How to reinit AVPlayerItem? - ios

Question

I am initializing AVPlayerItem with "initWithUrl:" method.
Issue is that when initialization is interrupted (e.g. connection is lost)
Let's say we have following:
self.avPlayerItem = [[AVPlayerItem alloc] initWithUrl:url];
1.
What should be done? What happens to instance of avPlayerItem when connection is lost meanwhile?
Is there some protocol to implement in order to identify if initialization was successful or not?
2.
What I have noticed is that once initialization is interrupted then next "successful" initialization of avPlayerItem doesn't have tracks at all (they are present when no interruption is done before)
To initialize avPlayerItem with tracks again from the source user needs to close and open the app again.

Answer 1

When dealing with code that relies on internet connection you have to make sure there are failsafes that kick in when something goes wrong, because at some point it will.
What should be done?
1) Perform all code that relies on internet connection on a background thread. You don't want to block up the UI.
2) If possible verify the downloaded file before using.
There are different ways of going about this but off the top of my head I think I would use NSURLConnection or similar API to download the file into a temp folder. ON A BACKGROUND THREAD.
When downloaded I would initialise an AVAsset using the temp URL. AVAsset has some nice properties like playable that will help you check that the file downloaded OK. (NSURLConnectionDelegate also has a method that notifies if there was an error downloading.)
If you've got this far then you can create an AVPlayerItem with your AVAsset and away you go. Remember to wipe the contents of your temp folder at some point if you're not hanging on to the downloaded content.
Remember that you want to play your file on the main thread but all other loading and checking is probably best done on a background thread; you definitely want to use NSURLConnection from a background thread.

Answer 2

Store the AVPlayerItem in an NSPurgeableData object first, and play from that; store the data object in an NSCache object to automatically evict the object from memory after it has played, or when the connection is dropped, and the former AVPlayerItem is replaced by a new one (all of these things you should be doing anyway, regardless of the particular problem you describe). Here's some code to get you started:
void (^cachePlayerItem)(AVPlayerItem *, NSCache *, NSString *) = ^(AVPlayerItem *playerItem, NSCache *cache, NSString *key) {
NSURL *fileURL = [(AVURLAsset *)playerItem.asset URL];
NSPurgeableData *data = [NSPurgeableData dataWithContentsOfURL:fileURL];
[data beginContentAccess];
[cache setObject:data forKey:key];
[data endContentAccess];
[data discardContentIfPossible];
};
Put this block anywhere in an implementation file, defining it in the header file with:
typedef void (^cachePlayerItemBlock)(AVPlayerItem *, NSCache *, NSString *);
Call it within a method with:
cachePlayerItem(playerItem, playerItems, phAsset.localIdentifier);
Whereas, playerItem is the AVPlayerItem, playerItems is the NSCache cache, and, depending on what kind of asset from which you are acquiring the AVPlayerItem, an identifier of some kind unique to it (or, in the example above, its associated asset).
By the way, I set up my caches in AppDelegate accordingly:
- (NSCache *)thumbnailCache {
__block NSCache *t = self->_thumbnailCache;
if (!t) {
t = [[NSCache alloc] init];
[t setName:#"Thumbnail Cache"];
[t setEvictsObjectsWithDiscardedContent:TRUE];
[t setCountLimit:self.assetsFetchResults.count];
self->_thumbnailCache = t;
}
return t;
}
This ensures not only global access to, but also one instance of, the cache, which is particularly important when caching AVPlayerItems, as they can be large in size.
To create a globally accessible cache in AppDelegate, add these to your header and implementation files, respectively:
+ (AppDelegate *)sharedAppDelegate;
...and:
+ (AppDelegate *)sharedAppDelegate
{
return (AppDelegate *)[[UIApplication sharedApplication] delegate];
}
To reference the cache in other class files, import the AppDelegate header file, and, if desired, create a shortcut to the AppDelegate's sharedApplication method:
#import "AppDelegate.h"
#define AppDelegate ((AppDelegate *)[[UIApplication sharedApplication] delegate])
Insodoing, the cache can be referenced by...:
AppDelegate.thumbnailCache
...instead of:
AppDelegate.sharedAppDelegate.thumbnailCache