我是swift的新手，并尝试构建一个可以应用实时过滤器的相机应用程序，并使用应用的过滤器进行保存。
到目前为止，我可以使用应用的滤镜实时预览，但是当我将视频保存为全黑时。
import UIKit
import AVFoundation
import AssetsLibrary
import CoreMedia
import Photos
class ViewController: UIViewController , AVCaptureVideoDataOutputSampleBufferDelegate {
var captureSession: AVCaptureSession!
@IBOutlet weak var previewView: UIView!
@IBOutlet weak var recordButtton: UIButton!
@IBOutlet weak var imageView: UIImageView!
var assetWriter: AVAssetWriter?
var assetWriterPixelBufferInput: AVAssetWriterInputPixelBufferAdaptor?
var isWriting = false
var currentSampleTime: CMTime?
var currentVideoDimensions: CMVideoDimensions?
override func viewDidLoad() {
super.viewDidLoad()
FilterVendor.register()
setupCaptureSession()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
func setupCaptureSession() {
let captureSession = AVCaptureSession()
captureSession.sessionPreset = AVCaptureSessionPresetPhoto
guard let captureDevice = AVCaptureDevice.defaultDevice(withMediaType: AVMediaTypeVideo), let input = try? AVCaptureDeviceInput(device: captureDevice) else {
print("Can't access the camera")
return
}
if captureSession.canAddInput(input) {
captureSession.addInput(input)
}
let videoOutput = AVCaptureVideoDataOutput()
videoOutput.setSampleBufferDelegate(self, queue: DispatchQueue.main)
if captureSession.canAddOutput(videoOutput) {
captureSession.addOutput(videoOutput)
}
let previewLayer = AVCaptureVideoPreviewLayer(session: captureSession)
if((previewLayer) != nil) {
view.layer.addSublayer(previewLayer!)
}
captureSession.startRunning()
}
@IBAction func record(_ sender: Any) {
if isWriting {
print("stop record")
self.isWriting = false
assetWriterPixelBufferInput = nil
assetWriter?.finishWriting(completionHandler: {[unowned self] () -> Void in
self.saveMovieToCameraRoll()
})
} else {
print("start record")
createWriter()
assetWriter?.startWriting()
assetWriter?.startSession(atSourceTime: currentSampleTime!)
isWriting = true
}
}
func saveMovieToCameraRoll() {
PHPhotoLibrary.shared().performChanges({
PHAssetChangeRequest.creationRequestForAssetFromVideo(atFileURL: self.movieURL() as URL)
}) { saved, error in
if saved {
print("saved")
}
}
}
func movieURL() -> NSURL {
let tempDir = NSTemporaryDirectory()
let url = NSURL(fileURLWithPath: tempDir).appendingPathComponent("tmpMov.mov")
return url! as NSURL
}
func checkForAndDeleteFile() {
let fm = FileManager.default
let url = movieURL()
let exist = fm.fileExists(atPath: url.path!)
if exist {
do {
try fm.removeItem(at: url as URL)
} catch let error as NSError {
print(error.localizedDescription)
}
}
}
func createWriter() {
self.checkForAndDeleteFile()
do {
assetWriter = try AVAssetWriter(outputURL: movieURL() as URL, fileType: AVFileTypeQuickTimeMovie)
} catch let error as NSError {
print(error.localizedDescription)
return
}
let outputSettings = [
AVVideoCodecKey : AVVideoCodecH264,
AVVideoWidthKey : Int(currentVideoDimensions!.width),
AVVideoHeightKey : Int(currentVideoDimensions!.height)
] as [String : Any]
let assetWriterVideoInput = AVAssetWriterInput(mediaType: AVMediaTypeVideo, outputSettings: outputSettings as? [String : AnyObject])
assetWriterVideoInput.expectsMediaDataInRealTime = true
assetWriterVideoInput.transform = CGAffineTransform(rotationAngle: CGFloat(M_PI / 2.0))
let sourcePixelBufferAttributesDictionary = [
String(kCVPixelBufferPixelFormatTypeKey) : Int(kCVPixelFormatType_32BGRA),
String(kCVPixelBufferWidthKey) : Int(currentVideoDimensions!.width),
String(kCVPixelBufferHeightKey) : Int(currentVideoDimensions!.height),
String(kCVPixelFormatOpenGLESCompatibility) : kCFBooleanTrue
] as [String : Any]
assetWriterPixelBufferInput = AVAssetWriterInputPixelBufferAdaptor(assetWriterInput: assetWriterVideoInput,
sourcePixelBufferAttributes: sourcePixelBufferAttributesDictionary)
if assetWriter!.canAdd(assetWriterVideoInput) {
assetWriter!.add(assetWriterVideoInput)
} else {
print("no way\(assetWriterVideoInput)")
}
}
func captureOutput(_ captureOutput: AVCaptureOutput, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection) {
autoreleasepool {
connection.videoOrientation = AVCaptureVideoOrientation.landscapeLeft;
guard let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else { return }
let cameraImage = CIImage(cvPixelBuffer: pixelBuffer)
let filter = CIFilter(name: "Fİlter")!
