AVCaptureMovieFileOutput的意外行为

Question

我正在用AVCaptureMovieFIleOutput，制作一部银幕电影，但它显示出了意想不到的行为。

例如，如果我发送的是cropRect参数，捕获的电影是好的，但如果我制作的电影全屏幕，而不是电影文件，它是显示一个文件夹。我怎么才能摆脱它？

代码是:

    // Create a capture session
    mSession = [[AVCaptureSession alloc] init];

    // If you're on a multi-display system and you want to capture a secondary display,
    // you can call CGGetActiveDisplayList() to get the list of all active displays.
    // For this example, we just specify the main display.
    CGDirectDisplayID displayId = kCGDirectMainDisplay;

    // Create a ScreenInput with the display and add it to the session
    input = [[AVCaptureScreenInput alloc] initWithDisplayID:displayId];

    [input setCropRect:rect];

    if (!input) {
        mSession = nil;
        return;
    }
    if ([mSession canAddInput:input])
        [mSession addInput:input];

    // Create a MovieFileOutput and add it to the session
    mMovieFileOutput = [[AVCaptureMovieFileOutput alloc] init];
    if ([mSession canAddOutput:mMovieFileOutput])
        [mSession addOutput:mMovieFileOutput];

    // Start running the session
    [mSession startRunning];

    // Delete any existing movie file first
    if ([[NSFileManager defaultManager] fileExistsAtPath:[destPath path]])
    {
        NSError *err;
        if (![[NSFileManager defaultManager] removeItemAtPath:[destPath path] error:&err])
        {
            NSLog(@"Error deleting existing movie %@",[err localizedDescription]);
        }
    }

    // Start recording to the destination movie file
    // The destination path is assumed to end with ".mov", for example, @"/users/master/desktop/capture.mov"
    // Set the recording delegate to self
    [mMovieFileOutput startRecordingToOutputFileURL:destPath recordingDelegate:self];

Answer 1

必须使用setSessionPreset属性。

sessionPreset的默认值是AVCaptureSessionPresetHigh，它不适用于全屏截图。必须提供任何其他预置。