Get MP3 ID3 meta data and song duration using AudioStreamer

I'm using Ma开发者_如何学Gott Gallagher's AudioStreamer to play MP3s over HTTP. I need to know the duration of the song and the ID3 tags.

Is it possible to implement this in the AudioStreamer, and how?

---

From his Docs:

Limited scope

One point should be clarified before I continue: this class is intended for streaming audio. By streaming, I don't simply mean "an audio file transferred over HTTP". Instead, I mean a continuous HTTP source without an end that continues indefinitely (like a radio station, not a single song).

This seems to imply that getting the duration might be tough.

Here is how to get the ID3v2 tags:

Get metadata

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.

---

MP3 streams are divided into 'frames' which are single units of data. Some streams do add a ID3 metadata block every few frames which you could theoretically scan for and read.

See here for more information: http://jicyshout.sourceforge.net/oreilly-article/java-streaming-mp3-pt2/java-streaming-mp3-pt2.html