January 11, 2002, 12:00 AM — Why Change?
So you already have 2000 mp3 clips on your hard disk, a dedicated mp3
player, and an encoder for creating mp3 clips. Furthermore, you are
subscribed to one or more file sharing communities that enable you to
download and upload mp3 clips of almost anything that has ever been
recorded in that past 100 years. Why bother with a new format? After
all, isn't mp3 open?
No, it isn't. The MPEG consortium members claim that creating an mp3
encoder without using their patents is impossible. Worse yet, MPEG-4,
supposedly the next generation of Internet media streaming, is even
more tightly controlled.
In the past, we have seen outwardly open formats turning into closed,
proprietary standards whose owners charge royalties from their users.
If that doesn't sound troublesome enough, then collaboration between
the MPEG consortium and RIAA is becoming a tangible option.
Ogg Vorbis (http://www.xiph.org/ogg/index.html) is a fully open, non-
proprietary, patent-and-royalty-free, general purpose compressed audio
format for CD quality (44.1-48.0kHz sampling rate, 16+ bit resolution)
audio and music at fixed and variable bitrates ranging from 16 to 128
kbps per channel. In this regard, Vorbis is a viable competitor to
other audio encoding formats, including MPEG-1 audio layer 3, MPEG-4
audio, and PAC.
In terms of performance, Vorbis requires the same encoding and decoding
power as MP3. As the current Vorbis sources are still under development
and, therefore, unoptimized, Vorbis is likely to get faster in the
future. In terms of data compression rates, Vorbis is slightly better
Dispelling the Hype
Sadly, when it comes to open-source products, journalists often tend to
extol their miraculous qualities while omitting less pleasant aspect.
It's important to realize that Ogg Vorbis is still under development;
several important features including support for low bitrates, command
line interface, and real-time error correction haven't been implemented
yet. This will change in the coming weeks and months as the Vorbis
family of media streaming tools evolves and matures, yet DSP engineers
and CS students might frown when they discover that the Vorbis format
uses forward adaptive algorithms and MDCT, whereas wavelets (read more
on wavelets here:
http://www.amara.com/IEEEwave/IEEEwavelet.html#contents ) would
normally be the way to go.
A discussion about the technical differences is beyond the scope of
this article but suffice it to say that wavelets deal much better than
MDCT with fast audio transients, say percussion, drums, and sound
effects. Fortunately, since Vorbis is an open-source product, skilled
and open-minded developers can contribute and improve it. Stay tuned!