Choosing the Right Codec
October 13, 2000
Choosing the Right Codec
Based on a detailed study of RealNetworks' documentation and some practical
experience, I recommend the following if you want to stream audio without
problems. In each case, if there's a reasonable alternative for better
frequency response and quality, I list it second ... compatibility always
comes first! (Note: RA3 means the RealAudio Player Version 3, etc.). Some
of these codecs have different names (indicated where known) and may or may
not be available, depending on whether you're using Sound Forge or a
RealAudio Encoder or the new RealProducer program.
For absolute minimum bandwidth requirements (14.4 Kbps modems):
- Voice: 8 Kbps Voice (supported by every RealPlayer ever
released) or 8.5 Kbps Voice (compatible only back to RA4, but
higher quality)
- Music: 12 Kbps Music
For typical bandwidth requirements (28.8 to 33.6 Kbps modems):
- Voice: 15.2 Kbps Voice (doesn't have the ultimate bandwidth,
but it's compatible way back to RA2) or 16 Kbps Voice-Mono (much
better response, but you'll need RA5 or later to play it)
- Music: 16 Kbps Music-Mono High (yes, it's mono, but you get
5.5 KHz of response and compatibility back to RA3. If you want stereo, use
20 Kbps Music-Stereo, but you'll go down to 4 KHz...trust me, it's
not worth it). If they have a pristine 33.6 Kbps connection and RA4 (or
higher), you could also try 32 Kbps Music for 5.5 KHz in stereo mode
or a whopping 8 KHz in mono.
Stealth MP3?
Now, if you're willing to let them download first and play later, or if they
have ISDN or better, these are some good things to look at:
40 Kbps Music (aka ISDN), which is backwards compatible back
to RA3, gives you 8 KHz in stereo or 11 KHz in mono, and sounds pretty good
for the file sizes you'll get.
80 Kbps Music (aka Dual ISDN), also RA3 compatible, for 16 KHz
stereo or 20 KHz mono. This is probably the highest setting you should ever
use.
Here's a song written and performed by my 4-year-old son, using some of the
above schemes:
The absolute top performer is 96 Kbps Music-G2 Stereo, which gives a
blistering 24 KHz audio response but is playable only on the newest G2
player. In testing, I've found this format to sound virtually
indistinguishable from MP3 on much pop music material, while taking 1/3
as much time to encode as MP3 and about half the disk/download space ...
and 80 Kbps Music - Stereo is pretty close. Why MP3 gets all the
publicity, I'll never know! There are far more people with RealAudio players
than MP3 players. Give it a shot.
Code, Code, Code Your Sound / And You'll Make It Stream...
The WebDeveloper.com Secret Guide to RealAudio
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