Re: MELP: 2400 baud speech coding

[jim bell <jimbell@pacifier.com>]

At 01:31 PM 6/4/96 -0700, John Gilmore wrote:
>Mixed-Excitation Linear Predictive encoding gives better speech
>quality than CELP at half the data rate.  Encoding and decoding
>together burn up more than 100% of a TMS320C3x digital signal
>processor at 33MHz -- 64% to encode and 53% to decode.

Does this mean to convert to compressed data AND encrypt, or just converting 
to compressed bits?



>  I don't know
>how it does on a Pentium or an Alpha.  If you have the MIPS at both
>ends, this enables very robust encrypted speech across modem links to
>the Internet. 

I'd rather see thousands of Internet-phone users transmitting at 2400 bps 
than 28.8 kbps...

This is going to add to the telephone companies' woes:  They obviously don't 
want people to have access to nearly-free Internet-LD phone service, but 
their arguments for its regulation will be weaker when it is pointed out 
that the bit rate for compressed, encrypted Internet phone are 2400 bps as 
opposed to 64,000 bps for POTS.

Which raises another question:  When are Internet ISP's going to start 
acting as Internet-phone gateways?  Currently, you can't call somebody on 
POTS with Internet phone.  This would be solved if ISP's could install 
modems and software which did audio-synthesis/digitization on an outbound 
call, driven by the data received on the Internet, and sending the data back 
to the calling end.  Any guesses as to when this will be real?

Jim Bell
jimbell@pacifier.com