ios - 如何在不使用相机的情况下捕获不断变化的 CIImage 视频？

Question

我已经在这里提出了一个问题但没有任何回复: How do I record changes on a CIImage to a video using AVAssetWriter?

但也许我的问题需要更简单。我的谷歌搜索毫无结果。 如何在不使用相机的情况下实时捕获不断变化的 CIImage 视频？

使用 captureOutput，我得到一个 CMSampleBuffer，我可以将其制作成 CVPixelBuffer。 AVAssetWriterInput 的 mediaType 设置为视频，但我认为它需要压缩视频。此外，我不清楚 AVAssetWriterInput ExpectsMediaDataInRealTime 属性是否应设置为 true 。

看起来应该相当简单，但我尝试的所有操作都会使我的 AVAssetWriter 状态失败。

这是我最后一次尝试完成这项工作。仍然失败:

@objc func importLivePreview(){

    guard var importedImage = importedDryCIImage else { return }

    DispatchQueue.main.async(){

        // apply filter to camera image
        // this is what makes the CIImage appear that it is changing
        importedImage = self.applyFilterAndReturnImage(ciImage: importedImage, orientation: UIImage.Orientation.right, currentCameraRes:currentCameraRes!)


        if self.videoIsRecording &&
           self.assetWriterPixelBufferInput?.assetWriterInput.isReadyForMoreMediaData == true {

            guard let writer: AVAssetWriter = self.assetWriter, writer.status == .writing else {
                return
            }                       

            guard let cv:CVPixelBuffer = self.buffer(from: importedImage) else {
                print("CVPixelBuffer could not be created.")
                return
            }

            self.MTLContext?.render(_:importedImage, to:cv)

            self.currentSampleTime = CMTimeMakeWithSeconds(0.1, preferredTimescale: 1000000000)

            guard let currentSampleTime = self.currentSampleTime else {
                return
            }

            let success = self.assetWriterPixelBufferInput?.append(cv, withPresentationTime: currentSampleTime)

            if success == false {
                print("Pixel Buffer input failed")
            }

        }

        guard let MTLView = self.MTLCaptureView else {
            print("MTLCaptureView is not found or nil.")
            return
        }

        // update the MTKView with the changed CIImage so the user can see the changed image
        MTLView.image = importedImage


    }           

}

Answer 1

我成功了。问题是我没有抵消 currentSampleTime。这个例子没有准确的偏移量，但它表明它需要添加到最后一次。

@objc func importLivePreview(){

    guard var importedImage = importedDryCIImage else { return }

    DispatchQueue.main.async(){

        // apply filter to camera image
        // this is what makes the CIImage appear that it is changing
        importedImage = self.applyFilterAndReturnImage(ciImage: importedImage, orientation: UIImage.Orientation.right, currentCameraRes:currentCameraRes!)


        if self.videoIsRecording &&
           self.assetWriterPixelBufferInput?.assetWriterInput.isReadyForMoreMediaData == true {

            guard let writer: AVAssetWriter = self.assetWriter, writer.status == .writing else {
                return
            }                       

            guard let cv:CVPixelBuffer = self.buffer(from: importedImage) else {
                print("CVPixelBuffer could not be created.")
                return
            }

            self.MTLContext?.render(_:importedImage, to:cv)

            guard let currentSampleTime = self.currentSampleTime else {
                return
            }

            // offset currentSampleTime
            let sampleTimeOffset = CMTimeMakeWithSeconds(0.1, preferredTimescale: 1000000000)

            self.currentSampleTime = CMTimeAdd(currentSampleTime, sampleTimeOffset)

            print("currentSampleTime = \(String(describing: currentSampleTime))")

            let success = self.assetWriterPixelBufferInput?.append(cv, withPresentationTime: currentSampleTime)

            if success == false {
                print("Pixel Buffer input failed")
            }

        }

        guard let MTLView = self.MTLCaptureView else {
            print("MTLCaptureView is not found or nil.")
            return
        }

        // update the MTKView with the changed CIImage so the user can see the changed image
        MTLView.image = importedImage


    }           

}