How to programmatically sense the iPhone mute switch?

I can't seem to find in the SDK how to programatically sense the mute button/switch on the iPhone. When my app plays background music, it responds properly to the volume button without me having any code to follow that but, when I use the mute switch, it just keeps playing away.

How do I test the position of mute?

(NOTE: My program has its own mute switch, but I'd like the physical switch to override that.)

Thanks, JPM. Indeed, the link you provide leads to the correct answer (eventually. ;) For completeness (because S.O. should be a source of QUICK answers! )...

// "Ambient" makes it respect the mute switch
// Must call this once to init session
if (!gAudioSessionInited)
{
    AudioSessionInterruptionListener    inInterruptionListener = NULL;
    OSStatus    error;
    if ((error = AudioSessionInitialize (NULL, NULL, inInterruptionListener, NULL)))
    {
        NSLog(@"*** Error *** error in AudioSessionInitialize: %d.", error);
    }
    else
    {
        gAudioSessionInited = YES;
    }
}

SInt32  ambient = kAudioSessionCategory_AmbientSound;
if (AudioSessionSetProperty (kAudioSessionProperty_AudioCategory, sizeof (ambient), &ambient))
{
	NSLog(@"*** Error *** could not set Session property to ambient.");
}

I answered a similar question here (link). The relevant code:

 -(BOOL)silenced {
     #if TARGET_IPHONE_SIMULATOR
         // return NO in simulator. Code causes crashes for some reason.
         return NO;
     #endif

    CFStringRef state;
    UInt32 propertySize = sizeof(CFStringRef);
    AudioSessionInitialize(NULL, NULL, NULL, NULL);
    AudioSessionGetProperty(kAudioSessionProperty_AudioRoute, &propertySize, &state);
    if(CFStringGetLength(state) > 0)
            return NO;
    else
            return YES;

    }

Some of the code in other answers (including the accepted answer) may not work if you aren't in the ambient mode, where the mute switch is respected.

I wrote the routine below to switch to ambient, read the switch, and then return to the settings I need in my app.

-(BOOL)muteSwitchEnabled {

#if TARGET_IPHONE_SIMULATOR
    // set to NO in simulator. Code causes crashes for some reason.
    return NO;
#endif

// go back to Ambient to detect the switch
AVAudioSession* sharedSession = [AVAudioSession sharedInstance];
[sharedSession setCategory:AVAudioSessionCategoryAmbient error:nil];

CFStringRef state;
UInt32 propertySize = sizeof(CFStringRef);
AudioSessionInitialize(NULL, NULL, NULL, NULL);
AudioSessionGetProperty(kAudioSessionProperty_AudioRoute, &propertySize, &state);

BOOL muteSwitch = (CFStringGetLength(state) <= 0);
NSLog(@"Mute switch: %d",muteSwitch);

// code below here is just restoring my own audio state, YMMV
_hasMicrophone = [sharedSession inputIsAvailable];
NSError* setCategoryError = nil;

if (_hasMicrophone) {
    
    [sharedSession setCategory: AVAudioSessionCategoryPlayAndRecord error: &setCategoryError];
    
    // By default PlayAndRecord plays out over the internal speaker.  We want the external speakers, thanks.
    UInt32 ASRoute = kAudioSessionOverrideAudioRoute_Speaker;
    AudioSessionSetProperty (kAudioSessionProperty_OverrideAudioRoute,
                             sizeof (ASRoute),
                             &ASRoute
                             );
}
else
    // Devices with no mike don't support PlayAndRecord - we don't get playback, so use just playback as we don't have a microphone anyway
    [sharedSession setCategory: AVAudioSessionCategoryPlayback error: &setCategoryError];

if (setCategoryError)
    NSLog(@"Error setting audio category! %@", setCategoryError);

return muteSwitch;
}

To find out the state of the mute switch and the volume control I wrote these two functions. These are ideal if you wish to warn the user before they try creating audio output.

-(NSString*)audioRoute
{
	CFStringRef state;
	UInt32 propertySize = sizeof(CFStringRef);
	OSStatus n = AudioSessionGetProperty(kAudioSessionProperty_AudioRoute, &propertySize, &state);
	if( n )
	{
		// TODO: Throw an exception
		NSLog( @"AudioSessionGetProperty: %@", osString( n ) );
	}
	
	NSString *result = (NSString*)state;
	[result autorelease];
	return result;
}

-(Float32)audioVolume
{
	Float32 state;
	UInt32 propertySize = sizeof(CFStringRef);
	OSStatus n = AudioSessionGetProperty(kAudioSessionProperty_CurrentHardwareOutputVolume, &propertySize, &state);
	if( n )
	{
		// TODO: Throw an exception
		NSLog( @"AudioSessionGetProperty: %@", osString( n ) );
	}
	return state;
}

-(BOOL)isDeviceMuted
{
 CFStringRef state;
 UInt32 propertySize = sizeof(CFStringRef);
 AudioSessionInitialize(NULL, NULL, NULL, NULL);
 AudioSessionGetProperty(kAudioSessionProperty_AudioRoute, &propertySize, &state);
 return (CFStringGetLength(state) > 0 ? NO : YES);
}

I followed the general theory here and got this to work http://inforceapps.wordpress.com/2009/07/08/detect-mute-switch-state-on-iphone/

Here is a recap: Play a short silent sound. Time how long it takes to play. If the mute switch is on, the playing of the sound will come back much shorter than the sound itself. I used a 500ms sound and if the sound played in less than this time, then the mute switch was on. I use Audio Services to play the silent sound (which always honors the mute switch). This article says that you can use AVAudioPlayer to play this sound. If you use AVAudioPlayer, I assume you'll need to setup your AVAudioSession's category to honor the mute switch, but I have not tried it`.

Using Ambient mode for playing a video and PlayAndRecord mode for recording a video on camera screen, resolves the issue in our case.

The code in application:didFinishLaunchingWithOptions:

NSError *error = nil;
[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryAmbient error:&error];
[[AVAudioSession sharedInstance] setMode:AVAudioSessionModeVideoRecording error:&error];
[[AVAudioSession sharedInstance] setActive:YES error:&error];

The code in viewWillAppear on cameraController, if you have to use camera or recording in your app

[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayAndRecord error:nil];

The code in viewWillDisappear on cameraController

[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryAmbient error:nil];

Using these lines our Application records and plays a video and mute switch works perfectly under both iOS8 and iOS7!!!

>For Swift

Below framework works perfectly in device

https://github.com/akramhussein/Mute

Just install using pod or download from Git

pod 'Mute'

and use like below code

import UIKit
import Mute

class ViewController: UIViewController {

    @IBOutlet weak var label: UILabel! {
        didSet {
            self.label.text = ""
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()

        // Notify every 2 seconds
        Mute.shared.checkInterval = 2.0

        // Always notify on interval
        Mute.shared.alwaysNotify = true

        // Update label when notification received
        Mute.shared.notify = { m in
            self.label.text = m ? "Muted" : "Not Muted"
        }

        // Stop after 5 seconds
        DispatchQueue.main.asyncAfter(deadline: .now() + 5.0) {
            Mute.shared.isPaused = true
        }

        // Re-start after 10 seconds
        DispatchQueue.main.asyncAfter(deadline: .now() + 10.0) {
            Mute.shared.isPaused = false
        }
    }

}

Olie,

I believe you can find the answer to your question here:

https://devforums.apple.com/message/1135#1135

I'm assuming you have access to the Developer Forums at Apple.com :)