Re: [linux-audio-dev] Simple Plugin API: In/Out Ports

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Subject: Re: [linux-audio-dev] Simple Plugin API: In/Out Ports
From: Bill Gribble (grib_AT_cs.utexas.edu)
Date: ma maalis 06 2000 - 16:38:18 EST


> And even 16 bit integer signal paths with 32 bit integer processing
> is good enough for non-pro signal processing, such as multimedia
> systems, games, arcade game machines and the like.

I think this integer = non-pro, float = pro dichotomy is bogus.

All existing digital audio wire formats (s/pdif, aes/ebu, TDIF, ADAT,
others?) are based on integer sample values. All digital recording
media are based on integer sample values. I see no reason why
floating point values are more useful for pro audio applications, and
a lot of reasons why integer representations are better. For a given
number of bits in your value, a floating-point representation wastes
much of your available information in large and small values that are
far, far beyond the limits of your ultimate destination and will never
be used in real applications.

The phenomenon of linear quantization noise has well-understood
remedies in domains where possible values are evenly-spaced in the
domain of the representation (i.e. integer sample values); I don't
know of any way of meaningfully dithering or otherwise changing the
word-length of floating point values while still doing the right thing
WRT quantization noise.

Floating point makes things easier for the *programmer* (fixed-point
arithmetic is fiendishly hard to code up correctly). Given 32 bits to
work with, and inputs and outputs that will be within a 24-bit range
for the foreseeable future, I'd much rather have a fixed-point
representation than floating point.

Bill Gribble


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