可以同時使用AVCaptureVideoDataOutput和AVCaptureMovieFileOutput嗎？

Question

我想用我的代碼同時錄製視頻和抓取幀。

我使用AVCaptureVideoDataOutput作爲抓幀，使用AVCaptureMovieFileOutput作視頻錄製。但是在工作的同時卻不能工作並得到錯誤代碼-12780，而是個人。

我搜索了這個問題，但沒有得到答案。有沒有人有相同的經歷或解釋？ 這真的讓我困擾了一會兒。

謝謝。

Answer 1

我不能回答的具體問題看跌，但使用我已經成功地錄製視頻，抓住在同一時間框架：

• AVCaptureSession和AVCaptureVideoDataOutput路由幀到我自己的代碼
• AVAssetWriter，AVAssetWriterInput和AVAssetWriterInputPixelBufferAdaptor寫入幀出來的H.264編碼的電影文件

這還沒有調查的音頻。我最終從捕獲會話獲得CMSampleBuffers，然後將它們推入像素緩衝適配器。

編輯：所以我的代碼看起來多少有點像，與您遇到任何問題與掠過，而忽略的範圍問題位：

/* to ensure I'm given incoming CMSampleBuffers */ 
AVCaptureSession *captureSession = alloc and init, set your preferred preset/etc; 
AVCaptureDevice *captureDevice = default for video, probably; 

AVCaptureDeviceInput *deviceInput = input with device as above, 
            and attach it to the session; 

AVCaptureVideoDataOutput *output = output for 32BGRA pixel format, with me as the 
            delegate and a suitable dispatch queue affixed. 

/* to prepare for output; I'll output 640x480 in H.264, via an asset writer */ 
NSDictionary *outputSettings = 
    [NSDictionary dictionaryWithObjectsAndKeys: 

      [NSNumber numberWithInt:640], AVVideoWidthKey, 
      [NSNumber numberWithInt:480], AVVideoHeightKey, 
      AVVideoCodecH264, AVVideoCodecKey, 

      nil]; 

AVAssetWriterInput *assetWriterInput = [AVAssetWriterInput 
            assetWriterInputWithMediaType:AVMediaTypeVideo 
                outputSettings:outputSettings]; 

/* I'm going to push pixel buffers to it, so will need a 
    AVAssetWriterPixelBufferAdaptor, to expect the same 32BGRA input as I've 
    asked the AVCaptureVideDataOutput to supply */ 
AVAssetWriterInputPixelBufferAdaptor *pixelBufferAdaptor = 
      [[AVAssetWriterInputPixelBufferAdaptor alloc] 
       initWithAssetWriterInput:assetWriterInput 
       sourcePixelBufferAttributes: 
        [NSDictionary dictionaryWithObjectsAndKeys: 
          [NSNumber numberWithInt:kCVPixelFormatType_32BGRA], 
          kCVPixelBufferPixelFormatTypeKey, 
        nil]]; 

/* that's going to go somewhere, I imagine you've got the URL for that sorted, 
    so create a suitable asset writer; we'll put our H.264 within the normal 
    MPEG4 container */ 
AVAssetWriter *assetWriter = [[AVAssetWriter alloc] 
           initWithURL:URLFromSomwhere 
           fileType:AVFileTypeMPEG4 
           error:you need to check error conditions, 
             this example is too lazy]; 
[assetWriter addInput:assetWriterInput]; 

/* we need to warn the input to expect real time data incoming, so that it tries 
    to avoid being unavailable at inopportune moments */ 
assetWriterInput.expectsMediaDataInRealTime = YES; 

... eventually ... 

[assetWriter startWriting]; 
[assetWriter startSessionAtSourceTime:kCMTimeZero]; 
[captureSession startRunning]; 

... elsewhere ... 

- (void)  captureOutput:(AVCaptureOutput *)captureOutput 
    didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer 
      fromConnection:(AVCaptureConnection *)connection 
{ 
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer); 

    // a very dense way to keep track of the time at which this frame 
    // occurs relative to the output stream, but it's just an example! 
    static int64_t frameNumber = 0; 
    if(assetWriterInput.readyForMoreMediaData) 
     [pixelBufferAdaptor appendPixelBuffer:imageBuffer 
         withPresentationTime:CMTimeMake(frameNumber, 25)]; 
    frameNumber++; 
} 

... and, to stop, ensuring the output file is finished properly ... 

[captureSession stopRunning]; 
[assetWriter finishWriting]; 

Answer 2

這是湯米的回答迅速版。

// Set up the Capture Session 
// Add the Inputs 
// Add the Outputs 


var outputSettings = [ 
    AVVideoWidthKey : Int(640), 
    AVVideoHeightKey : Int(480), 
    AVVideoCodecKey : .h264 
] 

    var assetWriterInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo,outputSettings: outputSettings) 

    var pixelBufferAdaptor = AVAssetWriterInputPixelBufferAdaptor(assetWriterInput, sourcePixelBufferAttributes: 
     [ kCVPixelBufferPixelFormatTypeKey : Int(kCVPixelFormatType_32BGRA)]) 


    var assetWriter = AVAssetWriter(url: URLFromSomwhere, fileType: AVFileTypeMPEG4 , error : Error) 
     assetWriter.addInput(assetWriterInput) 
     assetWriterInput.expectsMediaDataInRealTime = true 
     assetWriter.startWriting() 
     assetWriter.startSession(atSourceTime: kCMTimeZero) 

    captureSession.startRunning() 


    func captureOutput(_ captureOutput: AVCaptureOutput, didOutputSampleBuffer sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) { 

    var imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) 
    // a very dense way to keep track of the time at which this frame 
    // occurs relative to the output stream, but it's just an example! 
    var frameNumber: Int64 = 0 

      if assetWriterInput.readyForMoreMediaData { 
    pixelBufferAdaptor.appendPixelBuffer(imageBuffer, withPresentationTime: CMTimeMake(frameNumber, 25)) 
       } 
       frameNumber += 1 } 

     captureSession.stopRunning() 
     assetWriter.finishWriting() 

雖然我並沒有保證100％的準確性，因爲我是新來的迅速。