swift -不能播放带有AVAssetResourceLoaderDelegate的视频

Question

我试着用AVPlayer播放一个加载在AVAssetResourceLoaderDelegate中的视频，但是我总是得到一个空白的屏幕，而这个视频从未播放过。

这是代码：

let asset = AVURLAsset(url: URL(string: "fakescheme://video.mp4")!)
asset.resourceLoader.setDelegate(ResourceLoaderDelegate(), queue: DispatchQueue.main)
let item = AVPlayerItem(asset: asset)
let player = AVPlayer(playerItem: item)

let playerLayer = AVPlayerLayer(player: self.player)
playerLayer!.frame = self.view.bounds;
self.view.layer.addSublayer(self.playerLayer!)
player!.play()

...

class ResourceLoaderDelegate: NSObject, AVAssetResourceLoaderDelegate, URLSessionDelegate, URLSessionDataDelegate, URLSessionTaskDelegate {
    public func resourceLoader(_ resourceLoader: AVAssetResourceLoader, shouldWaitForLoadingOfRequestedResource resourceLoadingRequest: AVAssetResourceLoadingRequest) -> Bool {

        var newRequest = URLRequest(url: URL(string: "https://example.com/video.mp4")!)
        newRequest.allHTTPHeaderFields = resourceLoadingRequest.request.allHTTPHeaderFields

        let sessionTask = URLSession.shared.dataTask(with: newRequest) { data, response, error in
            resourceLoadingRequest.contentInformationRequest?.contentType = "video/mp4"
            resourceLoadingRequest.contentInformationRequest?.isByteRangeAccessSupported = true
            resourceLoadingRequest.contentInformationRequest?.contentLength = Int64(data.count)

            resourceLoadingRequest.response = response

            resourceLoadingRequest.dataRequest?.respond(with: data)
            resourceLoadingRequest.finishLoading()
        }

        sessionTask.resume()
        return true
    }
}

这是基本的想法：

fakescheme://导致调用resourceLoader()委托，其中发出一个新的HTTP请求来下载实际的视频。

然后它调用resourceLoadingRequest.dataRequest?.respond(with:数据)，这应该会导致AVPlayer播放下载的视频。数据变量已正确填充，但我始终得到一个黑色屏幕。

视频文件也很好，如果我将它直接输入到AVURLAsset()中，它就会播放。

我尝试了无数的东西和组合，但不能让它发挥使用委托。任何帮助都将不胜感激！

编辑:我会添加更多的信息。

我试着用AES加密的视频做这件事，其中它使用了3个文件-- .m3u8、加密密钥和.ts视频。我成功地让它使用委托下载了.m3u8和密钥，但是当我尝试用视频文件下载它时，我的屏幕就变黑了。

这导致我认为可能需要下载部分，但我不知道如何正确地做到这一点。我也找不到关于它的任何文档，例如-应该设置headers，就像它来自web服务器，应该设置contentInformationRequest等等。委托会被调用2次：

// first time: 
resourceLoadingRequest.dataRequest!.requestedLength == 2,
resourceLoadingRequest.dataRequest!.requestsAllDataToEndOfResource == false

// second time: 
resourceLoadingRequest.dataRequest!.requestedLength == MAX_INT,
resourceLoadingRequest.dataRequest!.requestsAllDataToEndOfResource == true

我不知道该做什么-我给它整个视频两次，但没有成功。

Answer 1

我终于让它开始工作了。因此，上面的代码有两个问题：

1. contentType应为AVFileType.mp4.rawValue，即"public.mpeg-4“。传递“视频/MP4”或另一个值会破坏它的

1. resourceLoadingRequest.dataRequest!.requestedLength确实需要得到尊重，因此视频文件需要按请求以块的形式发送。

