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From: hpoppe@bierstadt.scd.ucar.edu (Herb Poppe)
Newsgroups: comp.sys.mac.programmer
Subject: Digital sound techniques
Message-ID: <6226@ncar.ucar.edu>
Date: 6 Feb 90 15:39:21 GMT
References: <1629@ndmath.UUCP> <2850@draken.nada.kth.se>
Sender: news@ncar.ucar.edu
Organization: Scientific Computing Division/NCAR, Boulder, CO
Lines: 39

In article <2850@draken.nada.kth.se> d88-jwa@nada.kth.se (Jon W{tte) writes:
#
#There are two ways of doing twin sampled sound channels.
#Both use several short buffers, like 0.1s each.
#
#Way 1: [deleted]
#
#Way 2: Scientific & Cycle-stealing
#
#Sample the sounds at 11kHz, play them zero-padded at 22kHz:
#i.e. sampled data:
#
#2030 4050 A0B0 C080
#
#would become
#
#2000 3000 4000 5000 A000 B000 C000 8000
#
#which you would then digitally cut-filter at 11KHz and regain the
#previous signal (note: real-time filtering !) This is the method
#used by over-sampling CD players, by the way.
#
#When another sound is needed, you insert the second sound in the
#pad-zeros, so
# [deleted]
#which would then be digitally cut-filtered at 11KHz, played at 22KHz.
#
#This is the method used in digital mixers. If you don't believe me,
#go look it up in nearest DSP book (Digital Signal Processing)
#

1) What is a "cut-filter".

2) How about a specific DSP reference.

--
Herb Poppe      NCAR                         INTERNET: hpoppe@ncar.ucar.edu
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