Due to the bug 17292753 mentioned here it is impossible to mute playback volume using device hardware buttons. The following methods are added since build 2.6.26 to mute
[[FPWCSApi2 getAudioManager] muteAudio];
and unmute audio playback
[[FPWCSApi2 getAudioManager] unmuteAudio];
It is necessary to subscribe to voluem change events to workarond the bug and allow to mute sound with hardware buttons (code)
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(volumeChanged:) name:@"AVSystemController_SystemVolumeDidChangeNotification" object:nil];
and mute audio when current volume value reaches the certain value, and unmute when this value is exceeded (code)
- (void)volumeChanged:(NSNotification *)notification
{
float volume =
[[[notification userInfo]
objectForKey:@"AVSystemController_AudioVolumeNotificationParameter"]
floatValue];
currentVolume = volume;
if (volume <= 0.0625) {
[[FPWCSApi2 getAudioManager] muteAudio];
} else {
[[FPWCSApi2 getAudioManager] unmuteAudio];
}
}