PlaySystemSound with mute switch on

问题

I know, I have to set the AudioSession to the 'playback' category, which allows audio even when the mute switch is on. This is what I do, but sound still gets muted when switch is on.

 UInt32 sessionCategory = kAudioSessionCategory_MediaPlayback;
 AudioSessionSetProperty(kAudioSessionProperty_AudioCategory,sizeof(sessionCategory), &sessionCategory);

 SystemSoundID soundID;
 NSString *path = [[NSBundle mainBundle] pathForResource:soundString ofType:@"wav"];    

 AudioServicesCreateSystemSoundID((CFURLRef)[NSURL fileURLWithPath:path],&soundID);
 AudioServicesPlaySystemSound (soundID);

EDIT: by the way, the app is a soundpad. Playing sound is the sole purpose of the app. Here's what Apple Doc says about this:

Use this category for an application whose audio playback is of primary importance. Your audio plays even with the screen locked and with the Ring/Silent switch set to silent.

EDIT 2: with the mute switch on, sound wont even play through the headphones. I know the user is king. I know the mute switch has its purpose. That is not the question. I'm trying to get an answer on the fact that setting the AudioSession category to kAudioSessionCategory_MediaPlayback doesn't have the expected result.

EDIT 3: following Jonathan Watmough's suggestion, I set the AudioServices kAudioServicesPropertyIsUISound property, but still no luck. Am I missing something?

// set the session property
UInt32 sessionCategory = kAudioSessionCategory_MediaPlayback;
AudioSessionSetProperty(kAudioSessionProperty_AudioCategory,sizeof(sessionCategory), &sessionCategory);

// creates soundID
SystemSoundID soundID;
NSString *path = [[NSBundle mainBundle] pathForResource:soundString ofType:@"wav"];    
AudioServicesCreateSystemSoundID((CFURLRef)[NSURL fileURLWithPath:path],&soundID);

// Jonathan Watmough suggestion
UInt32 flag = 0;
AudioServicesSetProperty(kAudioServicesPropertyIsUISound, sizeof(UInt32), &soundID, sizeof(UInt32), &flag);

AudioServicesPlaySystemSound (soundID);

回答1:

Well to add on Jonathan Watmough's answer, indeed it doesn't seem possible to let AudioServicesSystemSound overwrite the mute switch. What I ended up doing is using OpenAL to play the sounds, which will play just fine following the Audio Session category you specify. Here's how I setup the Audio session:

AudioSessionInitialize(NULL, NULL, NULL, NULL);
UInt32 sessionCategory = kAudioSessionCategory_MediaPlayback;
AudioSessionSetProperty(kAudioSessionProperty_AudioCategory,sizeof(sessionCategory), &sessionCategory);
AudioSessionSetActive(YES);

To play the sounds, I used Finch, a simple OpenAL-based sound effect player for iPhone.

回答2:

I haven't tried it yet, but you may want to change the property on your loaded sound:

kAudioServicesPropertyIsUISound A UInt32 value, where 1 means that, for the audio file specified by a system sound passed in the inSpecifier parameter, the System Sound server respects the user setting in the Sound Effects preference and is silent when the user turns off sound effects. This property is set to 1 by default. Set it to 0 for the system sound to always play when passed to AudioServicesPlaySystemSound, regardless of the user's setting in sound preferences. Available in iPhone OS 2.0 and later. Declared in AudioServices.h.

I'd expect that having done everything else right, setting the property to 0 will tell the system that your sound is an app sound, and not a 'UI' sound and hence subject to muting.

EDIT: It looks like it can't be done with system sounds. If you go through OpenAL, you will obviously be able to play with the mute button set.

I built the SysSound sample, and added the following code to set the flag as you did above, and it doesn't play on mute at all.

 // Set the sound to always play
    int setTo0 = 0;
    AudioServicesSetProperty( kAudioServicesPropertyIsUISound,0,nil,
                             4,&setTo0 );

回答3:

You are calling setActive:error: for the AVAudioSession somewhere right? Here is the code that I use to initialize. But I'm not using system sounds, I'm using AVAudioPlayer to play sounds.

avSession = [AVAudioSession sharedInstance];    // init session, important

// allow other audio to mix, such as iPod
const UInt32 categoryProp = kAudioSessionCategory_MediaPlayback;
AudioSessionSetProperty(kAudioSessionProperty_AudioCategory, sizeof(categoryProp), &categoryProp);

UInt32 category = kAudioSessionCategory_MediaPlayback;
AudioSessionSetProperty(kAudioSessionProperty_AudioCategory, sizeof(category), &category);

// Allow our audio to mix with any iPod audio that is playing
AudioSessionSetProperty (kAudioSessionProperty_OverrideCategoryMixWithOthers, sizeof(setProperty_YES), &setProperty_YES);

[avSession setActive:YES error:nil];

回答4:

I cannot find it explicitly mentioned in the docs, but I would expect the AudioServicesPlaySystemSound() ignores your audio session configuration.

If you want to control the session mixing and other properties you need to use AVAudioPlayer instead e.g.:

NSError *err;
AVAudioSession *session = [AVAudioSession sharedInstance];
[session setCategory:AVAudioSessionCategoryPlayback error:&err];
[session setActive:YES error:&err];

NSString *path = [[NSBundle mainBundle] pathForResource:@"Basso" ofType:@"aiff"];    
AVAudioPlayer *player = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL fileURLWithPath:path] error:&err];
[player prepareToPlay];
[player play];

回答5:

i am using the below code to solve my issue

AudioSessionInitialize(NULL, NULL, NULL, NULL); UInt32   
sessionCategory = kAudioSessionCategory_MediaPlayback;    
AudioSessionSetProperty(kAudioSessionProperty_AudioCategory,sizeof(sessionCategory),
&sessionCategory); AudioSessionSetActive(YES);

来源：https://stackoverflow.com/questions/3058507/playsystemsound-with-mute-switch-on

标签

iphone

audio

audiosession