swift - 无法从 ios 13 中的 url 视频生成缩略图

Question

我正在使用下面的代码从视频 URL 生成一个帧。这段代码在之前的一段时间内运行良好。现在它不起作用。它抛出无法解码的错误并且文件可能已损坏。有人可以帮忙吗？

func previewImageFromVideo(url: NSURL) -> UIImage? {
        let url = url as URL
        let request = URLRequest(url: url)
        let cache = URLCache.shared

        if
            let cachedResponse = cache.cachedResponse(for: request),
            let image = UIImage(data: cachedResponse.data)
        {
            return image
        }

        let asset = AVAsset(url: url)
        let imageGenerator = AVAssetImageGenerator(asset: asset)
        imageGenerator.appliesPreferredTrackTransform = true
        imageGenerator.maximumSize = CGSize(width: 250, height: 120)

        var time = asset.duration
        time.value = min(time.value, 2)

        var image: UIImage?

        do {
            let cgImage = try imageGenerator.copyCGImage(at: time, actualTime: nil)
            image = UIImage(cgImage: cgImage)
        } catch { }

        if
            let image = image,
            let data = UIImagePNGRepresentation(image),
            let response = HTTPURLResponse(url: url, statusCode: 200, httpVersion: nil, headerFields: nil)
        {
            let cachedResponse = CachedURLResponse(response: response, data: data)

            cache.storeCachedResponse(cachedResponse, for: request)
        }

        return image
    }

此代码在从 URL 视频捕获帧时抛出错误。它说文件可能已损坏。

Answer 1

我在 Playground 上试过你的代码，它工作得很好。如错误消息所述，文件可能已损坏。

import UIKit
import AVKit
import PlaygroundSupport

let container = UIView(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
let imageView = UIImageView(frame: CGRect(x: 0, y: 0, width: 200, height: 200))
container.addSubview(imageView)

PlaygroundPage.current.liveView = container
PlaygroundPage.current.needsIndefiniteExecution = true

func previewImageFromVideo(url: NSURL) -> UIImage? {
    let url = url as URL
    let request = URLRequest(url: url)
    let cache = URLCache.shared

    if
        let cachedResponse = cache.cachedResponse(for: request),
        let image = UIImage(data: cachedResponse.data)
    {
        return image
    }

    let asset = AVAsset(url: url)
    let imageGenerator = AVAssetImageGenerator(asset: asset)
    imageGenerator.appliesPreferredTrackTransform = true
    imageGenerator.maximumSize = CGSize(width: 250, height: 120)

    var time = asset.duration
    time.value = min(time.value, 2)

    var image: UIImage?

    do {
        let cgImage = try imageGenerator.copyCGImage(at: time, actualTime: nil)
        image = UIImage(cgImage: cgImage)
    } catch { }

    if
        let image = image,
        let data = image.pngData(),
        let response = HTTPURLResponse(url: url, statusCode: 200, httpVersion: nil, headerFields: nil)
    {
        let cachedResponse = CachedURLResponse(response: response, data: data)

        cache.storeCachedResponse(cachedResponse, for: request)
    }

    return image
}

imageView.image = previewImageFromVideo(url: NSURL(string: "https://www.w3schools.com/html/mov_bbb.mp4")!)