--- Forwarded Message from Derek Roff <[log in to unmask]> ---

>Date: Fri, 15 Sep 2006 15:01:25 -0600
>From: Derek Roff <[log in to unmask]>
>To: Language Learning and Technology International Information Forum
<[log in to unmask]>
>Subject: Re: #8321 Creating MP3s
>In-Reply-To: <[log in to unmask]>
>References:  <[log in to unmask]>

As Barbara mentioned, iTunes has three pre-set options, and a "Custom" 
choice for MP3 encoding bit rates, which reveals about a dozen options.  It 
also offers the possibility of variable bit rate encoding.

An element in the decision of MP3 bitrate is whether you will preserve an 
archive of the WAV files.  If you archive the WAV files, then you could 
choose a fairly modest MP3 bit rate for the student listening files.  You 
will be able to produce a higher quality MP3 file (or whatever replaces 
MP3) when needed.  If you plan to dump the WAV files, and the MP3s will be 
the archive, then you may want to record them at a higher bit rate.

I find 128 kbps to be perfectly acceptable to my ears for voice recording, 
and we don't have student or teacher complaints for material recorded at 
that bit rate.  However, I record mostly at 160 kbps and 192 kbps, because 
I haven't had a space shortage for storing the digital files.  If I had to 
digitize our whole analog collection, I would probably drop down to 128 
kpbs.

Especially at the lower bit rates, I would use the variable bit rate 
encoding option.  This option should offer better sound quality at the same 
average bit rate, although I haven't done any listening tests.

Derek

--On Friday, September 15, 2006 11:38 AM -0400 LLTI-Editor 
<[log in to unmask]> wrote:

> Language study at the University of Chicago is moving (fairly abruptly)
> into digital delivery. I have captured audio from tapes as .wav files
> (40 kHz, 16- or 24-bit). I want to convert these to mp3s files, but I
> find that iTunes (which I am using right now) gives me three pre-set
> options and then I can customize as I choose. Can anyone tell me what
> perceptible differences they have noticed among these various options?
> Good (128 kbps) and Higher (192) (both mono and 48 kHz) sound basically
> the same to me, with a 13 MB difference in size for the same material.
> What would 320 kbps get me? (Is there anyone out there doing phonetic
> analysis of language audio?)
>
> Barbara



Derek Roff
Language Learning Center
Ortega Hall 129, MSC03-2100
University of New Mexico
Albuquerque, NM 87131-0001
505/277-7368, fax 505/277-3885
Internet: [log in to unmask]



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