🚀 go-pugleaf

(Something is eating about 50% of my posts.  I *think* this one never
made it out--please forgive me if you've seen it before.)

I received a few responses to my "What is RELP" query.  RELP stands
for residually excited (or encoded, maybe) linear predictive code.
The strain I've been hearing about digitizes voice at 9600 bps.

I would have responded sooner but I lost one of the replies and spent
some time looking for it.

My need to know is this: The folks who are responsible for the
space-to-ground link for Space Station Freedom are currently planning
to use RELP to get two full duplex voice links at 9600 bps each per
direction.  I work on the SSF internal audio distribution and need to
know how this affects our design.

So, does anybody have any RELP code for sale or to be given away?

+++++ Summary of responses +++++

The most complete discussion received to date and that I haven't
managed to lose is from John Adcock at Lockheed Sanders.

>From: adcock@rocket.sanders.com (john adcock)
>
>Yes that's what it stands for.
>
>Normal lpc vocoding uses only the all pole model of the
>spectrum and the pitch to reconstruct the speech.  That is to
>say that during synthesis in a vanilla lpc vocoder the excitation 
>to the all pole filter is synthesized.  RELP preserves the excitation
>by saving the residual.  That is with RELP you estimate 
>the pole model, then you do a zero filter with your pole model and preserve 
>the "residual" that you are left with.  The residual is then used 
>to reconstruct the speech later.
>
>I've heard more about CELP
>(Code excited linear predictive coding) which is 
>(as far as I know) based on the same idea but uses a 
>vector quantization method to code the residual instead of
>actually transmitting the residual itself.  Whether or not
>a RELP or CELP vocoder is 9600 bps depends entirely on the 
>implementation.
>NSA has a standard for the CELP algorithm and a 9600 baud
>implementation.

+++++++++++
>From: Rich Kerr <RJK@MILAN.QUALCOMM.COM>
>
>Try ICCASP 84,85. Presenter is PHil Wilson, Linkabit.
>
>Also PHD Thesis, Imperial University, London, Phil Wilson, 1982. RELP
>
++++++++++

I also received a message from Tony Robinson
(ajr@engineering.cambridge.ac.uk) referring me to books by Rabiner and
Schafer and Jayant and Noll, but I had already gotten all I could get
on the subject from those books.  Thanks anyway.

++++++++++

Many thanks to all who responded.

--
J. Porter Clark    jpc@avdms8.msfc.nasa.gov