Change iPhone application volume without volume changed box appearing (app for Japan)

I am making an Augmented Reality application that has picture taking functionality. It uses a custom function of mine to create a UIImage to save the screen. By law in Japan, cameras must have a shutter noise, which is why the iPhone camera always plays it. So far I have found a way to play sounds even when the iPhone is muted but it still relies on the user set volume. So I found a way using MPMusicPlayerController to control the application volume. This works, but when the volume is changed a box pops up signaling that the volume was changed.

Here is my code to play sounds even when m开发者_运维百科uted:

    AudioSessionInitialize (NULL, NULL, NULL, NULL);
AudioSessionSetActive(true);

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

I use the library Finch to play the sound (a light wrapper for openAL) and then MPMusicPlayerController to adjust the volume before play.

appMusicPlayer = [MPMusicPlayerController applicationMusicPlayer];
[appMusicPlayer setVolume:0.5f];

Anyone have experience with this or have made apps like this for Japan? I'm really at a loss. Thanks.

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The MPVolumeView will, while visible, block the floating box, even if the user can't actually see it.

Some sample code…

// create/synthesize ivars for "MPVolumeView" and "UIView" (both are necessary)
// I called them "mpVolumeView" and "mpVolumeViewParentView" respectively

// the UIView containing the MPVolumeView can have a frame of (0,0,1,1)
// this way, the user never sees the slider, but it still works normally

- (void)viewDidLoad {
    ...
    // with this, only the slider is visible
    mpVolumeViewParentView.backgroundColor = [UIColor clearColor];

    // initialize the volume slider (link the parent view in IB, or init here)
    mpVolumeView = [[MPVolumeView alloc] initWithFrame:
                                                mpVolumeViewParentView.bounds];

    // since it's a programmatic init, the subview must be added like so
    [mpVolumeViewParentView addSubview:mpVolumeView];

    // allows the floating box to appear without destroying mpVolumeView
    mpVolumeView.hidden = YES; // or [mpVolume setHidden:YES]; if you prefer
    ...
}

Before changing volume to force the camera to make sound…

mpVolumeView.hidden = NO; // view visible, box doesn't appear

And after sounds, so it doesn't look like you messed with anything…

mpVolumeView.hidden = YES; // view hidden, box appears

It might take some tweaking to get what you want, but it should be a good starting point.

This code is for iOS 5.1
I don't know what the compatibility is with older versions.