Avfoundation-同时播放、录制视频（包括音频和预览）

Question

我正在尝试同时录制和播放视频。使用AVFoundation是否可能？目前，只要我不录制音频，我就能做到这一点。一旦我将音频输入添加到AVCaptureSession并重新启动整个过程，我就会收到“AVCaptureSessionWasInterruptedNotification”而且录制停止。

以下是我的视频播放方式。

MPMoviePlayerController *moviePlayer = [[MPMoviePlayerController alloc]     initWithContentURL:[NSURL fileURLWithPath:path]];
[moviePlayer.view setFrame:self.playerView.bounds];
moviePlayer.useApplicationAudioSession=NO;
self.player = moviePlayer;

[moviePlayer release];

[self.playerView addSubview:player.view];

[player play];

这是我录制视频的方法：

NSError *error;

AVCamCaptureManager *captureManager = [[AVCamCaptureManager alloc] init];



if ([captureManager setupSessionWithPreset:AVCaptureSessionPresetLow error:&error])
{
    [self setCaptureManager:captureManager];



     AVCaptureVideoPreviewLayer *previewLayer = [[AVCaptureVideoPreviewLayer alloc] initWithSession:[captureManager session]];
     self.captureVideoPreviewLayer= previewLayer;

     UIView *view = [self cameraView];
     CALayer *viewLayer = [view layer];
     [viewLayer setMasksToBounds:YES];

     CGRect bounds = [view bounds];


     [captureVideoPreviewLayer setFrame:bounds];

     if ([captureVideoPreviewLayer isOrientationSupported]) 
     [captureVideoPreviewLayer setOrientation:AVCaptureVideoOrientationPortrait];


     [captureVideoPreviewLayer setVideoGravity:AVLayerVideoGravityResizeAspectFill];


   [[captureManager session] startRunning];

    [self setCaptureVideoPreviewLayer:captureVideoPreviewLayer];

    if ([[captureManager session] isRunning])
    {
        [captureManager setOrientation:AVCaptureVideoOrientationPortrait];
        [captureManager setDelegate:self];


        [viewLayer insertSublayer:captureVideoPreviewLayer below:[[viewLayer sublayers] objectAtIndex:0]];

        NSString *countString = [[NSString alloc] initWithFormat:@"%d", [[AVCaptureDevice devices] count]];
        NSLog(@"Device count: %@",countString);


    } else {
        UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Failure"
                                                            message:@"Failed to start session."
                                                           delegate:nil
                                                  cancelButtonTitle:@"Okay"
                                                  otherButtonTitles:nil];
        [alertView show];
        [alertView release];

    }
} else {
    UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Input Device Init Failed"
                                                        message:[error localizedDescription]
                                                       delegate:nil
                                              cancelButtonTitle:@"Okay"
                                              otherButtonTitles:nil];
    [alertView show];
    [alertView release];        
}

[captureManager release];
if (![[self captureManager] isRecording]) {
    [[self captureManager] startRecording];
} 

我使用苹果AVCam示例代码中的"AVCamCaptureManager"。

- i.jameelkhan

Answer 1

首先，将moviePlayer设置为使用应用程序音频会话：

moviePlayer.useApplicationAudioSession=YES;

在调用[[captureManager session] startRunning]之前，需要激活一个音频会话，并将其类别设置为“播放和录制”，并覆盖其属性以允许与其他会话混合。

// Set audio session category to "play and record"
NSError* error = nil;
AVAudioSession* audioSession = [AVAudioSession sharedInstance];
if (![audioSession setCategory:AVAudioSessionCategoryPlayAndRecord error:&error]) {
    NSLog(@"AVAudioSession setCategory failed: %@", [error 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
error = nil;
if (![audioSession setActive:YES error:&error]) {
    NSLog(@"AVAudioSession setActive:YES failed: %@", [error localizedDescription]);
}

- Francois Lambert

---

这很有趣，因为它与此处的接受答案相矛盾：https://dev59.com/KmPVa4cB1Zd3GeqP6YbM#10559420，该答案建议在捕获会话之后开始音频会话。 - qix

实际上，文档对useApplicationAudioSession有这样的说明：“一个布尔值，指示电影播放器是否应该使用应用程序的音频会话。（在iOS 6.0中已弃用。此属性没有替代项，并且不鼓励使用它。）”默认值已经是YES。 - qix

Answer 2

如果有其他人也在想...我成功地使用了Wertesse提出的方法，但它也适用于AVPlayer（它没有useApplicationAudioSession属性）。

- Bernie Habermeier

---

嘿Bernt，你有什么额外的见解可以让这个工作起来吗？我在我的viewDidLoad函数中有效地复制了原始问题中的代码，并添加了AudioSession配置。然而，我的CaptureSession仍然被停止了。如果能提供代码示例将不胜感激。谢谢！ - kungfoo