AVAggregateAssetDownloadTask Error Domain=CoreMediaErrorDomain Code=-16657

Question

I'm using AVAggregateAssetDownloadTask to download HLS videos in my application. I just added a pause/resume functionality. Simply, I'm suspending the task when the user wants to pause the download.

But, somehow in this case, actually task won't stop. It keeps downloading the asset. When I press the resume button I'm calling the task's .resume() method. Somehow, the process going super fast till the %100, and it gives an error (keep reading or goto Error Message title).

How do I test

• Start to download an item via AVAggregateAssetDownloadTask
• Tap Pause at the %3.
• Call the task?.suspend()
• Wait for 1 minute or 2
• Tap the resume download button
• Call the task?.resume()
• Task resumes from %29
• Task fails at %48

Code

@objc public func pauseDownload(for productId: String) {
    var asset: Asset?
    var task: AVAggregateAssetDownloadTask?
    for (taskKey, assetValue) in activeDownloadsMap where productId == assetValue.productId {
        asset = assetValue
        task = taskKey
        task?.suspend() // **task is not nil!**
        break
    }

    // Here: I'm sending a notification to the UI cases
}

@objc public func resumeDownload(for productId: String) {
    var asset: Asset?
    var task: AVAggregateAssetDownloadTask?
    for (taskKey, assetValue) in activeDownloadsMap where productId == assetValue.productId {
        asset = assetValue
        task = taskKey
        task?.resume() // **task is not nil!**
        break
    }

    // Here: I'm sending a notification to the UI cases
}

Other Cases

• Without suspending the task, it downloads flawlessly.

Technical Details

• Xcode Version 12.4 (12D4e)
• iOS Version 14.4

Error Message

Error Domain=CoreMediaErrorDomain Code=-16657

"(null)" UserInfo={_NSURLErrorRelatedURLSessionTaskErrorKey=( "BackgroundAVAssetDownloadTask .<1>"), _NSURLErrorFailingURLSessionTaskErrorKey=BackgroundAVAssetDownloadTask .<1>}

developer.apple.com

Here is the same issue at developer.apple.com:

https://developer.apple.com/forums/thread/674090

Reported Bug

FB9043262

If you believe you are faced with the same issue, please consider the help.

Best.

Answer 1

I just had this error on iOS 16.1

Error Domain=CoreMediaErrorDomain Code=-16657 "(null)" UserInfo={_NSURLErrorRelatedURLSessionTaskErrorKey=(
    "BackgroundAVAssetDownloadTask <6B7F1201-FF3E-4B81-B3C5-6C85D8718BDA>.<2>"
), _NSURLErrorFailingURLSessionTaskErrorKey=BackgroundAVAssetDownloadTask <6B7F1201-FF3E-4B81-B3C5-6C85D8718BDA>.<2>}

It seems that a change in AVAggregateAssetDownloadTask as part of iOS16 is causing the the root .m3u8 to be retrieved multiple times.

We generate these root .m3u8 playlists on-the-fly and put a token on URIs pointing to child subtitle .m3u8 files. Each time the root playlist was retrieved a new token was generated, and it had a slightly different URI for the subtitle playlist. In a proxyman network trace, we could see both subtitle playlists being retrieved, and the eventual .vtt subtitle files coming from the URIs specified in the second playlist.

Ensuring a consistent URI value for the subtitle playlist across multiple root playlist retrievals fixed the issue.