可以同时使用AVCaptureVideoDataOutput和AVCaptureMovieFileOutput吗？

Question

我想用我的代码同时录制视频和抓取帧。

我使用AVCaptureVideoDataOutput作为抓帧，使用AVCaptureMovieFileOutput作视频录制。但是在工作的同时却不能工作并得到错误代码-12780，而是个人。

我搜索了这个问题，但没有得到答案。有没有人有相同的经历或解释？ 这真的让我困扰了一会儿。

谢谢。

Answer 1

我不能回答的具体问题看跌，但使用我已经成功地录制视频，抓住在同一时间框架：

• AVCaptureSession和AVCaptureVideoDataOutput路由帧到我自己的代码
• AVAssetWriter，AVAssetWriterInput和AVAssetWriterInputPixelBufferAdaptor写入帧出来的H.264编码的电影文件

这还没有调查的音频。我最终从捕获会话获得CMSampleBuffers，然后将它们推入像素缓冲适配器。

编辑：所以我的代码看起来多少有点像，与您遇到任何问题与掠过，而忽略的范围问题位：

/* 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

这是汤米的回答迅速版。

// 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() 

虽然我并没有保证100％的准确性，因为我是新来的迅速。