| Subject: | Stream extraction and tag rendering |
| Cc: | pastorofmuppets [...] users.sf.net |
From Steve Sloan (pastorofmuppets at users.sf.net), moved to new RT system:
In my current project, I want to read the ID3 tag from
a file, store the info in a database, then strip-out
the tag and store just the MPEG data in a file. To
export a song from the database, I just spit-out the
MPEG data and attach an ID3 tag (v1.1), rendered
on-the-fly.
These is difficult to implement without access to
MP3::Info's internal data, so I propose adding two
functions:
(1) map_mp3data( $file, $function, $buffsize = 4096 )
This opens the file (or filehandle) passed and
computes the start and end points of the MPEG stream
(i.e. after the V2 tag and before the V1 tag). It then
reads the data, $buffsize bytes at a time, and calls
the function-reference $function, with the current
buffer as $_. This would allow for easy processing of
MPEG data (e.g. decoding/playing).
(2) render_mp3tag( ... )
This function behaves the same as set_mp3tag(),
except without the file argument, and instead of
modifying the tag in the file, it renders the new tag
(V1.1) and returns it in binary form.
The grunt work for both of these functions is already
present, only requiring some code rearrangement. E.g.
set_mp3tag() would call render_mp3tag() to generate the
tag, then write it to the file. remove_mp3tag() could
call map_mp3data() in cases where a simple file
truncate won't do (i.e. V2 tag present).
I've attached my version of MP3::Info with these
changes. They should probably be implemented a bit
more cleanly, but in either case, I strongly urge you
to add this functionality.
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