AVAssetDownloadDelegate methods for HLS caching not getting called

Question

I have followed the tutorial given here for HLS caching, but the control never reaches to any of the delegates ( of AVAssetDownloadDelegate ).

Am I missing anything? Here is code I wrote

- (void)setupAssetDownloader {
    NSURL *assetURL = [NSURL URLWithString:@"STREAMING_HOST/video/hls/3729170.m3u8"];
    AVURLAsset *hlsAsset = [AVURLAsset assetWithURL:assetURL];

    urlSessionConfiguration = [NSURLSessionConfiguration backgroundSessionConfigurationWithIdentifier:@"assetDowloadConfigIdentifier"];
    avAssetDownloadSession = [AVAssetDownloadURLSession sessionWithConfiguration:urlSessionConfiguration assetDownloadDelegate:self delegateQueue:[NSOperationQueue mainQueue]];

    // Download movie
    avAssetDownloadTask = [avAssetDownloadSession assetDownloadTaskWithURLAsset:hlsAsset assetTitle:@"downloadedMedia" assetArtworkData:nil options:nil];

//@{AVAssetDownloadTaskMinimumRequiredMediaBitrateKey : @(300000)}


    [avAssetDownloadTask resume];

    AVPlayerItem *playerItem = [[AVPlayerItem alloc] initWithAsset:avAssetDownloadTask.URLAsset];
    AVPlayer *player = [[AVPlayer alloc ] initWithPlayerItem:playerItem];
    AVPlayerLayer *playerLayer = [[AVPlayerLayer alloc ] init];
    [playerLayer setPlayer:player];
    [playerLayer setFrame:self.view.frame];
    [self.view.layer addSublayer:playerLayer];
    [player play];
}

#pragma mark - AVAssetDownloadDelegate

- (void)URLSession:(NSURLSession *)session assetDownloadTask:(AVAssetDownloadTask *)assetDownloadTask didResolveMediaSelection:(AVMediaSelection *)resolvedMediaSelection {

}
- (void)URLSession:(NSURLSession *)session assetDownloadTask:(AVAssetDownloadTask *)assetDownloadTask didLoadTimeRange:(CMTimeRange)timeRange totalTimeRangesLoaded:(NSArray<NSValue *> *)loadedTimeRanges timeRangeExpectedToLoad:(CMTimeRange)timeRangeExpectedToLoad {
    NSInteger percent = 0;
    for (NSValue *value in loadedTimeRanges) {
        CMTimeRange timeRange = [value CMTimeRangeValue];
        percent += CMTimeGetSeconds(timeRange.duration) / CMTimeGetSeconds(timeRangeExpectedToLoad.duration);
    }
    percent *= 100;
    NSLog(@"Progress: %ld", (long)percent);
}

- (void)URLSession:(NSURLSession *)session assetDownloadTask:(AVAssetDownloadTask *)assetDownloadTask didFinishDownloadingToURL:(NSURL *)location {
    NSString *localPath = location.relativePath;
    NSLog(@"localPath: %@", localPath);
    // TODO: Play downloaded file
    // IMPORTANT: Don't move this file to another location.
}

Reproof

This was a very helpful example regardless of the question. Thank you! – Bulletproof

Answer 1

I was running the code on simulator and

Downloading HLS streams is not supported on simulator.

I figured it out when I used the delegate method mentioned below.

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error {

}

And now struggling for the whole day, I found a sample by Apple here and got the real reason behind the problem.

Reproof

Hey, I'm running the same code on device but still my delegate methods are not called, any idea? – Dressmaker

Answer 2

I recently came across the same symptoms.

Turns out I had another object in my app that setup a background URL session.

let configuration = URLSessionConfiguration.background(withIdentifier: "[id]") 

As soon as I removed that other session, I started to get the expected callbacks.

Maybe it's documented somewhere that an app shouldn't setup multiple background download sessions, but in any case this solved my problem.

Secant