使用 AVFoundation 框架 iPhone 录制视频?

问题描述

我正在借助 WWDC 2010 AVCamDemo 示例.在应用程序中，我需要从 iPhone 的前置摄像头录制视频，但由于我所在的地方没有新的 iPhone 4，我无法正确测试代码.

I'm developing an application with the help of sample code from the WWDC 2010 AVCamDemo example. In the app I need to record a video from the front camera of iPhone, but since the new iPhone 4 is not available at my place I am not able to test the code properly.

如果有人能提醒我我的方向是否正确，我将非常感激.当我设置 AVCaptureSession 时，我可以在 iPhone 3G(升级到 iOS 4.1)上测试的有限代码崩溃，如下面的代码所示:

I would be really thankful if someone can give me a heads up whether I'm going in the right direction or not. The limited code I could test on my iPhone 3G (upgraded to iOS 4.1) crashes when I set the AVCaptureSession, as shown in the code below:

- (void)recordVideo
{
    NSLog(@"video recording on");

    AVCaptureDevice *videoCaptureDevice = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo];
    AVCaptureDeviceInput *videoInput = [[AVCaptureDeviceInput alloc] initWithDevice:videoCaptureDevice error:nil];  
    AVCaptureMovieFileOutput *movieFileOutput = [[AVCaptureMovieFileOutput alloc] init];

    [movieFileOutput release];

    AVCaptureSession *session = [[AVCaptureSession alloc] init];
    [session addInput:videoInput];
    [session addOutput:movieFileOutput];
    [self setSession:session]; // crashes

    if (![session isRunning])
    {
        [self performSelector:@selector(startRecording) withObject:nil afterDelay:1.0];
        [session startRunning];
    }
}


- (void)startRecording
{

    AVCaptureConnection *videoConnection = [playVideo connectionWithMediaType:AVMediaTypeVideo fromConnections:[[self movieFileOutput] connections]];

    if ([videoConnection isVideoOrientationSupported]) {
        [videoConnection setVideoOrientation:[self orientation]]; 
    }

    [[self movieFileOutput] startRecordingToOutputFileURL:[self tempFileURL]
                                        recordingDelegate:self];
}


- (void) stopRecording
{
    NSLog(@"stop recording");
    [[self movieFileOutput] stopRecording];
}

- (NSURL *) tempFileURL
{

    NSString *outputPath = [[NSString alloc] initWithFormat:@"%@%@", NSTemporaryDirectory(), @"output.mov"];
    NSURL *outputURL = [[NSURL alloc] initFileURLWithPath:outputPath];
    NSFileManager *fileManager = [NSFileManager defaultManager];
    if ([fileManager fileExistsAtPath:outputPath]) {
        NSLog(@"file saved");
    }
    [outputPath release];
    return [outputURL autorelease];
}

+ (AVCaptureConnection *)connectionWithMediaType:(NSString *)mediaType fromConnections:(NSArray *)connections;
{
    for ( AVCaptureConnection *connection in connections ) {
        for ( AVCaptureInputPort *port in [connection inputPorts] ) {
            if ( [[port mediaType] isEqual:mediaType] ) {
                return [[connection retain] autorelease];
            }
        }
    }
    return nil;
}

- (void)captureOutput:(AVCaptureFileOutput *)captureOutput
didStartRecordingToOutputFileAtURL:(NSURL *)fileURL
                   fromConnections:(NSArray *)connections
{

}

- (void)captureOutput:(AVCaptureFileOutput *)captureOutput
didFinishRecordingToOutputFileAtURL:(NSURL *)outputFileURL
                    fromConnections:(NSArray *)connections
                              error:(NSError *)error
{
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];

    if ([library videoAtPathIsCompatibleWithSavedPhotosAlbum:outputFileURL])
    {
        [library writeVideoAtPathToSavedPhotosAlbum:outputFileURL
                                    completionBlock:^(NSURL *assetURL, NSError *error)];
    }

    [library release];       
}

推荐答案

movieFileOutput 分配后立即释放.(第 9 行)

movieFileOutput is released immediately after it has been allocated. (line 9)

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