From: Konrad Meyer <konrad@...>
Date: 2007-12-15T10:12:39+09:00
Subject: Re: Work with Audio Files

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Quoth Petr Kout:
> Lloyd Linklater wrote:
> > Petr Kout wrote:
> >> Hi,
> >>=20
> >> I am new to Ruby on Rails and I consider converting my application
> >> written in Java into Ruby. The question is, however, is there any plug=
in
> >> or other way to handle MP3 and other audio files? I need to Ruby to be
> >> able to tell me how long the uploaded MP3 is and ideally, give me the
> >> possibility to cut the file on the server if it's too long. I looked a=
ll
> >> over Google, nothing found. Thank you very much for any advice.
> >=20
> > http://www.ruby-forum.com/topic/130804#new
>=20
> Hi,
>=20
> thank you for the link, but it's not what I was looking for. I do not
> need to play the mp3 file. I need to be able to analyze it on the
> backend; that is, to get its length in seconds, and possibly truncate it
> (not necessary). I was doing it in Java so far. If I can't do this on
> the backend, I can't switch to Ruby, which is what I would love to do.
>=20
> Thanks.
>=20
> Peter

There is a great library out in the wild called "metadata" that you can use=
 to=20
get information about mp3s (as well as many other filetypes) that I think i=
s=20
available in gem form. You might take a look at that.

If you want to truncate a constant bitrate mp3, AFAIK they are structured s=
uch=20
that you *could* crudely lop off some bytes from the end (channels *=20
time_to_clip * bitrate bytes). If not, you'll need to use some sort of=20
external mp3 library. I don't know of any that exist with ruby bindings. Yo=
u=20
might look at LAME though I'm not sure how much that will do.

HTH,
=2D-=20
Konrad Meyer <konrad@tylerc.org> http://konrad.sobertillnoon.com/

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