I\'ve been having quite a difficult time extracting ID3 information from an MP3 being streamed over Live HTTP Streaming (using the Wowza media server, if anyone is curious).
Instead of using commonMetadata you might want to try using timedMetadata on the AVPlayerItem:
commonMetadata
timedMetadata
AVPlayerItem
[playerItem addObserver:self forKeyPath:@"timedMetadata" options:NSKeyValueObservingOptionNew context:NULL];