在Swift(iOS)中从视频创建帧

Question

有一个持续时间为3秒的视频文件。我需要创建30帧-UIImages。每0.1秒捕获一次图像。我试着使用AVAssetImageGenerator和CMTimeMake，但我总是得到30个类似的图像，或者15个类似的图片和15个其他类似的图片。

请帮助理解如何从这个视频中制作这种幻灯片。或者也许有更好的方法。

请参阅下面的代码：

static func generate_Thumbnails(forVideoWithURL url : URL) -> [UIImage]? {
let asset = AVAsset(url: url)
var result: [UIImage] = []
let assetImgGenerator = AVAssetImageGenerator(asset: asset)
assetImgGenerator.appliesPreferredTrackTransform = true
for i in 1...30 {
let time: CMTime = CMTimeMake(value: Int64(i), timescale: 10)
do {
let img: CGImage = try assetImgGenerator.copyCGImage(at: time, actualTime: nil)
let frameImg: UIImage = UIImage(cgImage: img)
result.append(frameImg)
} catch {
//return nil
}
}
return result
}

Answer 1

我尝试了Amin Benarieb的解决方案，它似乎有效：

static func toImages(fromVideoUrl url: URL) -> [UIImage]? {
let asset = AVAsset(url: url)
guard let reader = try? AVAssetReader(asset: asset) else { return nil }
let videoTrack = asset.tracks(withMediaType: .video).first!
let outputSettings = [String(kCVPixelBufferPixelFormatTypeKey): NSNumber(value: kCVPixelFormatType_32BGRA)]
let trackReaderOutput = AVAssetReaderTrackOutput(track: videoTrack, outputSettings: outputSettings)
reader.add(trackReaderOutput)
reader.startReading()
var images = [UIImage]()
while reader.status == .reading {
autoreleasepool {
if let sampleBuffer = trackReaderOutput.copyNextSampleBuffer() {
if let imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer) {
let ciImage = CIImage(cvImageBuffer: imageBuffer)
images.append(UIImage(ciImage: ciImage))
}
}
}
}
return images
}

Answer 2

我没有读过AVAssetImageGenerator的文档，但在实践中，我每秒只能生成1个图像。因此，您应该能够在1、2和3秒(但不是30秒(时获得图像。这是我用来生成图像的代码，与您的代码非常相似。

private func getPreviewImage(forURL url: URL, atSeconds seconds: Double) -> UIImage? {
let asset = AVURLAsset(url: url)
let generator = AVAssetImageGenerator(asset: asset)
generator.appliesPreferredTrackTransform = true
let timestamp = CMTime(seconds: seconds, preferredTimescale: 100)
do {
let imageRef = try generator.copyCGImage(at: timestamp, actualTime: nil)
return UIImage(cgImage: imageRef)
}
catch let error as NSError
{
print("Image generation failed with error (error)")
return nil
}
}