From: pcrawfor <pcrawfor@...>
Date: 2007-12-16T01:10:03+09:00
Subject: Re: Work with Audio Files

On Dec 14, 5:48 pm, John Joyce <dangerwillrobinsondan...@gmail.com>
wrote:
> On Dec 14, 2007, at 7:12 PM, Konrad Meyer wrote:
>
>
>
> > Quoth Petr Kout:
> >> Lloyd Linklater wrote:
> >>> Petr Kout wrote:
> >>>> Hi,
>
> >>>> 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 plugin
> >>>> 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 all
> >>>> over Google, nothing found. Thank you very much for any advice.
>
> >>>http://www.ruby-forum.com/topic/130804#new
>
> >> Hi,
>
> >> 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.
>
> >> Thanks.
>
> >> Peter
>
> > There is a great library out in the wild called "metadata" that you
> > can use to
> > get information about mp3s (as well as many other filetypes) that I
> > think is
> > available in gem form. You might take a look at that.
>
> > If you want to truncate a constant bitrate mp3, AFAIK they are
> > structured such
> > that you *could* crudely lop off some bytes from the end (channels *
> > time_to_clip * bitrate bytes). If not, you'll need to use some sort of
> > external mp3 library. I don't know of any that exist with ruby
> > bindings. You
> > might look at LAME though I'm not sure how much that will do.
>
> > HTH,
> > --
> > Konrad Meyer <kon...@tylerc.org>http://konrad.sobertillnoon.com/
>
> Remember, keyword there was CONSTANT bitrate, variable bitrate might
> give you more trouble doing that without more care.
> Be sure any meta data matches changes or some apps might complain
> about the audio file.

Hey,

There is a useful library ID3Lib that supports reading mp3 tags, and a
ruby wrapper for that library id3lib-ruby that is available as a gem
which I have used to read and modify mp3 files.

Paul