捕获音频/视频后无法播放系统声音

Posted 2023-02-25

【中文标题】捕获音频/视频后无法播放系统声音

【英文标题】：Can't play system sounds after capturing audio / video

【发布时间】：2011-12-15 16:36:29

【问题描述】：

我正在使用 AVfoudnation 重新编码音频/视频。在开始捕获视频/音频之前，我需要使用系统声音播放声音。这是第一次正常工作，但是当我第二次尝试这样做时，系统 audi 没有播放。我的猜测是 AVfoundation 中的某些内容未正确发布。

在我的应用程序删除中，我在 applicationDidFinishLaunching 方法中有以下代码：

VKRSAppSoundPlayer *aPlayer = [[VKRSAppSoundPlayer alloc] init];
[aPlayer addSoundWithFilename:@"sound1" andExtension:@"caf"];
self.appSoundPlayer = aPlayer;
[aPlayer release];

还有这个方法

- (void)playSound:(NSString *)sound

    [appSoundPlayer playSound:sound];

如您所见，我正在使用 VKRSAppSoundPlayer，效果很好！

在一个视图中，我有这个代码：

- (void) startSession

    self.session = [[AVCaptureSession  alloc] init];

    [session beginConfiguration];
    if([session canSetSessionPreset:AVCaptureSessionPreset640x480])
        session.sessionPreset =  AVCaptureSessionPresetMedium; 

    [session commitConfiguration];


    CALayer *viewLayer = [videoPreviewView layer];

    AVCaptureVideoPreviewLayer *captureVideoPreviewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:session];

    captureVideoPreviewLayer.frame = viewLayer.bounds;

    [viewLayer addSublayer:captureVideoPreviewLayer];

    self.videoInput = [AVCaptureDeviceInput deviceInputWithDevice:[self frontFacingCameraIfAvailable] error:nil];
    self.audioInput = [AVCaptureDeviceInput deviceInputWithDevice:[self audioDevice] error:nil];

    if(videoInput)
        self.videoOutput = [[AVCaptureMovieFileOutput alloc] init];

        [session addOutput:videoOutput];
        //[videoOutput release];

        if([session canAddInput:videoInput])
            //[session beginConfiguration];
            [session addInput:videoInput];

        
        //[videoInput release];

        [session removeInput:[self audioInput]];
        if([session canAddInput:audioInput])
            [session addInput:audioInput];
        
        //[audioInput release];


        if([session canAddInput:audioInput])
            [session addInput:audioInput];


        NSLog(@"startRunning!");
        [session startRunning];  

        [self startRecording];


        if(![self recordsVideo])
            [self showAlertWithTitle:@"Video Recording Unavailable" msg:@"This device can't record video."];

    


- (void) stopSession

    [session stopRunning];
    [session release];   



- (AVCaptureDevice *)frontFacingCameraIfAvailable

    NSArray *videoDevices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeVideo];
    AVCaptureDevice *captureDevice = nil;

    Boolean cameraFound = false;

    for (AVCaptureDevice *device in videoDevices)
    
        NSLog(@"1 frontFacingCameraIfAvailable %d", device.position);
        if (device.position == AVCaptureDevicePositionBack)
            NSLog(@"1 frontFacingCameraIfAvailable FOUND");

            captureDevice = device;
            cameraFound = true;
            break;
        
    

    if(cameraFound == false)
        for (AVCaptureDevice *device in videoDevices)
        
            NSLog(@"2 frontFacingCameraIfAvailable %d", device.position);
            if (device.position == AVCaptureDevicePositionFront)
                NSLog(@"2 frontFacingCameraIfAvailable FOUND");

                captureDevice = device;
                break;
            
        
    

    return captureDevice;


- (AVCaptureDevice *) audioDevice

    NSArray *devices = [AVCaptureDevice devicesWithMediaType:AVMediaTypeAudio];
    if ([devices count] > 0) 
        return [devices objectAtIndex:0];
    
    return nil;


- (void) startRecording

#if _Multitasking_
    if ([[UIDevice currentDevice] isMultitaskingSupported]) 
        [self setBackgroundRecordingID:[[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^]];
    
#endif

    [videoOutput startRecordingToOutputFileURL:[self generatenewVideoPath] 
                             recordingDelegate:self];


- (void) stopRecording

    [videoOutput stopRecording];



- (void)captureOutput:(AVCaptureFileOutput *)captureOutput 
didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL 
      fromConnections:(NSArray *)connections error:(NSError *)error

    NSFileManager *man = [[NSFileManager alloc] init];
    NSDictionary *attrs = [man attributesOfItemAtPath: [outputFileURL path] error: NULL];
    NSString *fileSize = [NSString stringWithFormat:@"%llu", [attrs fileSize]];


    // close this screen
    [self exitScreen];


-(BOOL)recordsVideo

    AVCaptureConnection *videoConnection = [AVCamUtilities connectionWithMediaType:AVMediaTypeVideo 
                                                                   fromConnections:[videoOutput connections]];
    return [videoConnection isActive];


-(BOOL)recordsAudio

    AVCaptureConnection *audioConnection = [AVCamUtilities connectionWithMediaType:AVMediaTypeAudio 
                                                                   fromConnections:[videoOutput connections]];
    return [audioConnection isActive];

如果我这样做 [videoInput release];和[音频输入释放]；我遇到了错误的访问错误。这就是他们被注释掉的原因。这可能是问题的一部分。

如果我尝试播放系统声音n次，它可以工作，但如果我先进入录音脚本，然后它就不会工作了。

有什么想法吗？

【问题讨论】：

您需要更好地理解 self.iVar 的含义，以及 release 的含义。 release 减少保留计数，如果为 0，则使对象有资格进行释放。使用 self.iVar（假设您已将其声明为属性）会保留该 iVar，因此您可以在此之后立即释放它。但我认为这不是您的音频问题。

【参考方案1】：

释放 AVCaptureSession 的正确方法如下：

- (void) destroySession 

    // Notify the view that the session will end
    if ([delegate respondsToSelector:@selector(captureManagerSessionWillEnd:)]) 
        [delegate captureManagerSessionWillEnd:self];
    

    // remove the device inputs
    [session removeInput:[self videoInput]];
    [session removeInput:[self audioInput]];

    // release
    [session release];

    // remove AVCamRecorder
    [recorder release];

    // Notify the view that the session has ended
    if ([delegate respondsToSelector:@selector(captureManagerSessionEnded:)]) 
        [delegate captureManagerSessionEnded:self];
    

如果您遇到某种发布问题（访问权限不正确），我建议您将代码从当前“混乱”项目中移到其他新项目中，并在那里调试问题。

当我遇到类似问题时，我就这样做了。我在 Github 上分享了它，你可能会发现这个项目很有用：AVCam-CameraReleaseTest