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我正在尝试构建一个简单的应用程序，从 MacBook 的内置 iSight 摄像头中捕获视频。我查看了开发人员网站上的几个示例项目，并在此处遵循教程：Apple's AVFoundation Guide。

每次我不断中断 AVCaptureMovieFileOutput 时，我都会收到一个未捕获的异常 - 没有活动/启用的连接。我是 AV 框架的新手，所以我不确定它为什么能识别 iSight，允许我将其输入到会话中，允许我为会话制作电影输出，但然后告诉我没有连接？它在寻找什么联系？（注意：我的视图控制器中还没有 QTMovieView，但我认为我只需要它来播放，而不是录制）。

我知道 iSight 可以正常工作，因为我最近在 Skype 上使用过它。

这是我的相关代码：

thisSession = [[AVCaptureSession alloc] init];

//set presets for this session
if ([thisSession canSetSessionPreset:AVCaptureSessionPreset640x480]) {

    thisSession.sessionPreset = AVCaptureSessionPreset640x480;
    NSLog(@"Session Preset: OK");

    //capture a device - captures all the devices, microphone, camera, etc.
    NSArray *devices = [AVCaptureDevice devices];

    //this will hold our decvice
    AVCaptureDevice* iSightCamera;

    for (AVCaptureDevice *device in devices) {

        //we only want to work with the internal camera
        if ([[device localizedName] isEqualToString:@"Built-in iSight"]) { 

            iSightCamera = device;

            //creating an input of the device for the session
            NSError *error = nil;
            AVCaptureDeviceInput* iSightCameraInput =
            [AVCaptureDeviceInput deviceInputWithDevice:iSightCamera error:&error];
            if (!iSightCameraInput) {
                NSLog(@"Error creating device input: %@", error);
            } else { 
                NSLog(@"iSight device input created!");

                //adding the device input to the session
                if ([thisSession canAddInput:iSightCameraInput]) {

                    [thisSession addInput:iSightCameraInput];
                    NSLog(@"iSight input added to session!");

                    //add the output to the session
                    AVCaptureMovieFileOutput *movieOutput = [[AVCaptureMovieFileOutput alloc] init];

                    if ([thisSession canAddOutput:movieOutput]) {

                        [thisSession beginConfiguration];
                        [thisSession addOutput:movieOutput];
                        [thisSession commitConfiguration];

                        NSLog(@"Movie output added to the session!");

                        //start writing the movie
                        NSURL *movieFolder = [NSURL fileURLWithPath:[@"~/Movies" stringByExpandingTildeInPath]];

                        [movieOutput startRecordingToOutputFileURL:movieFolder recordingDelegate:self];
                    }
                    else {
                        NSLog(@"Error: Could not add movie output to the session.");
                    }
                }
                else {
                    NSLog(@"Error: Could not add iSight to session.");
                }

            }

        }

    }
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