Vorbis dev - May 2004 - Can vorbisfile read comments from an HTTP stream

Just noticed this article on Slashdot:

 http://ask.slashdot.org/article.pl?sid=04/05/18/0432202

...about the feasibility and efficiency of reading id3v2 tags out of mp3's 
over http. I know that vorbisfile's callback model is well suited to
handling
this sort of scenario, but I'm curious to know whether ov_open will try to 
read enough stream to pull the comments out on a non-seekable stream.
I've only played around with it on seekable streams, where it tries to scan 
the whole stream to get a count of the logical streams within.

Would ov_test get enough header read to determine the size of the comment 
before sucking it all in for parsing?

John
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On Wed, May 19, 2004 at 03:26:18AM +1200, John Morton
wrote:
> Just noticed this article on Slashdot:
> 
>  http://ask.slashdot.org/article.pl?sid=04/05/18/0432202
> 
> ...about the feasibility and efficiency of reading id3v2 tags out of
mp3's
> over http. I know that vorbisfile's callback model is well suited to
handling
> this sort of scenario, but I'm curious to know whether ov_open will try
to
> read enough stream to pull the comments out on a non-seekable stream.
> I've only played around with it on seekable streams, where it tries to
scan
> the whole stream to get a count of the logical streams within.
> 
> Would ov_test get enough header read to determine the size of the comment 
> before sucking it all in for parsing?
Not having done any verification, if you mark the stream as not 
seekable, vorbisfile should do what you want here. It must of course
parse it linearly, and will suck up all the headers before any audio
is decodeable.

The hard part might be knowing when to stop feeding it data. You can 
probably just pull on ov_read() once an then look at the 
OggVorbis_File->vorbis_comment struct.

If this is a stand-alone app, you might do better just using ogg (or ogg 
and vorbis, but not vorbisfile) directly. If you're just parsing the 
comment header, you don't need all the extra code.

 -r
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