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2020/giles/Makefile
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#!/usr/bin/env make
#
# 2020 makefile
#
# This work by Landon Curt Noll, Simon Cooper, and Leonid A. Broukhis
# is licensed under:
#
# Creative Commons Attribution-ShareAlike 3.0 Unported License.
#
# See: http://creativecommons.org/licenses/by-sa/3.0/
#############################
# shell used by this Makefile
#############################
#
SHELL= /bin/bash
#######################
# common tool locations
#######################
#
A2P= a2p
AR= ar
ASA= asa
AT= at
ATQ= atq
ATRM= atrm
AWK= awk
BANNER= banner
BASE64= base64
BASENAME= basename
BATCH= batch
BC= bc
BINHEX= binhex
BISON= bison
BUNZIP2= bunzip2
BZCAT= bzcat
BZCMP= bzcmp
BZDIFF= bzdiff
BZEGREP= bzegrep
BZFGREP= bzfgrep
BZGREP= bzgrep
BZIP2= bzip2
BZLESS= bzless
BZMORE= bzmore
C2PH= c2ph
C89= c89
C99= c99
CAL= cal
CALC= calc
CAT= cat
CD= cd
CHFLAGS= chflags
CHGRP= chgrp
CHMOD= chmod
CKSUM= cksum
CLANG= clang
CLANG_PLUSPLUS= clang++
CLEAR= clear
CMP= cmp
COL= col
COLLDEF= colldef
COLRM= colrm
COLUMN= column
COMPRESS= compress
CP= cp
CPIO= cpio
CPP= cpp
CRC32= crc32
CSH= csh
CSPLIT= csplit
CURL= curl
CUT= cut
C_PLUSPLUS= c++
C_PLUSPLUS_FILT= c++filt
DATE= date
DC= dc
DD= dd
DF= df
DIFF3= diff3
DIFF= diff
DIG= dig
DIRNAME= dirname
ECHO= echo
ED= ed
EGREP= egrep
ENV= env
EQN= eqn
ETAGS= etags
EXPECT= expect
EXPR= expr
FALSE= false
FGREP= fgrep
FILE= file
FIND2PERL= find2perl
FIND= find
FLEX= flex
FLEX_PLUSPLUS= flex++
FMT= fmt
FOLD= fold
FS_USAGE= fs_usage
FUNZIP= funzip
FUSER= fuser
GCC= gcc
GDIFFMK= gdiffmk
GENCAT= gencat
GENSTRINGS= genstrings
GETOPT= getopt
GETOPTS= getopts
GINDENT= gindent
GNUMAKE= gnumake
GREP= grep
GROFF= groff
GROFFER= groffer
GROG= grog
GROPS= grops
GROTTY= grotty
GUNZIP= gunzip
GVIM= gvim
GZCAT= gzcat
GZEXE= gzexe
GZIP_PROG= gzip
G_PLUSPLUS= g++
H2PH= h2ph
H2XS= h2xs
HASH= hash
HEAD= head
HOSTNAME_PROG= hostname
ICONV= iconv
ID= id
INDENT= indent
INFO= info
JOT= jot
KILL= kill
KSH= ksh
LAST= last
LD= ld
LESSECHO= lessecho
LEX= len
LINK= link
LN= ln
LS= ls
M4= m4
MAKE= make
MAN= man
MKDIR= mkdir
MKFIFo= mkfifo
MKTEMP= mktemp
MV= mv
NANO= nano
NASM= nasm
NEQN= neqn
NICE= nice
NL= nl
NM= nm
NOHUP= nohup
NROFF= nroff
NSLOOKUP= nslookup
OD= od
OPENSSL= openssl
PASTE= paste
PATCH= patch
PATHCHK= pathchk
PAX= pax
PERL= perl
PICO= pico
PR= pr
PRINTENV= printenv
PS= ps
PTAR= ptar
PTARDIFF= ptardiff
PTARGREP= ptargrep
PWD= pwd
PYDOC= pydoc
PYTHON= python
PYTHONW= pythonw
READLINK= readlink
RENICE= renice
RESET= reset
REV= rev
RI= ri
RM= rm
RMDIR= rmdir
RSYNC= rsync
RUBY= ruby
RVIM= rvim
SAY= say
SCP= scp
SCREEN= screen
SCRIPT= script
SDIFF= sdiff
SED= sed
SEQ= seq
SFTP= sftp
SH= sh
SHA1= sha1
SHA= sha
SHAR= shar
