is it possible to read metadata using HTTP live streaming in the iPhone SDK

Question

When playing a live stream using the HTTP Live Streaming method, is it possible read the current metadata (eg. Title and Artist)? This is for an iPhone radio app.

Answer 1

It is, but it's not easy. Matt Gallagher has a nice post on his blog about streaming audio. To quote him on the subject:

The easiest source of metadata comes from the HTTP headers. Inside the handleReadFromStream:eventType: method, use CFReadStreamCopyProperty to copy the kCFStreamPropertyHTTPResponseHeader property from the CFReadStreamRef, then you can use CFHTTPMessageCopyAllHeaderFields to copy the header fields out of the response. For many streaming audio servers, the stream name is one of these fields.

The considerably harder source of metadata are the ID3 tags. ID3v1 is always at the end of the file (so is useless when streaming). ID3v2 is located at the start so may be more accessible.

I've never read the ID3 tags but I suspect that if you cache the first few hundred kilobytes of the file somewhere as it loads, open that cache with AudioFileOpenWithCallbacks and then read the kAudioFilePropertyID3Tag with AudioFileGetProperty you may be able to read the ID3 data (if it exists). Like I said though: I've never actually done this so I don't know for certain that it would work.