Reloading keys in AVAsset when status is AVKeyValueStatusFailed

问题

I'm doing the following:

Create a new AVAsset with a given URL. That URL points to a video on a remote web server.
Attempt to load the tracks property by calling loadValuesAsynchronouslyForKeys:completionHandler:
The initial request fails, because no internet connection exists
I notice that the request failed by calling statusOfValueForKey:error:
I then wait for the connection to re-appear (using some reachability code). As soon as it does, I call loadValuesAsynchronouslyForKeys:completionHandler: again.

Here's where the problems begin. I would imagine that the AVAsset goes ahead and attempts to reload the tracks property since it failed previously. However, this does not seem to happen. statusOfValueForKey:error: will still return AVKeyValueStatusFailed, although a working internet connection is available and the video is playable.

Is there a way to reset the state for this given property and to attempt another load? Is there another way to work around this?

回答1:

Are you creating a new AVURLAsset or just reusing the previous one?
In the completion handler for loadValuesAsynchronouslyForKeys:completionHandler: are you dispatching back to the main thread?

What happens if you call this method again (or something similar) when you're ready to retry.

- (void)setContentURL:(NSURL *)contentURL
{
    if (_contentURL != contentURL) {
        _contentURL = contentURL;

        AVURLAsset *asset = [AVURLAsset URLAssetWithURL:_contentURL options:nil];

        NSArray *requestedKeys = [NSArray arrayWithObjects:ISIVideoPlayerControllerTracksKey, ISIVideoPlayerControllerPlayableKey, nil];

        [asset loadValuesAsynchronouslyForKeys:requestedKeys completionHandler: ^{
             dispatch_async(dispatch_get_main_queue(), ^{
                 [self prepareToPlayAsset:asset withKeys:requestedKeys];
             });
         }];
    }
}

来源：https://stackoverflow.com/questions/21139806/reloading-keys-in-avasset-when-status-is-avkeyvaluestatusfailed

标签

ios

avfoundation

avasset