SHASUM5_18= shasum5.18
SHASUM= shasum
SIZE= size
SLEEP= sleep
SORT= sort
SSH= ssh
STAT= stat
STRIP= strip
STTY= stty
SUM= sum
SYNC= sync
TABS= tabs
TAIL= tail
TAR= tar
TEE= tee
TEST= test
TFTP= tftp
TIDY= tidy
TIME= time
TOP= top
TOUCH= touch
TPUT= tout
TPUT= tput
TR= tr
TROFF= troff
TRUE= true
TSET= tset
TSORT= tsort
UL= ul
UNAME= uname
UNCOMPRESS= uncompress
UNEXPAND= unexpand
UNIFDEF= unifdef
UNIFDEFALL= unifdefall
UNIQ= uniq
UNITS= units
UNLINK= unlink
UNZIP= unzip
UNZIPSFX= unzipsfx
UPTIME= uptime
UUDECODE= uudecode
UUENCODE= uuencode
UUIDGEN= uuidgen
VI= vi
VIEW= view
VIM= vim
VIMDIFF= vimdiff
W= w
WAIT4PATH= wait4path
WAIT= wait
WC= wc
WHAT= what
WHATIS= whatis
WHICH= which
WHO= who
WHOAMI= whoami
WHOIS= whois
WRTIE= write
XAR= xar
XARGS= xargs
XATTR= xattr
XXD= xxd
YACC= yacc
YES= yes
ZCAT= zcat
ZCMP= zcmp
ZDIFF= zdiff
ZEGREP= zegrep
ZFGREP= zfgrep
ZFORCE= zforce
ZGREP= zgrep
ZIP= zip
ZIPCLOAK= zipcloak
ZIPGREp= zipgrep
ZIPINFo= zipinfo
ZIPNOTE= zipnote
ZIPSPLIT= zipsplit
ZLESS= zless
ZMORE= zmore
ZNEW= znew
ZPRINT= zprint
ZSH= zsh
# Set X11_LIBDIR to the directory where the X11 library resides
#
#X11_LIBDIR= /usr/X11R6/lib
#X11_LIBDIR= /usr/X11/lib
X11_LIBDIR= /opt/X11/lib
# Set X11_INCLUDEDIR to the directory where the X11 include files reside
#
#X11_INCDIR= /usr/X11R6/include
#X11_INCDIR= /usr/X11/include
X11_INCDIR= /opt/X11/include
# CWARN - Silence warnings that ${CWARN} would normally complain about
# CSILENCE -Compiler warnings
#
ifeq ($(CC),clang)
# clang CSILENCE and CWARN
#
#CSILENCE=
#CSILENCE= -Wno-implicit-int
CSILENCE= -Wno-disabled-macro-expansion -Wno-empty-body -Wno-float-conversion -Wno-float-equal \
-Wno-missing-variable-declarations -Wno-shadow -Wno-shorten-64-to-32 -Wno-sign-conversion \
-Wno-string-plus-char -Wno-string-plus-int -Wno-unknown-warning-option
#
#CWARN= $CSILENCE}
#CWARN= -Wall $CSILENCE}
#CWARN= -Wall -Wextra $CSILENCE}
#CWARN= -Wall -Wextra -pedantic ${CSILENCE}
#CWARN= -Wall -Wextra -Weverything $CSILENCE}
CWARN= -Wall -Wextra -Weverything -pedantic ${CSILENCE}
else
ifeq ($(CC),gcc)
# gcc CSILENCE and CWARN
#
#CSILENCE=
#CSILENCE= -Wno-implicit-int
CSILENCE= -Wno-empty-body -Wno-string-plus-char -Wno-string-plus-int -Wno-unknown-warning-option
#
#CWARN= $CSILENCE}
#CWARN= -Wall $CSILENCE}
#CWARN= -Wall -Wextra $CSILENCE}
CWARN= -Wall -Wextra -pedantic ${CSILENCE}
else
# default CSILENCE and WARN
#
#CSILENCE=
#CSILENCE= -Wno-implicit-int
CSILENCE= -Wno-empty-body -Wno-string-plus-char -Wno-string-plus-int -Wno-unknown-warning-option
#
#CWARN= $CSILENCE}
#CWARN= -Wall $CSILENCE}
#CWARN= -Wall -Wextra $CSILENCE}
CWARN= -Wall -Wextra -pedantic ${CSILENCE}
#CWARN= -Wall -Wextra -Weverything $CSILENCE}
#CWARN= -Wall -Wextra -Weverything -pedantic ${CSILENCE}
endif
endif
# compiler standard
#
#CSTD=
#CSTD= -ansi
#CSTD= -std=c11
CSTD= -std=c99
# compiler bit architecture
#
# Some entries require 32-bitness:
# ARCH= -m32
#
# Some entries require 64-bitness:
# ARCH= -m64
#
# By default we assume nothing:
#
ARCH=
# defines that are needed to compile
#
CDEFINE=
#CDEFINE= -DIOCCC
# include files that are needed to compile
#
CINCLUDE=
#CINCLUDE= -include stdlib.h
#CINCLUDE= -include stdio.h
#CINCLUDE= -include stdlib.h -include stdio.h
#CINCLUDE= -I ${X11_INCDIR}
# optimization
#
# Most compiles will safely use -O2. Some can use only -O1 or -O.
# A few compilers have broken optimizers or this entry make break
# under those buggy optimizers and thus you may not want anything.
# Reasonable compilers will allow for -O3.
#
#OPT=
#OPT= -O
#OPT= -O1
#OPT= -O2
OPT= -O3
# default flags for ANSI C compilation
#
CFLAGS= ${CSTD} ${CWARN} ${ARCH} ${CDEFINE} ${CINCLUDE} ${OPT}
# Libraries needed to build
#
LIBS=
#LIBS= -L ${X11_LIBDIR}
# ANSI compiler
#
# Set CC to the name of your ANSI compiler.
#
# Some entries seem to need gcc. If you have gcc, set
# both CC and MAY_NEED_GCC to gcc.
#
# If you do not have gcc, set CC to the name of your ANSI compiler, and
# set MAY_NEED_GCC to either ${CC} (and hope for the best) or to just :
# to disable such programs.
#
CC= cc
#CC= clang
MAY_NEED_GCC= gcc
##############################
# Special flags for this entry
##############################
#
OBJ= prog.o
DATA= dtmf.bin pi.wav
TARGET= prog
#
ALT_OBJ=
ALT_TARGET=
#################
# build the entry
#################
#
all: ${TARGET} ${DATA}
@${TRUE}
prog: prog.c
${CC} ${CFLAGS} $< -o $@ ${LIBS}
# alternative executable
#
alt: ${ALT_TARGET}
@${TRUE}
# data files
#
data: ${DATA}
@${TRUE}
###############
# utility rules
###############
#
everything: all alt
clean:
${RM} -f ${OBJ} ${ALT_OBJ}
@-if [ -f indent.c ]; then \
${ECHO} ${RM} -f indent.c; \
${RM} -f indent.c; \
fi
clobber: clean
${RM} -f ${TARGET} ${ALT_TARGET}
@-if [ -e sandwich ]; then \
${RM} -f sandwich; \
${ECHO} 'ate sandwich'; \
fi
nuke: clobber
@${TRUE}
dist_clean: nuke
@${TRUE}
install:
@${ECHO} "Surely you are performing, Dr. Science!"
@${TRUE}
# backwards compatibility
#
build: all
@${TRUE}
# you may be able to mis-understand the source by reading indent.c
#
indent.c: prog.c
@if which "${GINDENT}" >/dev/null 2>&1; then \
${ECHO} ${RM} -f $@; \
${RM} -f $@; \
${ECHO} "${GINDENT} < $< > $@"; \
${GINDENT} < $< > $@; \
elif which "${INDENT}" >/dev/null 2>&1; then \
${ECHO} ${RM} -f $@; \
${RM} -f $@; \
${ECHO} "${INDENT} < $< > $@"; \
${INDENT} < $< > $@; \
else \
${ECHO} "no intent prog found, ident $< yourself, sorry"; \
${ECHO} "exit 1"; \
exit 1; \
fi
##################
# 133t hacker rulz
##################
#
love:
@${ECHO} 'not war?'
@${TRUE}
haste:
$(MAKE) waste
@${TRUE}
waste:
@${ECHO} 'haste'
@${TRUE}
make:
@${ECHO} 'We encourage you to attend a maker faire'
@${TRUE}
easter_egg:
@${ECHO} you expected to often mis-understand this $${RANDOM} magic
@${ECHO} chongo '<was here>' "/\\oo/\\"
@${ECHO} Eggy and Kitty
fabricate fashion form frame manufacture produce: make
@${TRUE}
sandwich:
@if [ `id -u` -eq 0 ]; then \
${ECHO} 'Okay.'; \
${ECHO} $${RANDOM}`date +%s`$${RANDOM} | \
${SHASUM} -a 512256 | \
${SED} -e 's/ .*//' > $@; \
else \
${ECHO} 'Reall?!? Make it yourself.'; \
exit 1; \
fi
# Understand the history of the Homebrew Computer Club
# as well as the West Coast Computer Faire and
# you might be confused different. :-)
#
supernova: nuke
@-if [ -r .code_anal ]; then \
${RM} -f .code_anal_v6; \
else \
${ECHO} "planet deniers, like a few silly IAU members, are so cute when they try to defend their logic"; \
fi
@${ECHO} A $@ helps ${MAKE} the elements that help form planets
@${TRUE}
deep_magic:
@-if [ -r .code_anal ]; then \
ccode_analysis --deep_magic 253d8c80830e2df66c018820004b3d4939821bbd7d781fc50d9e633797e44f65d1d62c707bb7e5a82c328a37bbf9ecb4c46fb56aa3f08641fcf45d10ba3c6081 --FNV1a_hash_512_bit "prog"; \
else \
${ECHO} "Wrong! Do it again!"; \
sleep 1; \
${ECHO} "Wrong! Do it again!"; \
sleep 1; \
${ECHO} "Wrong! Do it again!"; \
fi
@${TRUE}
magic: deep_magic
@-if [ -r .code_anal ]; then \
ccode_analysis --level 391581 --mode 216193 --state Riesel --FNV1a_hash_512_bit "prog"; \
else \
${ECHO} "If you don't eat yer meat, you can't have any pudding!"; \
${ECHO} "How can you have any pudding if you don't eat yer meat?!"; \
${ECHO} "p.s. Be cafeful with that axe, Eugene."; \
fi
@${TRUE}
# The IOCCC resident astronomer states
#
charon: supernova
@${ECHO} $@ is a dwarf planet
@${ECHO} dwarf is a type of planet
@${ECHO} therefore we continue to tell the IAU that $@ is a planet
pluto: supernova
${MAKE} charon
@${ECHO} $@ is a dwarf planet
@${ECHO} dwarf is a type of planet
@${ECHO} therefore, $@ is a planet
@${ECHO} having lots of planets is good feature because $< can help ${MAKE} a lot of them
2020/giles/dtmf.bin
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# Most phony
Edward Giles
<https://id523a.com/>
The code for this entry can be found in prog.c
## Judges' comments:
### To use:
make
./prog
### Try:
./prog < pi.wav
# [https://en.wikipedia.org/wiki/867-5309/Jenny]
./prog 867-5309 > jenny.wav
# Use an audio player to play jenny.wav
### Selected Judges Remarks:
A cross platform utility for both encoding and decoding tones.
## Author's comments:
### Introduction and Usage
This program encodes and decodes [dual-tone multiple frequency](https://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling) signals used in telephone systems, more commonly known as Touch-Tones.
If the program is executed with no arguments, it will read a WAV file from standard input, decode the touch-tones in the file, and output the corresponding digits to standard output. This program only supports WAV files that have exactly 16 bits per sample, but it allows any sample rate and any number of audio channels.
$ ./prog < pi.wav
31415926
If the program is executed with a command-line argument, it will generate the tones corresponding to the specified characters, writing them to standard output as a WAV file.
$ ./prog 867-5309 | aplay
### Interesting Features
* When compiled with `gcc -pedantic -Wall -Wextra` there are no compiler warnings.
* This program can be successfully compiled and run on Windows, using both Microsoft's C compiler and [TCC](https://bellard.org/tcc/).
* This program resamples the incoming audio, so that it can accept audio data at any sample rate.
* The code that generates the output sine-waves is the same as the code that looks for sine-waves in the input. (see Algorithm Details for roughly how this works)
* Despite handling lots of sine waves, the program only uses basic arithmetic operations. It does not depend on `libm`.
* All type punning is done with `memcpy` so there are no strict-aliasing violations.
* The size of the source code using the IOCCC size tool is 1963, the year the first push-button telephones were made available to customers.
* The source code is roughly in the shape of a telephone handset.
### Assumptions
* Code is compiled using the C99 or C11 standard
* `CHAR_BIT == 8`
* Machine is little-endian
* `int16_t`, `uint16_t`, and `uint32_t` exist
* `int16_t` is 2's-complement
* `double` is an IEEE 754 binary64 floating-point type
* `sizeof(double) == 8`
### Obfuscations
* DSP code is inherently somewhat difficult to understand.
* Lots of identifier reuse. Each identifier is used for about 2.2 different tasks, on average.
For example, `aa` is both a variable and a macro for error handling,
and `memcpy` is both a library function and a goto-label.
* Most of the identifiers are only 1 or 2 characters long, and are unrelated to their actual function.
* The `f` macro is used to unroll some of the loops.
* Some numerical constants are replaced with character literals, so the actual value is unclear.
* All of the strings used by the program have been combined into a single string literal.
* Most of the values used for the actual signal-processing all reside in one array, named `l`. This array is usually accessed at index `z` plus a constant. Accesses of this type have been rewritten from, e.g. `l[z+17]` to `17[l+z]`. `[l+z]` ends up occurring quite often, so I created the macro `a` as a shorthand.
### Algorithm Details
Each tone in a DTMF signal is a combination of two frequencies. The lower frequency determines which row the digit is in, and the higher frequency determines the column. There are 4 possible row frequencies and 4 possible column frequencies.
| | **1209 Hz** | **1336 Hz** | **1477 Hz** | **1633 Hz** |
|------------|-------------|-------------|-------------|-------------|
| **697 Hz** | 1 | 2 abc | 3 def | A |
| **770 Hz** | 4 ghi | 5 jkl | 6 mno | B |
| **852 Hz** | 7 pqrs | 8 tuv | 9 wxyz | C |
| **941 Hz** | * | 0 | # | D |
This program determines which frequencies are present in the input by passing it through a set of 8 virtual resonators, each tuned to one of the frequencies used for DTMF. These can be implemented using only basic arithmetic, and they are able to 'select' a specific frequency from the input sound, blocking all other frequencies from reaching the output. The loudness of the sound output from each resonator can therefore be used as a measure of how much of a particular frequency was present in the input. The program then decides, over the course of one tone, which row frequency and which column frequency were most prominent.
Tones are generated using those same resonators by providing [an impulse](https://en.wikipedia.org/wiki/Kronecker_delta#Digital_signal_processing) as input. An impulse can be thought of as consisting of sine-waves at all frequencies, and when it is put through one of the resonators, the result is a single pure sine wave.
-----------------------------------------------------------------------------------------------------
(c) Copyright 1984-2020, [Leo Broukhis, Simon Cooper, Landon Curt Noll][judges] - All rights reserved
This work is licensed under a [Creative Commons Attribution-ShareAlike 3.0 Unported License][cc].
[judges]: http://www.ioccc.org/judges.html
[cc]: http://creativecommons.org/licenses/by-sa/3.0/
-----------------------------------------------------------------------------------------------------
2020/giles/index.html
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<!doctype html public "-//W3C//DTD HTML 4.0 Transitional //EN">
<html>
<head>
<meta name="GENERATOR" content="mkd2html 2.2.2">
<meta http-equiv="Content-Type"
content="text/html; charset=utf-8"> <link rel="stylesheet"
type="text/css"
href="../hint.css" />
<title></title>
<title>Most phony</title>
</head>
<body>
<CENTER>
<IMG SRC="/png/ioccc.png" ALT="IOCCC" height=78 width=267>
<P><FONT size="6"><I>The International Obfuscated C Code Contest</I></FONT></P>
<div id="bar">
<ul>
<li><a href="../index.html">About the 27th IOCCC</a></li>
<li><a href="../whowon.html">27th IOCCC Winners</a></li>
<li><a href="/index.html">IOCCC home</a></li>
<li><a href="/winners.html">List of All Winners</a></li>
<li><a href="/judges.html">The Judges</a></li>
</ul>
</div>
<P><FONT size="6"><B>A 27<sup>th</sup> IOCCC Winner</B></FONT></P>
</CENTER>
<h1>Most phony</h1>
<p>Edward Giles<br/>
<a href="https://id523a.com/">https://id523a.com/</a></p>
<p>The code for this entry can be found in <a href="prog.c">prog.c</a></p>
<h2>Judges' comments:</h2>
<h3>To use:</h3>
<pre><code>make
./prog
</code></pre>
<h3>Try:</h3>
<pre><code>./prog &lt; pi.wav
# [https://en.wikipedia.org/wiki/867-5309/Jenny]
./prog 867-5309 &gt; jenny.wav
# Use an audio player to play jenny.wav
</code></pre>
<h3>Selected Judges Remarks:</h3>
<p>A cross platform utility for both encoding and decoding tones.</p>
<h2>Author&rsquo;s comments:</h2>
<h3>Introduction and Usage</h3>
<p>This program encodes and decodes <a href="https://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling">dual-tone multiple frequency</a> signals used in telephone systems, more commonly known as Touch-Tones.</p>
<p>If the program is executed with no arguments, it will read a WAV file from standard input, decode the touch-tones in the file, and output the corresponding digits to standard output. This program only supports WAV files that have exactly 16 bits per sample, but it allows any sample rate and any number of audio channels.</p>
<pre><code>$ ./prog &lt; pi.wav
31415926
</code></pre>
<p>If the program is executed with a command-line argument, it will generate the tones corresponding to the specified characters, writing them to standard output as a WAV file.</p>
<pre><code>$ ./prog 867-5309 | aplay
</code></pre>
<h3>Interesting Features</h3>
<ul>
<li>When compiled with <code>gcc -pedantic -Wall -Wextra</code> there are no compiler warnings.</li>
<li>This program can be successfully compiled and run on Windows, using both Microsoft&rsquo;s C compiler and <a href="https://bellard.org/tcc/">TCC</a>.</li>
<li>This program resamples the incoming audio, so that it can accept audio data at any sample rate.</li>
<li>The code that generates the output sine-waves is the same as the code that looks for sine-waves in the input. (see Algorithm Details for roughly how this works)</li>
<li>Despite handling lots of sine waves, the program only uses basic arithmetic operations. It does not depend on <code>libm</code>.</li>
<li>All type punning is done with <code>memcpy</code> so there are no strict-aliasing violations.</li>
<li>The size of the source code using the IOCCC size tool is 1963, the year the first push-button telephones were made available to customers.</li>
<li>The source code is roughly in the shape of a telephone handset.</li>
</ul>
<h3>Assumptions</h3>
<ul>
<li>Code is compiled using the C99 or C11 standard</li>
<li><code>CHAR_BIT == 8</code></li>
<li>Machine is little-endian</li>
<li><code>int16_t</code>, <code>uint16_t</code>, and <code>uint32_t</code> exist</li>
<li><code>int16_t</code> is 2&rsquo;s-complement</li>
<li><code>double</code> is an IEEE 754 binary64 floating-point type</li>
<li><code>sizeof(double) == 8</code></li>
</ul>
<h3>Obfuscations</h3>
<ul>
<li>DSP code is inherently somewhat difficult to understand.</li>
<li>Lots of identifier reuse. Each identifier is used for about 2.2 different tasks, on average.
