Newsgroups: comp.sys.ti.explorer
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From: jwz@lucid.com (Jamie Zawinski)
Subject: sound format
Message-ID: <JWZ.91Jun4015155@thalidomide.lucid.com>
Sender: usenet@lucid.com
Reply-To: Jamie Zawinski <jwz@lucid.com>
Organization: Lucid, Inc., Menlo Park, CA
X-Windows: You'll envy the dead.
Date: 4 Jun 91 01:51:55

Greetings one and all,

In my continuing quest to convert my Explorer beeps to something my Sparc can
use, I've come across some software that will convert a file of 8-bit 8kHz
samples into Sun's "ulaw" format.  Sounds made-to-order, right?  Well, no.
It wants the samples to be in the range -127 to 128, with 0 (the middle) being
silence.  The Explorer seems thinks of these samples as unsigned 8-bit numbers,
with 0 (the bottom) being silence (if I remember correctly, sampling silence
on an Explorer gets a low-volume 60hz hum of samples between 0 and 50 or so.)

So I tried the obvious conversions: 127-n, n-127, ~n, 127-~n, and so on, and
with the order of bits in n reversed, with little luck.  The samples (of
speech, at least) are just barely legible with 127-n (which sounds a lot like
n & 16, meaning, I guess, that about half the samples are incorrect.)

So I'm pretty confused.  Does anyone know what format the TI D/A chip wants?
Does anyone have any suggestions?  (LGO, are you out there...?)

		-- Jamie