除iPhone 4以外，所有iOS设备上的音量都很好。在iPhone上，音量非常低

Question

I am developing an iOS app that runs on all iOS devices. In my app, I am playing some video files. Everything works fine on all devices except for iPhone 4. On iPhone4, volume level is very low even though all other apps work with normal volume level on that device. On all other devices, volume level is fine. Can anybody please help me with this trouble? Thanks in advance.

Here is the source code

NSInteger selectedVideoTag = sender.tag;
NSString *videoPath = [self getVideoToBePlayedForButtonTag:selectedVideoTag];
NSURL *videoUrl = [[NSURL alloc] initFileURLWithPath:videoPath];
NSLog(@"videoUrl = %@", videoUrl);
self.theMovie = [[MPMoviePlayerController alloc] initWithContentURL:videoUrl];

[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(moviePlaybackComplete:)
                                                 name:MPMoviePlayerPlaybackDidFinishNotification
                                           object:self.theMovie];
[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(moviePlaybackStateChaned:)
                                             name:MPMoviePlayerWillExitFullscreenNotification
                                           object:self.theMovie];


[self.theMovie prepareToPlay];
[self.theMovie.view setFrame:[[UIScreen mainScreen] bounds]];


[self.view addSubview:self.theMovie.view];
self.theMovie.controlStyle = MPMovieControlStyleDefault;
[self.theMovie setFullscreen:YES animated:YES];
[self.theMovie setScalingMode:MPMovieScalingModeAspectFill];
self.theMovie.movieSourceType = MPMovieSourceTypeFile;

[self.theMovie play];

Here is the code for getVideoToBePlayedForButtonTag message:

- (NSString *) getVideoToBePlayedForButtonTag:(NSInteger)btnTag
{
NSString *videoPath = nil;

//Trigger MixPanel events for selected button
Mixpanel *mixPanel = [Mixpanel sharedInstance];

switch (btnTag) {
    case 1:
        videoPath =[[NSBundle mainBundle] pathForResource:@"song_01" ofType:@"mp4"];
        break;
    case 2:
        videoPath =[[NSBundle mainBundle] pathForResource:@"song_02" ofType:@"mp4"];
        break;
    case 3:
        videoPath =[[NSBundle mainBundle] pathForResource:@"song_03" ofType:@"mp4"];
        break;
    case 4:
        videoPath =[[NSBundle mainBundle] pathForResource:@"song_04" ofType:@"mp4"];
        break;
    default:
        break;
}
return videoPath;

}

Answer 1

Found the solution for this problem. In my app, I had to override the mute switch, so I added the code in AppDelegate.m

NSError *categoryError = nil;
[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayAndRecord error:&categoryError];

Due to this category, iPhone 4 volume output was low. I changed the code to

[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:&categoryError];

Now, it works fine. Though, I still can't understand why was the sound output low only on iPhone 4 and not any other device like iPad, iPhone 5.