				);\
					fflush(stdout);\
}


@implementation AudioPreview

- (id) init {
	self = [super init];
	return self;
}

- (void) dealloc {
	[self stopPreview];
	[super dealloc];
}

- (void) enableIO {
	UInt32 enableIO;
	
	//When using AudioUnitSetProperty the 4th parameter in the method
	//refer to an AudioUnitElement.  When using an AudioOutputUnit
	//the input element will be '1' and the output element will be '0'.
	
	enableIO = 1;
	AudioUnitSetProperty(inputUnit,
						 kAudioOutputUnitProperty_EnableIO,
						 kAudioUnitScope_Input,
						 1, // input element
						 &enableIO,
						 sizeof(enableIO));
	
	enableIO = 0;
	AudioUnitSetProperty(inputUnit,
						 kAudioOutputUnitProperty_EnableIO,
						 kAudioUnitScope_Output,
						 0,   //output element
						 &enableIO,
						 sizeof(enableIO));
}

- (void) createHALAU {
ComponentDescription desc;
desc.componentType = kAudioUnitType_Output;
desc.componentSubType = kAudioUnitSubType_HALOutput;
desc.componentManufacturer = kAudioUnitManufacturer_Apple;
desc.componentFlags = 0;
desc.componentFlagsMask = 0;

OSStatus err = AUGraphNewNode(auGraph, &desc, 0, NULL, &inputNode);
checkErr(err);
// err = AUGraphNewNode(auGraph, &desc, 0, NULL, &outputNode);
// checkErr(err);
err = AUGraphGetNodeInfo(auGraph, inputNode, NULL, NULL, NULL, &inputUnit);
checkErr(err);
}

- (void) createMixer {
OSStatus err = noErr;

ComponentDescription mixer;
mixer.componentType = kAudioUnitType_Mixer;
mixer.componentSubType = kAudioUnitSubType_MatrixMixer;
mixer.componentManufacturer = kAudioUnitManufacturer_Apple;
mixer.componentFlags = 0;
mixer.componentFlagsMask = 0;

err = AUGraphNewNode(auGraph, &mixer, 0, NULL, &mixerNode);
checkErr(err);
err = AUGraphGetNodeInfo(auGraph, mixerNode, NULL, NULL, NULL, &mixerUnit);
checkErr(err);
}

- (void) connectAUs {
OSStatus err = AUGraphConnectNodeInput(auGraph, mixerNode, 0, inputNode, 0);
checkErr(err);
err = AUGraphConnectNodeInput(auGraph, inputNode, 1, mixerNode, 0);
checkErr(err);
err = AUGraphUpdate(auGraph, NULL);
checkErr(err);
}


- (void) setDevice:(AudioDeviceID)deviceId {
    UInt32 size;
    OSStatus err = noErr;
    size = sizeof(AudioDeviceID);
	
    err = AudioUnitSetProperty(inputUnit,
							  kAudioOutputUnitProperty_CurrentDevice,
							  kAudioUnitScope_Global,
							  0,
							  &deviceId,
							  sizeof(deviceId));
	checkErr(err);
	
	// Setup the StreamFormat for element 1 - the input element
	CAStreamBasicDescription DeviceFormat;
    CAStreamBasicDescription DesiredFormat;
	size = sizeof(CAStreamBasicDescription);
	
	//Get the input device format
    err = AudioUnitGetProperty (inputUnit,
						  kAudioUnitProperty_StreamFormat,
						  kAudioUnitScope_Input,
						  1,
						  &DeviceFormat,
						  &size);
	checkErr(err);
	
    //set the desired format to the device's sample rate
    DesiredFormat.mSampleRate = DeviceFormat.mSampleRate;
	
	//set format to output scope
    err = AudioUnitSetProperty(inputUnit,
						 kAudioUnitProperty_StreamFormat,
						 kAudioUnitScope_Output,
						 1,
						 &DesiredFormat,
						 sizeof(CAStreamBasicDescription));
	checkErr(err);
}


