Question

我正在编写一个应用程序，需要对使用AVCaptureSession捕获的视频应用过滤器。过滤后的输出将写入输出文件。我目前正在使用CIFilter和CIImage来过滤每个视频帧。这是代码：

func captureOutput(_ captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection!) {
    ...
    let pixelBuffer = CMSampleBufferGetImageBuffer(samples)!
    let options = [kCVPixelBufferPixelFormatTypeKey as String : kCVPixelFormatType_420YpCbCr8BiPlanarFullRange]
    let cameraImage = CIImage(cvImageBuffer: pixelBuffer, options: options)
    let filter = CIFilter(name: "CIGaussianBlur")!
    filter.setValue((70.0), forKey: kCIInputRadiusKey)
    filter.setValue(cameraImage, forKey: kCIInputImageKey)
    let result = filter.outputImage!
    var pixBuffer:CVPixelBuffer? = nil;
    let fmt = CVPixelBufferGetPixelFormatType(pixelBuffer)
    CVPixelBufferCreate(kCFAllocatorSystemDefault,
                        CVPixelBufferGetWidth(pixelBuffer),
                        CVPixelBufferGetHeight(pixelBuffer),
                        fmt,
                        CVBufferGetAttachments(pixelBuffer, .shouldPropagate),
                        &pixBuffer);

    CVBufferPropagateAttachments(pixelBuffer, pixBuffer!)
    let eaglContext = EAGLContext(api: EAGLRenderingAPI.openGLES3)!
    eaglContext.isMultiThreaded = true
    let contextOptions = [kCIContextWorkingColorSpace : NSNull(), kCIContextOutputColorSpace: NSNull()]
    let context = CIContext(eaglContext: eaglContext, options: contextOptions)
    CVPixelBufferLockBaseAddress( pixBuffer!, CVPixelBufferLockFlags(rawValue: 0))
    context.render(result, to: pixBuffer!)
    CVPixelBufferUnlockBaseAddress( pixBuffer!, CVPixelBufferLockFlags(rawValue: 0))
    var timeInfo = CMSampleTimingInfo(duration: sampleBuffer.duration,
                                      presentationTimeStamp: sampleBuffer.presentationTimeStamp,
                                      decodeTimeStamp: sampleBuffer.decodeTimeStamp)
    var sampleBuf:CMSampleBuffer? = nil;
    CMSampleBufferCreateReadyWithImageBuffer(kCFAllocatorDefault,
                                             pixBuffer!,
                                             samples.formatDescription!,
                                             &timeInfo,
                                             &sampleBuf)

    // write to video file
    let ret = assetWriterInput.append(sampleBuf!)
    ...
}

来自AVAssetWriterInput.append的ret始终为false。我在这做错了什么？而且，我使用的方法效率很低。在此过程中会创建一些临时副本。是否有可能就地？

Answer 1

我使用了几乎相同的代码并遇到了同样的问题。我发现创建用于渲染的像素缓冲区有问题。 append(sampleBuffer:)总是返回false，assetWriter.error是

错误域= AVFoundationErrorDomain代码= -11800＆＃34;操作可以没完成＆＃34; UserInfo = {NSUnderlyingError = 0x17024ba30 {错误 Domain = NSOSStatusErrorDomain Code = -12780＆＃34;（null）＆＃34;}， NSLocalizedFailureReason =发生未知错误（-12780）， NSLocalizedDescription =无法完成操作}

他们说这是一个错误（如here所述），已发布：https://bugreport.apple.com/web/?problemID=34574848。

但是我意外地发现当使用原始像素缓冲区进行渲染时问题会消失。请参阅以下代码：

let sourcePixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)!
let sourceImage = CIImage(cvImageBuffer: sourcePixelBuffer)
let filter = CIFilter(name: "CIGaussianBlur", withInputParameters: [kCIInputImageKey: sourceImage])!
let filteredImage = filter.outputImage!

var pixelBuffer: CVPixelBuffer? = nil
let width = CVPixelBufferGetWidth(sourcePixelBuffer)
let height = CVPixelBufferGetHeight(sourcePixelBuffer)
let pixelFormat = CVPixelBufferGetPixelFormatType(sourcePixelBuffer)
let attributes = CVBufferGetAttachments(sourcePixelBuffer, .shouldPropagate)!
CVPixelBufferCreate(nil, width, height, pixelFormat, attributes, &pixelBuffer)
CVBufferPropagateAttachments(sourcePixelBuffer, pixelBuffer!)

var filteredPixelBuffer = pixelBuffer!      // this never works
filteredPixelBuffer = sourcePixelBuffer     // 0_0

let context = CIContext(options: [kCIContextOutputColorSpace: CGColorSpace(name: CGColorSpace.sRGB)!])
context.render(filteredImage, to: filteredPixelBuffer)  // modifying original image buffer here!

let presentationTimestamp = CMSampleBufferGetPresentationTimeStamp(sampleBuffer)
var timing = CMSampleTimingInfo(duration: kCMTimeInvalid, presentationTimeStamp: presentationTimestamp, decodeTimeStamp: kCMTimeInvalid)

var processedSampleBuffer: CMSampleBuffer? = nil
var formatDescription: CMFormatDescription? = nil
CMVideoFormatDescriptionCreateForImageBuffer(nil, filteredPixelBuffer, &formatDescription)
CMSampleBufferCreateReadyWithImageBuffer(nil, filteredPixelBuffer, formatDescription!, &timing, &processedSampleBuffer)

print(assetInput!.append(processedSampleBuffer!))

当然，我们都知道你不允许修改样本缓冲区，但不知怎的，这种方法可以提供正常处理的视频。诡计很脏，我不能说如果你有预览图层或一些并发的处理程序就没问题。

如何在AVCaptureSession中为视频的每个帧应用滤镜？

1 个答案: