Re: voice at 14.4 on the Mac

Andrew Green (
Wed, 30 Aug 1995 01:24:33 -0700

>I was wondering if the realaudio algorithm could encode and decode in
>realtime rather than "just" a playback a recorded stream? Probably
>not on a 68030 box:) Might also not fit well in the 14.4 pipe with video.

To my knowledge, the scheme used in Real Audio is CELP, or a close variant.
It takes approx four times real time to process audio on a 120MHz Pentium
-- so it's out of the question for real time use on anything other than a
*fast* workstation. However, CELP is amenable to "tuning" of processing
time used, trading it against quality. 1016 CELP runs at about 4800 bps for
the payload, and even adding in packet headers, leaves quite a bit of space
for additional data, like video.


Andrew Green
Electric Magic Company
209 Downey Street Voice: +1 (415) 759 4100
San Francisco, CA 94117-4421 Fax: +1 (415) 566 6615