swift - cannot play a video loaded with AVAssetResourceLoaderDelegate - swift

Question

I'm trying to play a video with AVPlayer that was loaded inside AVAssetResourceLoaderDelegate but I always get a blank screen and the video never plays.
This is the code:
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
}
}
This is the basic idea:
The fakescheme:// causes the resourceLoader() delegate to be called, inside it a new HTTP request is made to download the actual video.
And then it calls resourceLoadingRequest.dataRequest?.respond(with: data) that was supposed to cause AVPlayer to play the downloaded video.
The data variable is properly populated, but yet I always get a black screen.
The video file is also fine, it plays if I feed it directly into AVURLAsset().
I tried a million things and combinations, but can't make it play using the delegate. Any help will be greatly appreciated!
EDIT: I'll add some more info.
I tried doing this with an AES encrypted video where it uses 3 files - .m3u8, the encryption key and the .ts video.
I managed to make it download the .m3u8 and the key using the delegate, but again when I try to do it with the video file, I get black screen.
This leads me to thinking it may require the download to happen in portions, but I'm not sure how to properly do that.
I also can't find any documentation about it, such as - should you set the HTTP headers as if this is coming from a web server, should you set contentInformationRequest, etc. The delegate gets called 2 times:
// first time:
resourceLoadingRequest.dataRequest!.requestedLength == 2,
resourceLoadingRequest.dataRequest!.requestsAllDataToEndOfResource == false
// second time:
resourceLoadingRequest.dataRequest!.requestedLength == MAX_INT,
resourceLoadingRequest.dataRequest!.requestsAllDataToEndOfResource == true
I'm not sure what to make of that - I give it the entire video both times, but no success.

Answer 1

I finally got it to work. So there are 2 problems with the above code:
contentType should be AVFileType.mp4.rawValue, which is "public.mpeg-4". Passing "video/mp4" or another value breaks it
resourceLoadingRequest.dataRequest!.requestedLength Indeed needs to be respected, so the video file needs to be sent in chunks as requested.
This is the working delegate code:
// 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
This is the code of the whole file for reference:
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
}
}