Question

I’m using Matt 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?

Answer 1

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.