Ios 如何在AVCaptureSession中为视频的每一帧应用过滤器？

我正在编写一个应用程序，它需要对使用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对每个视频帧进行过滤。 代码如下：

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!)
    ...
}

---

AVAssetWriterInput.append中的ret始终为false。我做错了什么？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。有可能将其安装到位吗？

我使用了几乎相同的代码来解决相同的问题。我发现为渲染创建的像素缓冲区有问题

append（sampleBuffer:）

始终返回false和

assetWriter。错误为

Error Domain=AVFoundationErrorDomain Code=-11800“操作可能会失败
未完成“UserInfo={NSUnderlyingError=0x17024ba30{Error
域=NSOSStatusErrorDomain代码=-12780“（空）”}，
NSLocalizedFailureReason=发生未知错误（-12780），
NSLocalizedDescription=操作无法完成}

他们说这是一个bug（如上所述），已经发布：

但出乎意料的是，当使用原始像素缓冲区进行渲染时，我发现这个问题消失了。见下面的代码：

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，我们都知道不允许修改示例缓冲区，但不知何故，这种方法会提供正常处理的视频。技巧是肮脏的，我不能说它在有预览层或一些并发处理例程的情况下是否合适。
你是否有可能修改
sampleBuffer
？我现在没有修改sampleBuffer。不过，如果我能，那就太好了。这样我就不用为过滤后的输出创建新的缓冲区了。上面说我们不能编辑它。用上面提到的方法看看有什么错误。