USR Sportster Voice 33.6 problems...

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On Tue, 3 Feb 1998, Martin Fick wrote:

> Others mentioned that I should try to set the 
> 
>  rec_compression 4
> 
> that seemed to allow me to convert the file format.

I tried that, but it didn't seem to make much difference (see below) and
what's more, it caused the sound quality of the recording to become very
poor.

While the GSM format seems to produce excellent quality sound, when I
tried ADPCM recording and playback through the modem, the sound has some
kind of strange distortion, which is hard to describe. It sounds kind of
like a the voice is affected by a low buzzing or warbling sound.

But since it seems it's only me that has this problem, it must be caused
by something else. Has anyone else tried the vgetty package on a 68k
machine?

Here's some more details about the sound format conversion problem:

Converting ADPCM to or from BASIC or AU formats results in incredible
crackling and hissing noise, with the original sound barely noticable over
all the noise. I.e. there definitely is some hint of the original sound,
but it's incredibly distorted and almost completely covered up by all the
noise. This problem reminds me of what you get when playing a signed
sample as unsigned and vice versa, but since I've tried reversing the
signed/unsigned-ness of the sound without success I figure this is not the
problem.

Converting from ADPCM to BASIC or AU and then back to ADPCM works fine,
the resultant file sounds exactly as it should.

Conversion from BASIC or AU to ADPCM then back to BASIC or AU often works
fairly well, but there are odd clicks in the sound. But on some files this
doesn't work at all, all you get is noise with the sound barely noticable 
over all the distortion. This seems to be related to whether the sound is
stored in signed or unsigned format, except I can't remember which of the
two works and which doesn't. This is, of course, understandable, but I'm
sure the odd clicks in the sound are not normal.

All conversions involving GSM just produce noise.

Is there someone who has a USR Sportster 33.6 voice fax modem who could
exchange some recordings with me, in order to help determine what is
causing these problems?

About the other problems I was experiencing, the handset problem turns out
to be a fault not caused by vgetty, but rather a problem with the modem.
So once I get this sound format problem sorted out everything will be
going nicely.

-- 
Mario Becroft    Auckland, New Zealand
mb@tos.pl.net    http://www.pl.net/~mario/ |\__/,| (`\
Tariland, Atari Support in New Zealand    _.|o o |_ ) )
tariland@tos.pl.net  http://www.pl.net/~mario/tariland/ --(((---(((--------

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