这是工作委托代码：

// this IF is an ugly way to catch the first request to the delegate
// in this request you should populate the contentInformationRequest struct with the size of the video, etc
if (resourceLoadingRequest.dataRequest!.requestedLength == 2) {
    let bytes : [UInt8] = [0x0, 0x0] // these are the first 2 bytes of the video, as requested
    let data = Data(bytes: bytes, count: bytes.count)
    
    resourceLoadingRequest.contentInformationRequest?.contentType = AVFileType.mp4.rawValue // this is public.mpeg-4, video/mp4 does not work
    resourceLoadingRequest.contentInformationRequest?.isByteRangeAccessSupported = true
    resourceLoadingRequest.contentInformationRequest?.contentLength = Int64(videoSize)
    
    resourceLoadingRequest.dataRequest!.respond(with: data)
    resourceLoadingRequest.finishLoading()
    
    return true
}

// here we are at the second request. the OS may request the entire file, or a portion of it 
// here we don't need to set any headers or contentInformationRequest, just reply with the requested data
// take a look at resourceLoadingRequest.dataRequest!.requestedLength, requestedOffset, currentOffset, requestsAllDataToEndOfResource
resourceLoadingRequest.dataRequest?.respond(with: data)
resourceLoadingRequest.finishLoading()

return true

这是供参考的整个文件的代码：

import Foundation
import AVKit

class ResourceLoaderDelegate: NSObject, AVAssetResourceLoaderDelegate, URLSessionDelegate, URLSessionDataDelegate, URLSessionTaskDelegate {
    public func resourceLoader(_ resourceLoader: AVAssetResourceLoader, shouldWaitForLoadingOfRequestedResource resourceLoadingRequest: AVAssetResourceLoadingRequest) -> Bool {
        if ((resourceLoadingRequest.request.url?.absoluteString.contains(".mp4"))!) {
            // replace the fakeScheme and get the original video url
            var originalVideoURLComps = URLComponents(url: resourceLoadingRequest.request.url!, resolvingAgainstBaseURL: false)!
            originalVideoURLComps.scheme = "file"
            let originalVideoURL = originalVideoURLComps.url
            
            var videoSize = 0
            do {
                let value = try originalVideoURL!.resourceValues(forKeys: [.fileSizeKey])
                videoSize = value.fileSize!
            } catch {
                print("error getting video size")
            }
            
            if (resourceLoadingRequest.contentInformationRequest != nil) {
                // this is the first request where we should tell the OS what file is to be downloaded
                let bytes : [UInt8] = [0x0, 0x0]    // TODO: repeat .requestedLength times?
                let data = Data(bytes: bytes, count: bytes.count)
                
                resourceLoadingRequest.contentInformationRequest?.contentType = AVFileType.mp4.rawValue // this is public.mpeg-4, video/mp4 does not work
                resourceLoadingRequest.contentInformationRequest?.isByteRangeAccessSupported = true
                resourceLoadingRequest.contentInformationRequest?.contentLength = Int64(videoSize)
                
                resourceLoadingRequest.dataRequest!.respond(with: data)
                resourceLoadingRequest.finishLoading()
                
                return true
            }
            
            // this is the second request where the actual file is to be downloaded
            
            let requestedLength = resourceLoadingRequest.dataRequest!.requestedLength
            let requestedOffset = resourceLoadingRequest.dataRequest!.requestedOffset
            let buffer = UnsafeMutablePointer<UInt8>.allocate(capacity: requestedLength)
            
            let inputStream = InputStream(url: originalVideoURL!)   // TODO: keep the stream open until a new file is requested?
            inputStream!.open()
            
            if (requestedOffset > 0) {
                // move the stream pointer to the requested position
                let buffer2 = UnsafeMutablePointer<UInt8>.allocate(capacity: Int(requestedOffset))
                inputStream!.read(buffer2, maxLength: Int(requestedOffset)) // TODO: the requestedOffset may be int64, but this gets truncated to int!
                buffer2.deallocate()
            }
            inputStream!.read(buffer, maxLength: requestedLength)
            
            // decrypt the video
            if (requestedOffset == 0) { // TODO: this == 0 may not always work?
                // if you use custom encryption, you can decrypt the video here, buffer[] holds the bytes
            }
        
            let data = Data(bytes: buffer, count: requestedLength)
            
            resourceLoadingRequest.dataRequest?.respond(with: data)
            resourceLoadingRequest.finishLoading()
            
            buffer.deallocate()
            inputStream!.close()
            
            return true
        }
        
        return false
    }
}