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README

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+COPYRIGHT
+
+This package is copyright 2004 by Phil Karn, KA9Q. It may be used
+under the terms of the GNU Lesser General Public License (LGPL). See
+the file "lesser.txt" in this package for license details.
+
+INTRODUCTION
+
+This package provides a set of functions that implement several
+popular forward error correction (FEC) algorithms and several low-level routines
+useful in modems implemented with digital signal processing (DSP).
+
+The following routines are provided:
+
+1. Viterbi decoders for the following convolutional codes:
+
+r=1/2 k=7 ("Voyager" code, now a widely used industry standard)
+r=1/2 k=9 (Used on the IS-95 CDMA forward link)
+r=1/6 k=15 ("Cassini" code, used by several NASA/JPL deep space missions)
+
+2. Reed-Solomon encoders and decoders for any user-specified code.
+
+3. Optimized encoder and decoder for the CCSDS-standard (255,223)
+Reed-Solomon code, with and without the CCSDS-standard "dual basis"
+symbol representation.
+
+4. Compute dot product between a 16-bit buffer and a set of 16-bit
+coefficients. This is the basic DSP primitive for digital filtering
+and correlation.
+
+4. Compute sum of squares of a buffer of 16-bit signed integers. This is
+useful in DSP for finding the total energy in a signal.
+
+5. Find peak value in a buffer of 16-bit signed integers, useful for
+scaling a signal to prevent overflow.
+
+SIMD SUPPORT
+
+This package automatically makes use of various SIMD (Single
+Instruction stream, Multiple Data stream) instruction sets, when
+available: MMX, SSE and SSE2 on the IA-32 (Intel) architecture, and
+Altivec on the PowerPC G4 and G5 used by Power Macintoshes.
+
+"Altivec" is a Motorola trademark; Apple calls it "Velocity Engine",
+and IBM calls it "VMX". Altivec is roughly comparable to SSE2 on the
+IA-32.
+
+Many of the SIMD versions run more than an order of
+magnitude faster than their portable C versions. The available SIMD
+instruction sets, if any, are determined at run time and the proper
+version of each routine is automatically selected. If no SIMD
+instructions are available, the portable C version is invoked by
+default. On targets other than IA-32 and PPC, only the portable C
+version is built.
+
+The SIMD-assisted versions generally produce the same results as the C
+versions, with a few minor exceptions. The Viterbi decoders in C have
+a very slightly greater Eb/No performance due to their use of 32-bit
+path metrics. On the other hand, the SIMD versions use the
+"saturating" arithmetic available in these instructions to avoid the
+integer wraparounds that can occur in C when argument ranges are not
+properly constrained. This applies primarily to the "dotprod" (dot
+product) function.
+
+The MMX (MultiMedia eXtensions) instruction set was introduced on
+later Pentium CPUs; it is also implemented on the Pentium II and most
+AMD CPUs starting with the K6. SSE (SIMD Streaming Extensions) was
+introduced in the Pentium III; AMD calls it "3D Now! Professional".
+Intel introduced SSE2 on the Pentium 4, and it has been picked up by
+later AMD CPUs. SSE support implies MMX support, while SSE2 support
+implies both SSE and MMX support.
+
+The latest IA-32 SIMD instruction set, SSE3 (also known as "Prescott
+New Instructions") was introduced in early 2004 with the latest
+("Prescott") revision of the Pentium 4. Relatively little was
+introduced with SSE3, and this library currently makes no use of it.
+
+See the various manual pages for details on how to use the library
+routines.
+
+Copyright 2004, Phil Karn, KA9Q
+karn@ka9q.net
+http://people.qualcomm.com/karn
+
+This software may be used under the terms of the GNU Lesser General
+Public License (LGPL); see the file lesser.txt for details.
+
+Revision history:
+Version 1.0 released 29 May 2001
+
+Version 2.0 released 3 Dec 2001:
+Restructured to add support for shared libraries.
+
+Version 2.0.1 released 8 Dec 2001:
+Includes autoconf/configure script
+
+Version 2.0.2 released 4 Feb 2002:
+Add SIMD version override options
+Test for lack of SSE2 mnemonic support in 'as'
+Build only selected version
+
+Version 2.0.3 released 6 Feb 2002:
+Fix to parityb function in parity.h
+
+feclib version 1.0 released November 2003
+Merged SIMD-Viterbi, RS and DSP libraries
+Changed SIMD Viterbi decoder to detect SSE2/SSE/MMX at runtime rather than build time
+
+feclib version 2.0 (unreleased) Mar 2004
+General speedups and cleanups
+Switch from 4 to 8-bit input symbols on all Viterbi decoders
+Support for Altivec on PowerPC
+Support for k=15 r=1/6 Cassini/Mars Pathfinder/Mars Exploration Rover/STEREO code
+Changed license to GNU Lesser General Public License (LGPL)