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The GUS Programmer's Digest Thursday, 11 May 1995 Volume 19 : Number 004
Today's Topics:
Hi out there?
Standard Info:
- Meta-info about the GUS can be found at the end of the Digest.
- Before you ask a question, please READ THE FAQ.
----------------------------------------------------------------------
From: Chris James <JAMESC@mail.medoto.unimelb.edu.au>
Date: Thu, 11 May 1995 09:55:00 -0700 (PDT)
Subject: Hi out there?
Just wondered whether this mail group was read by anyone else?
If it is then any opinions on these thoughts/experiences:
Just got the V2.22 Gravis SDK, not much to say except that presumably _some_
problems are fixed (like the notable absence of documentation for some
functions).
For those that program the MAX and use C++ 9 (and I mean really write C++),
you
presumably have fixed a couple of header files for the codec support. I
found they
missed out the ending brackets for the extern "C" declarations (only noticed
when
you do a C++ compile) again. (The .h's are identical so I just use the old
ones I fixed).
Has anyone used the MAX's recording gain in Windows? That's the separate
slider which
is gain applied after the input to the recording multiplexer. I found that I
start to get a
significant DC offset in the signal when I use this. This also has happened
when I've
programmed the codec using the SDK in DOS, in the end I left out this gain
control which
is a bit of a shame. Having read the Codec data sheet I find there's a
couple of things that
could account for this problem. Firstly the codec is able to do some
autocalibration which
might just be designed to sort out DC problems amoungst other things. This
calibration is
done when one switches mode on the codec, which is for example between some
coding
options (say 16-bit PCM to ADPCM). It is possible to disable/enable this. So
maybe its
not enabled by the software. Even if it was this doesn't help if we only
adjust the input gain,
so it would be good to be able to force a re-calibrate before commencing
recording in any
event. I may have misunderstood what re-calibrate means in this case. The
other possibility is that there is just some inherent DC generated inside
the codec (all the gains are internal to the chip). If
this is so then maybe it would be nice if we could activate the codec's
digital high-pass filters, thus
getting rid of any DC at all. Really these should be switched on all the
time since this is a "sound" card we're talking about, not for general
acquisition. Yet another option with the codec! Incidentally the codec can
also manage full duplex on _one_ DMA channel! This may not be possible with
the circuit set up on the MAX, in any case its not an option in the SDK.
I would like to follow Gravis/Forte's advice and do some of my own level
programming. This
won't fix the Window's problem (unless I write a Windows driver, ughh! In my
dreams) and in
any case there's only so many days in a life. Otherwise the SDK is brill! My
only other comment is, has anyone actually managed to get click free
continuous (i.e. DD) output from the GF1 using the SDK? Following up Future
Crew's hints on this is another project in my long list...
Has anyone tried out these V4.11 drivers etc yet?
yours, hopefully not mailing into a void
Chris James
------------------------------
End of The GUS Programmer's Digest V19 #4
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