Question

我有一个播放一些背景音乐的应用程序，当按下某个按钮时，它会使用导航控制器推送新视图。该新视图具有MPMoviePlayerController和带有共享AudioSession的AVCaptureSession。在该视图被解除之后，背景中的声音与其相比非常柔和。是什么导致音量在播放后如此低迷？

NSError* error4 = nil;
AVAudioSession* audioSession = [AVAudioSession sharedInstance];
if (![audioSession setCategory:AVAudioSessionCategoryPlayAndRecord error:&error4]) {
    NSLog(@"AVAudioSession setCategory failed: %@", [error4 localizedDescription]);
}

// Set audio session property "allow mixing" to true so audio can be recorded while it is playing
UInt32 allowMixing = true;
OSStatus status = AudioSessionSetProperty(kAudioSessionProperty_OverrideCategoryMixWithOthers, sizeof(allowMixing), &allowMixing);
if (status != kAudioSessionNoError) {
    NSLog(@"AudioSessionSetProperty(kAudioSessionProperty_OverrideCategoryMixWithOthers) failed: %ld", status);
}

// Activate the audio session
error4 = nil;
if (![audioSession setActive:YES error:&error4]) {
    NSLog(@"AVAudioSession setActive:YES failed: %@", [error4 localizedDescription]);
}
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectoryPath = [paths objectAtIndex:0];

NSString *proud = [[documentsDirectoryPath stringByAppendingPathComponent:@"imissyou"] stringByAppendingPathComponent:selectedCountry];

NSURL  *movieURL = [[NSURL fileURLWithPath:proud] retain];
player =

[[MPMoviePlayerController alloc] initWithContentURL: movieURL];
player.useApplicationAudioSession=YES;

[player prepareToPlay];
player.controlStyle = MPMovieControlStyleNone;
player.allowsAirPlay = NO;
player.scalingMode = MPMovieScalingModeFill;   

player.view.frame = self.view.frame;

[self.view insertSubview:player.view belowSubview:vImagePreview];

[player setFullscreen:YES animated:YES];

// ...

[[NSNotificationCenter defaultCenter] 
 addObserver:self
 selector:@selector(movieFinishedCallback:)
 name:MPMoviePlayerPlaybackDidFinishNotification
 object:player];

[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(exitedFullscreen:) name:MPMoviePlayerDidExitFullscreenNotification object:player];


[[NSNotificationCenter defaultCenter] addObserver:self
                                         selector:@selector(moviePlayerWillExitFullscreen:)
                                             name:MPMoviePlayerWillExitFullscreenNotification
                                           object:player];


[player play];


session = [[AVCaptureSession alloc] init];
[session beginConfiguration];
session.sessionPreset = AVCaptureSessionPresetMedium;

CALayer *viewLayer = self.vImagePreview.layer;
NSLog(@"viewLayer = %@", viewLayer);

AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];
captureVideoPreviewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill;
captureVideoPreviewLayer.frame = self.vImagePreview.bounds;
[captureVideoPreviewLayer setCornerRadius:14];
[captureVideoPreviewLayer setBorderWidth:3.0];
[captureVideoPreviewLayer setBorderColor:[[UIColor whiteColor] CGColor]];
[[vImagePreview layer] setCornerRadius:14];


[[vImagePreview layer] setBorderWidth:3.0];


[[vImagePreview layer] setBorderColor:[[UIColor whiteColor] CGColor]];

[self.vImagePreview.layer addSublayer:captureVideoPreviewLayer];
[captureVideoPreviewLayer release];
AVCaptureDevice *device = [self frontFacingCameraIfAvailable];
NSError *error = nil;
AVCaptureDeviceInput *input = [AVCaptureDeviceInput deviceInputWithDevice:device error:&error];
if (!input) {
    // Handle the error appropriately.
    NSLog(@"ERROR: trying to open camera: %@", error);
}

AVCaptureDevice *audioCaptureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeAudio];
NSError *error2 = nil;
AVCaptureDeviceInput *audioInput = [AVCaptureDeviceInput deviceInputWithDevice:audioCaptureDevice error:&error2];






AVCaptureMovieFileOutput *movieFileOutput = [[AVCaptureMovieFileOutput alloc] init];

NSString *archives = [documentsDirectoryPath stringByAppendingPathComponent:@"archives"];
NSString *editedfilename = [[selectedCountry lastPathComponent] stringByDeletingPathExtension];
NSString *datestring = [[editedfilename stringByAppendingString:@" "] stringByAppendingString:currentTime];
NSLog(@"%@", datestring);
NSString *outputpathofmovie = [[archives stringByAppendingPathComponent:datestring] stringByAppendingString:@".mp4"];
NSURL *outputURL = [[NSURL alloc] initFileURLWithPath:outputpathofmovie];
[session addInput:input];
[session addInput:audioInput];
[session addOutput:movieFileOutput];
[session commitConfiguration];
[session startRunning];
[movieFileOutput startRecordingToOutputFileURL:outputURL recordingDelegate:self];
[movieURL release];
[outputURL release];

Answer 1

音频会话可能会“躲避”背景音乐。您可能希望将属性“kAudioSessionProperty_OtherMixableAudioShouldDuck”设置为false以禁用该属性。

Answer 2

我现在明白了。我将类别设置为PlayAndRecord。我将其更改为Ambient（也允许在播放音频时录制音频）并删除OverrideCategoryMixWithOthers的属性，只留下

OSStatus propertySetError = 0; 
UInt32 allowMixing = true; 
propertySetError |= AudioSessionSetProperty(kAudioSessionProperty_OtherMixableAudioShouldDuck, sizeof(allowMixing), &allowMixing);

MPMoviePlayerController导致所有其他音频变软（MP完成后）

2 个答案: