Ios 无法使用AVAssetTrackReaderOutput在while循环中更新UIViewImage
我试图从视频中提取每一帧,进行一些图像处理,然后将图像显示回UIImageView 如果我手动单击UIButton,图像将显示并迭代整个视频,并显示每个帧 但是,如果我将更新显示嵌入while循环,则视图不会更新(即,在设备上它不会更新) 我认为这是因为相对于在屏幕上绘制更新的图像而言,帧的处理速度太快了,所以我加入了睡眠线,以将其降低到视频的帧速率,但这不起作用 代码如下:Ios 无法使用AVAssetTrackReaderOutput在while循环中更新UIViewImage,ios,swift,uikit,avfoundation,Ios,Swift,Uikit,Avfoundation,我试图从视频中提取每一帧,进行一些图像处理,然后将图像显示回UIImageView 如果我手动单击UIButton,图像将显示并迭代整个视频,并显示每个帧 但是,如果我将更新显示嵌入while循环,则视图不会更新(即,在设备上它不会更新) 我认为这是因为相对于在屏幕上绘制更新的图像而言,帧的处理速度太快了,所以我加入了睡眠线,以将其降低到视频的帧速率,但这不起作用 代码如下: import UIKit import Foundation import Vision import AVFounda
import UIKit
import Foundation
import Vision
import AVFoundation
import Darwin
class ViewController: UIViewController {
var uiImage: UIImage?
var displayLink: CADisplayLink?
var videoAsset: AVAsset!
var videoTrack: AVAssetTrack!
var videoReader: AVAssetReader!
var videoOutput: AVAssetReaderTrackOutput!
@IBOutlet weak var topView: UIImageView!
@IBOutlet weak var bottomView: UIImageView!
@IBOutlet weak var rightLabel: UILabel!
@IBOutlet weak var leftLabel: UILabel!
@IBAction func tapButton(_ sender: Any) {
while let sampleBuffer = videoOutput.copyNextSampleBuffer() {
print ("sample at time \(CMSampleBufferGetPresentationTimeStamp(sampleBuffer))")
if let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) {
let ciImage = CIImage(cvImageBuffer: imageBuffer)
uiImage = UIImage(ciImage: ciImage)
self.topView.image = uiImage
self.topView.setNeedsDisplay()
usleep(useconds_t(24000))
}
}
}
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewDidAppear(_ animated: Bool) {
guard let urlPath = Bundle.main.path(forResource: "video1", ofType: "mp4") else {
print ("No File")
return
}
videoAsset = AVAsset(url: URL(fileURLWithPath: urlPath))
let array = videoAsset.tracks(withMediaType: AVMediaType.video)
videoTrack = array[0]
do {
videoReader = try AVAssetReader(asset: videoAsset)
} catch {
print ("No reader created")
}
videoOutput = AVAssetReaderTrackOutput(track: videoTrack, outputSettings: [kCVPixelBufferPixelFormatTypeKey as String: kCVPixelFormatType_420YpCbCr8BiPlanarFullRange])
videoReader.add(videoOutput)
videoReader.startReading()
}
}
在你的情况下,你应该使用计时器,而不是睡觉。请尝试以下操作:
let frameDuration: TimeInterval = 1.0/60.0 // Using 60 FPS
Timer.scheduledTimer(withTimeInterval: frameDuration, repeats: true) { timer in
guard let sampleBuffer = videoOutput.copyNextSampleBuffer() else {
timer.invalidate()
return
}
print ("sample at time \(CMSampleBufferGetPresentationTimeStamp(sampleBuffer))")
if let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) {
let ciImage = CIImage(cvImageBuffer: imageBuffer)
uiImage = UIImage(ciImage: ciImage)
self.topView.image = uiImage
self.topView.setNeedsDisplay()
}
}
您的情况中的问题是,在执行此操作时,您仍然处于主线程上。所以当你睡觉的时候,你不会让你的主线程继续。因此,基本上你的主线程是构建图像和睡眠,但你没有给它时间来实际更新用户界面
您可以使用单独的线程执行类似的操作。例如,一个简单的分派就可以了:
DispatchQueue(label: "Updating images").async {
// Now on separate thread
while let sampleBuffer = videoOutput.copyNextSampleBuffer() {
print ("sample at time \(CMSampleBufferGetPresentationTimeStamp(sampleBuffer))")
if let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) {
let ciImage = CIImage(cvImageBuffer: imageBuffer)
uiImage = UIImage(ciImage: ciImage)
// The UI part now needs to go back to main thread
DispatchQueue.main.async {
self.topView.image = uiImage
self.topView.setNeedsDisplay()
}
usleep(useconds_t(24000))
}
}
}
但仍然要更新(至少)主线程上的UIKit部件,这一点很重要。甚至CI部件也可能需要在主线程上。最好试试看。在你的情况下,你应该使用计时器,而不是睡觉。请尝试以下操作:
let frameDuration: TimeInterval = 1.0/60.0 // Using 60 FPS
Timer.scheduledTimer(withTimeInterval: frameDuration, repeats: true) { timer in
guard let sampleBuffer = videoOutput.copyNextSampleBuffer() else {
timer.invalidate()
return
}
print ("sample at time \(CMSampleBufferGetPresentationTimeStamp(sampleBuffer))")
if let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) {
let ciImage = CIImage(cvImageBuffer: imageBuffer)
uiImage = UIImage(ciImage: ciImage)
self.topView.image = uiImage
self.topView.setNeedsDisplay()
}
}
您的情况中的问题是,在执行此操作时,您仍然处于主线程上。所以当你睡觉的时候,你不会让你的主线程继续。因此,基本上你的主线程是构建图像和睡眠,但你没有给它时间来实际更新用户界面
您可以使用单独的线程执行类似的操作。例如,一个简单的分派就可以了:
DispatchQueue(label: "Updating images").async {
// Now on separate thread
while let sampleBuffer = videoOutput.copyNextSampleBuffer() {
print ("sample at time \(CMSampleBufferGetPresentationTimeStamp(sampleBuffer))")
if let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) {
let ciImage = CIImage(cvImageBuffer: imageBuffer)
uiImage = UIImage(ciImage: ciImage)
// The UI part now needs to go back to main thread
DispatchQueue.main.async {
self.topView.image = uiImage
self.topView.setNeedsDisplay()
}
usleep(useconds_t(24000))
}
}
}
但仍然要更新(至少)主线程上的UIKit部件,这一点很重要。甚至CI部件也可能需要在主线程上。最好尝试一下。您正在阻止“主”线程-阻止它更新UIU您正在阻止“主”线程-阻止它更新UIHanks。我使用了您的建议,将帧抓取器部分卸载到单独的线程中,谢谢。我使用了您的建议,将帧抓取器部分卸载到单独的线程