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PoducateMe: Practical Solutions for Podcasting in Education
www.poducateme.com Web site and PoducateMe guide Copyright 2007 by Micah Ovadia.
Printable copies of the guide are available for purchase and immediate download at
http://www.poducateme.com/guide/purchase. Guide last updated 9/30/07.
We’ll be using LAME to encode our file. It offers superior quality and functionality than
that provided by the MP3 encoder included in iTunes. Many consider LAME the best MP3
encoder out there right now. 
Mac users can use Stephen F Booth’s Max (Free, Mac, (http://sbooth.org/Max/) for LAME
compression. PC users can use RazorLame, a PC front-end for the LAME encoder (PC,
Free, www.dors.de/razorlame/docs.php) available for download, but in order to use it, you
must download and install LAME for Windows (Free, PC, http://www-
users.york.ac.uk/~raa110/audacity/lame.html) separately.
Some LAME encoders will allow users to input “switch settings,” with which podcasters
can exercise extreme control over file encoding (Max doesn’t feature this capability, but
RazorLame does). Among these settings is a control for bitrate.
Measured in "bits per second," bitrate is used to express the rate at which data is
transmitted or processed. Higher bitrates mean bigger file sizes and generally better
audio quality. Lower bitrates produce smaller file sizes but typically inferior audio quality.
There are three types of MP3 bitrate encodes from which to choose:
Constant Bitrate (CBR)
CBR MP3s are the most common type of file found on the Internet. Files encoded
using CBR maintain the same user-defined bitrate for every part of the song, from
start to finish. Both complex and simpler parts of the file are given the same amount
of bandwidth.
Variable Bitrate (VBR)
During VBR compression, the encoder variably increases and decreases the bitrate
based on how much data is actually needed to precisely reproduce the source file.
For example, during dense music passages, the encoder increases the bandwidth as
needed. During simpler passages, such as speech, the encoder lowers the bitrate.
Using a high bitrate for speech is superfluous and only adds to file size.
Average Bitrate (ABR)
ABR is basically a blend of CBR and VBR. The similarity to CBR comes in the
encoder offering users the ability to choose a bitrate at which they wish to encode.
The encoder then begins processing the file in a manner similar to VBR, adjusting the
bandwidth as needed. During this process, the encoder attempts not to stray too far
from the bitrate specified by the user.
In General, VBR is better than ABR, which is better than CBR (except when you choose
the highest possible CBR bitrate, which is 320 kbps). So, why has CBR become the
standard? VBR technology was slow to catch on because of its initial bugginess and lack
of media players supporting the technology. We’ve been using CBR to encode
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Podcast Kits From zZounds
photoMicah Ovadia
University of Cincinnati
151 McMicken Hall