[DECtalk] Why are there so many variations of Dec Talk Sound?

GUI Access guiaccess at covad.net
Thu May 31 03:15:01 EDT 2007


>It seems these days I've heard more variations of Dec Talk than I ever did
>in years ago. I know 5.0 is where they messed it up, but it seems that
>various modern implementations sound different than others. Why, for
>instance, does Mobile Speak seem to be the worst, Window-Eyes isn't too bad,
>and other modern products fall somewhere in between? Are device and software
>manufacturers able to, and are, changing the way it sounds? I understood
>there to be 2 different ways Dec Talk sounded, but I believe I have heard
>more variations.


Actually, v4.61 is where "they" messed it up.  I believe that v4.60 
was the last version of DECtalk by D.E.C. before Compaq sold DECtalk 
to Force Computers.  Force is who released v4.61 which in my opinion 
was the worst DECtalk has ever sounded.

Later Fonix (when they acquired the rights to DECtalk) tried to undo 
some of the v4.61 "improvements."

This is where things get weird.  Fonix simultaneously released v5.0 
and v4.63 of DECtalk.  The v4.63 version was an attempt to get as 
close to the D.E.C. version of DECtalk as Fonix could get, given that 
they no longer had the source code to v4.60.

DECtalk v5.0 supposedly sounds more natural by deploying hlsyn (a 
high level parameter synthesizer that translates 13 high level 
parameters to the 39 low level Klatt-style parameters used by all 
earlier versions of DECtalk).

Lastly, Fonix then released DECtalk v4.64 which has a weird "classic 
voices" switch which swaps the nine voices for voices that supposedly 
sound exactly like the D.E.C. voices.

Having played with DECtalk v4.64, I can tell you that neither bank of 
the nine voices sound like the D.E.C. voices of v4.60 and earlier.

I have never heard DECtalk v5.0.  This is supposedly what is in the 
DECtalk USB but comparing the DECtalk USB's DECtalk voices to the 
voices produced by v4.63 of DECtalk yields no noticeable differences 
... and I have a very good ear for these things.

I have no idea what version of DECtalk MobileSpeak uses.  Again, it 
sounds like v4.63 or the DECtalk USB to me.

It'd be great if anyone on the list could expand on the information 
presented here but no one has done so before now, and this topic has 
been discussed at length numerous times over the years.

All of the above are my own observations/findings.

Thanks,

GUI Access




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