#!/usr/bin/awk -f
#
# Copyright (c) 2009 Ariff Abdullah <ariff@FreeBSD.org>
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
#
# $FreeBSD$
#
# Date: Mon Jul  6 11:03:43 MYT 2009
#   OS: FreeBSD miki.MyBSD.org.my 8.0-CURRENT i386
#

#
# Estimate total number of required FIR taps.
#
# ./kaiser_tools.awk <stopband> <0 - 99>
#                        |         |
#                        |         +-- Bandwidth %
#                        |
#                        +-- stopband attenuation
#

function floor(x, r)
{
        r = int(x);
        if (r > x)
                r--;
        return (r + 0);
}

function kaiser_taps(attn, bw, taps)
{
        taps = 1.0 + (((1.0 * attn) - 7.95) / (14.36 * (1.0 - (bw / 100.0))));
        taps = floor(taps + 0.5);
        taps += 3;
        taps -= taps % 4;
        return (taps);
}

BEGIN {
        if (ARGC < 2)
                ARGV[1] = 160.0;
        if (ARGC < 3)
                ARGV[2] = 95.85;

        printf("Stopband=%.2fdB, Bandwidth=%.2f%%, FIR taps=%d\n",     \
            ARGV[1], ARGV[2], kaiser_taps(ARGV[1], ARGV[2]));
}