[DECtalk] DecTalk newbie

[Jayson Smith]

Hi,
If you use a good audio editor, converting a sound file to a higher sample
rate is not a problem, as these programs have anti-alias filters.  As far as
the 11025 sample rate, that's probably the highest quality DECtalk
generates, period.  I know that a file when played in the Speak43
application sounds no different from the same file converted by the same
application to a .wav file.  Think about it.  Back in the early 1980's when
the DECtalk system was being designed, the technology of today just wasn't
available.  As far as the general public of that time was concerned, when
you bought music, you got it on some form of phonograph records or analog
magnetic tape.  If you wanted to record something and store it in a form
that could be easily played back or erased, you used some form of analog
magnetic tape.  So if the concept of CD-quality sound even existed, it
didn't exist in the minds of the general public as CD"s weren't available
or, if they were, very few people had them.  So back then, a sample rate of
11025 would have probably been perfectly reasonable.  Even now, telephone
systems can't reproduce really high-frequency sound, and I'm sure back in
those days the long-distance telephone networks were even less able to do
so.
Jayson.

----- Original Message -----
From: "Tony Baechler" <tony at baechler.net>
To: "DECtalk Discussions" <dectalk at jaybird.no-ip.info>
Sent: Tuesday, April 19, 2005 10:34 PM
Subject: Re: [DECtalk] DecTalk newbie


> Hi.  I would like to expand on this a little, since I was messing around
> with Jayson's Daisy text file.  Actually, there are two serious problems
> with saving wave files from the demo.  First, 11 KHZ is the max sampling
> rate.  As most people know, that is fairly low quality nowadays.  I would
> say that 22 KHZ is a minimum for decent quality, but of course the only
way
> to get that is by changing the sampling rate which causes problems as
> Jayson describes below.  The other problem is clipping.  That is actually
> what causes the distortion.  The best way to get around this is to save
the
> sample at a lower volume, but I don't think the demo will let you do
> that.  The next best way is to record the speech with something like Sound
> Forge, RecAll, the Windows sound recorder or similar.  The best thing, of
> course, is to record directly from the hardware synth because clipping is
> minimal or nonexistant, but that is more complicated because you need a
> patch cord etc.  So no, there is no way to get it to harmonize with
itself,
> but it isn't that hard if you have decent sound editing software.  Also I
> think there is some natural distortion that is part of the newer
> software.  My DEC Express uses the 4.2CD firmware and doesn't have
> distortion while the software Access 32 versions do, no matter
> what.  Actually I have noticed distortion with most software speech
> synthesizers.
>
> At 07:32 PM 4/19/2005 -0400, you wrote:
> >As far as I know, there is absolutely no way to make DECtalk sing in
harmony
> >with itself without using a wave editor.  DECtalk can only generate one
> >voice at any given instant in time.  There is an option in the DECtalk
demo
> >to save a .wav file of the sound generated by the synthesizer.  Using
that
> >and a sound editor, you could put several of those files together to make
a
> >production, and that's what many people do.  Some, naturally, are of
better
> >quality than others.  Some files have distortion because, presumably, the
> >voices weren't normalized before being combined, and/or the final product
> >wasn't normalized.  Some have aliasing.  Aliasing is a high-frequency
> >element added to a sound, where none was present before.  Aliasing is
caused
> >by people converting the DECtalk wav files to a higher sampling rate
using
> >certain poorly written tools for this purpose.  On the other hand, some
are
> >of probably the best quality possible, given the limits of the DECtalk
> >system itself.
>
>
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