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From: schooler@inmet.UUCP
Newsgroups: net.audio
Subject: Floating Point CD's
Message-ID: <1753@inmet.UUCP>
Date: Thu, 25-Oct-84 01:04:11 EDT
Article-I.D.: inmet.1753
Posted: Thu Oct 25 01:04:11 1984
Date-Received: Sat, 27-Oct-84 06:17:45 EDT
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Nf-ID: #N:inmet:2600114:000:881
Nf-From: inmet!schooler    Oct 23 10:03:00 1984


	What About Floating Point Representation for CD's?

Currently, a CD waveform sample is represented as a 16-bit integer,
giving a dynamic range of approx. 2^16 = 10^4.8 = 96 dB (roughly).
This integer representation has extremely high (relative) precision
at the upper end of the scale, and low precision at the lower end
of the scale.

Consider a 16-bit floating point representation: say 6 bits of exponent
(base 2) and 10 bits of fraction.  Using the normal implicit-first-bit-
is-1 representation for the fraction, the smallest representable number
is .5, and the largest is 2^63.  The dynamic range is thus 2^64 =
10^19 = 385 dB (roughly).  The precision is .1% of a "dynamic octave".

This sounds like a big win.  Is there something wrong with my math?  Are
there grave difficulties with floating point (or equivalently, logarithmic)
A-D/D-A devices?

			-- Richard Schooler