- (void) enableMetering {
// turn on metering
UInt32 meteringMode = 1;
OSStatus err = AudioUnitSetProperty(mixerUnit, kAudioUnitProperty_MeteringMode, kAudioUnitScope_Global, 0, &meteringMode, sizeof(meteringMode) );
checkErr(err);
}

- (void) setVolumes {
// Not sure if I need to do this or not. It's had no effect so far, but did within ComplexPlayThru (when I modified it to have a mixer)
// // Enable the mixer input's and output's
// OSStatus err = AudioUnitSetParameter(mixerUnit, kMatrixMixerParam_Enable, kAudioUnitScope_Input, 0, 1, 0);
// checkErr(err);
// err = AudioUnitSetParameter(mixerUnit, kMatrixMixerParam_Enable, kAudioUnitScope_Output, 0, 1, 0);
// checkErr(err);
//
// // Set global volume
// err = AudioUnitSetParameter(mixerUnit, kMatrixMixerParam_Volume, kAudioUnitScope_Global, 0, 1, 0);
// checkErr(err);
//
// // Set master volume
// err = AudioUnitSetParameter(mixerUnit, kMatrixMixerParam_Volume, kAudioUnitScope_Global, 0xFFFFFFFF, 1, 0);
// checkErr(err);
//
// // Set input and output volumes
// err = AudioUnitSetParameter(mixerUnit, kMatrixMixerParam_Volume, kAudioUnitScope_Input, 1, 1, 0);
// checkErr(err);
// err = AudioUnitSetParameter(mixerUnit, kMatrixMixerParam_Volume, kAudioUnitScope_Output, 0, 1, 0);
// checkErr(err);
}

- (void) monitorDevice:(MTCoreAudioDevice*)aDevice {
	[self stopPreview];

	NewAUGraph(&auGraph);
	OSStatus err = AUGraphOpen(auGraph);
	checkErr(err);

	[self createHALAU];
	[self createMixer];
	[self connectAUs];	

	err = AUGraphInitialize(auGraph);
	checkErr(err);

	[self enableIO];
	[self setDevice:[aDevice deviceID]];
	[self setVolumes]; // doesn't do anything at present
	[self enableMetering];
	
	[self startPreview];
}

- (void)idleTimer:(NSTimer*)timer {
OSStatus err;

float amps[2];
err = AudioUnitGetParameter(mixerUnit, kMatrixMixerParam_PostAveragePower, kAudioUnitScope_Input, 0, &amps[0]);
checkErr(err);

err = AudioUnitGetParameter(mixerUnit, kMatrixMixerParam_PostPeakHoldLevel, kAudioUnitScope_Input, 0, &amps [1]);
checkErr(err);

currentAmps = amps[0];
peakAmps = amps[1];

NSLog(@"Got average power %f and peak power %f", currentAmps, peakAmps);
}

- (void) stopPreview {
	if(previewTimer) {
		[previewTimer invalidate];
		[previewTimer release];
		previewTimer = nil;
		OSStatus err = AUGraphStop(auGraph);
		if(err != noErr) {
			[self log:@"Error stopping AU graph, %d", err];
		}
	}
}

- (void) startPreview {
if (previewTimer == nil) {
previewTimer = [[NSTimer alloc] initWithFireDate:[NSDate date]
interval:.05
target:self
selector:@selector(idleTimer:)
userInfo:nil repeats:YES];
[[NSRunLoop currentRunLoop] addTimer:previewTimer forMode:NSDefaultRunLoopMode];
OSStatus err = AUGraphStart(auGraph);
if(err != noErr) {
[self log:@"Error starting AU graph, %d", err];
}
}
}


@end

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References: 
 >Monitoring input level (From: Neil Clayton <email@hidden>)
 >Re: Monitoring input level (From: Neil Clayton <email@hidden>)
 >Re: Monitoring input level (From: Jeff Moore <email@hidden>)



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