filter.setValue(cameraImage, forKey: kCIInputImageKey)
let formatDescription = CMSampleBufferGetFormatDescription(sampleBuffer)!
self.currentVideoDimensions = CMVideoFormatDescriptionGetDimensions(formatDescription)
self.currentSampleTime = CMSampleBufferGetOutputPresentationTimeStamp(sampleBuffer)
if self.isWriting {
if self.assetWriterPixelBufferInput?.assetWriterInput.isReadyForMoreMediaData == true {
var newPixelBuffer: CVPixelBuffer? = nil
CVPixelBufferPoolCreatePixelBuffer(nil, self.assetWriterPixelBufferInput!.pixelBufferPool!, &newPixelBuffer)
let success = self.assetWriterPixelBufferInput?.append(newPixelBuffer!, withPresentationTime: self.currentSampleTime!)
if success == false {
print("Pixel Buffer failed")
}
}
}
DispatchQueue.main.async {
if let outputValue = filter.value(forKey: kCIOutputImageKey) as? CIImage {
let filteredImage = UIImage(ciImage: outputValue)
self.imageView.image = filteredImage
}
}
}
}
}
答案 0 :(得分：6)
我在下面的关键部分添加了一些评论：
func captureOutput(_ captureOutput: AVCaptureOutput, didOutputSampleBuffer sampleBuffer: CMSampleBuffer!, from connection: AVCaptureConnection) {
autoreleasepool {
connection.videoOrientation = AVCaptureVideoOrientation.landscapeLeft;
// COMMENT: This line makes sense - this is your pixelbuffer from the camera.
guard let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) else { return }
// COMMENT: OK, so you turn pixelBuffer into a CIImage...
let cameraImage = CIImage(cvPixelBuffer: pixelBuffer)
// COMMENT: And now you've create a CIImage with a Filter instruction...
let filter = CIFilter(name: "Fİlter")!
filter.setValue(cameraImage, forKey: kCIInputImageKey)
let formatDescription = CMSampleBufferGetFormatDescription(sampleBuffer)!
self.currentVideoDimensions = CMVideoFormatDescriptionGetDimensions(formatDescription)
self.currentSampleTime = CMSampleBufferGetOutputPresentationTimeStamp(sampleBuffer)
if self.isWriting {
if self.assetWriterPixelBufferInput?.assetWriterInput.isReadyForMoreMediaData == true {
// COMMENT: Here's where it gets weird. You've declared a new, empty pixelBuffer... but you already have one (pixelBuffer) that contains the image you want to write...
var newPixelBuffer: CVPixelBuffer? = nil
// COMMENT: And you grabbed memory from the pool.
CVPixelBufferPoolCreatePixelBuffer(nil, self.assetWriterPixelBufferInput!.pixelBufferPool!, &newPixelBuffer)
// COMMENT: And now you wrote an empty pixelBuffer back <-- this is what's causing the black frame.
let success = self.assetWriterPixelBufferInput?.append(newPixelBuffer!, withPresentationTime: self.currentSampleTime!)
if success == false {
print("Pixel Buffer failed")
}
}
}
// COMMENT: And now you're sending the filtered image back to the screen.
DispatchQueue.main.async {
if let outputValue = filter.value(forKey: kCIOutputImageKey) as? CIImage {
let filteredImage = UIImage(ciImage: outputValue)
self.imageView.image = filteredImage
}
}
}
}
在我看来，你基本上是在获取屏幕图像，创建一个过滤后的副本，然后创建一个空的像素缓冲区并将其写出来。
如果您编写的像素缓冲区而不是您正在创建的新像素，则应该成功写入图像。
成功写出已过滤视频所需的是从CIImage创建一个新的CVPixelBuffer - 这个解决方案已存在于StackOverflow上，我知道因为我自己需要这个步骤！