使用AVCaptureVideoDataOutput录制视频

Question

我不确定应该在方法中添加什么

- (void) captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection;

为了将帧写入视频。 任何人都可以与我分享这种方法的代码主体，这种方法的结果是将帧录制到电影中？

我以为我正确设置了assetWriter和videoInput，但是我得到的只是一部重复使用1帧的电影。

Answer 1

检查Apple示例代码Rosy Writer 。 这是您正在寻找的一个很好的例子。

Answer 2

您可以使用此方法同时成功录制视频和抓取帧：

AVCaptureSession *captureSession = [AVCaptureSession new];
AVCaptureDevice *captureDevice = [AVCaptureDevice new];
AVCaptureDeviceInput *deviceInput = [AVCaptureDeviceInput new];
AVCaptureVideoDataOutput *output = [AVCaptureVideoDataOutput new];


NSDictionary *outputSettings = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithInt:640], AVVideoWidthKey, [NSNumber numberWithInt:480], AVVideoHeightKey, AVVideoCodecH264, AVVideoCodecKey, nil];
AVAssetWriterInput *assetWriterInput = [AVAssetWriterInput  assetWriterInputWithMediaType:AVMediaTypeVideo outputSettings:outputSettings];


/ AVCaptureVideDataOutput /
AVAssetWriterInputPixelBufferAdaptor *pixelBufferAdaptor =
           [[AVAssetWriterInputPixelBufferAdaptor alloc] 
                initWithAssetWriterInput:assetWriterInput 
                sourcePixelBufferAttributes:
                     [NSDictionary dictionaryWithObjectsAndKeys:
                          [NSNumber numberWithInt:kCVPixelFormatType_32BGRA], 
                           kCVPixelBufferPixelFormatTypeKey,
                     nil]];


/* Asset writer with MPEG4 format*/
AVAssetWriter *assetWriterMyData = [[AVAssetWriter alloc]
                                initWithURL:URLFromSomwhere
                                fileType:AVFileTypeMPEG4
                                error:you need to check error conditions,
                                      this example is too lazy];
[assetWriterMyData addInput:assetWriterInput];
assetWriterInput.expectsMediaDataInRealTime = YES;

/ Start writing data /

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



- (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++;
}

/* To stop recording, stop capture session and finish writing data*/

[captureSession stopRunning];
[assetWriterMyData finishWriting];