For example, <code>aa</code> is both a variable and a macro for error handling,
and <code>memcpy</code> is both a library function and a goto-label.</li>
<li>Most of the identifiers are only 1 or 2 characters long, and are unrelated to their actual function.</li>
<li>The <code>f</code> macro is used to unroll some of the loops.</li>
<li>Some numerical constants are replaced with character literals, so the actual value is unclear.</li>
<li>All of the strings used by the program have been combined into a single string literal.</li>
<li>Most of the values used for the actual signal-processing all reside in one array, named <code>l</code>. This array is usually accessed at index <code>z</code> plus a constant. Accesses of this type have been rewritten from, e.g. <code>l[z+17]</code> to <code>17[l+z]</code>. <code>[l+z]</code> ends up occurring quite often, so I created the macro <code>a</code> as a shorthand.</li>
</ul>
<h3>Algorithm Details</h3>
<p>Each tone in a DTMF signal is a combination of two frequencies. The lower frequency determines which row the digit is in, and the higher frequency determines the column. There are 4 possible row frequencies and 4 possible column frequencies.</p>
<table>
<thead>
<tr>
<th> </th>
<th> <strong>1209 Hz</strong> </th>
<th> <strong>1336 Hz</strong> </th>
<th> <strong>1477 Hz</strong> </th>
<th> <strong>1633 Hz</strong> </th>
</tr>
</thead>
<tbody>
<tr>
<td> <strong>697 Hz</strong> </td>
<td> 1 </td>
<td> 2 abc </td>
<td> 3 def </td>
<td> A </td>
</tr>
<tr>
<td> <strong>770 Hz</strong> </td>
<td> 4 ghi </td>
<td> 5 jkl </td>
<td> 6 mno </td>
<td> B </td>
</tr>
<tr>
<td> <strong>852 Hz</strong> </td>
<td> 7 pqrs </td>
<td> 8 tuv </td>
<td> 9 wxyz </td>
<td> C </td>
</tr>
<tr>
<td> <strong>941 Hz</strong> </td>
<td> * </td>
<td> 0 </td>
<td> # </td>
<td> D </td>
</tr>
</tbody>
</table>
<p>This program determines which frequencies are present in the input by passing it through a set of 8 virtual resonators, each tuned to one of the frequencies used for DTMF. These can be implemented using only basic arithmetic, and they are able to &lsquo;select&rsquo; a specific frequency from the input sound, blocking all other frequencies from reaching the output. The loudness of the sound output from each resonator can therefore be used as a measure of how much of a particular frequency was present in the input. The program then decides, over the course of one tone, which row frequency and which column frequency were most prominent.</p>
<p>Tones are generated using those same resonators by providing <a href="https://en.wikipedia.org/wiki/Kronecker_delta#Digital_signal_processing">an impulse</a> as input. An impulse can be thought of as consisting of sine-waves at all frequencies, and when it is put through one of the resonators, the result is a single pure sine wave.</p>
<BR>
<HR>
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<TD><a rel="license" href="https://creativecommons.org/licenses/by-sa/3.0/"><img alt="Creative Commons License" style="border-width:0" src="/png/by-sa-3.0-88x31.png" /></a></TD>
<TD><P>&copy; Copyright 1984-2020,
<A HREF="/judges.html">Leo Broukhis, Simon Cooper, Landon Curt Noll</A>
- All rights reserved<BR>
This work is licensed under a <a rel="license" href="https://creativecommons.org/licenses/by-sa/3.0/">Creative Commons Attribution-ShareAlike 3.0 Unported License</a>.</P></TD>
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2020/giles/pi.wav
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2020/giles/prog.c
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#ifdef _WIN32
#define _CRT_SECURE_NO_WARNINGS
#include <io.h>
#include <fcntl.h>
#define X ;_setmode(_fileno(h),_O_BINARY)
#else
#define X
#endif
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#define a [l+z]
#define m(aa) z=aa;z=z;;
#define g(g,a)memset(g,0,a);
#define e2(a,g)!fread(a,g,1,h)
#define aa(a)fprintf(stderr,"%s\n",a);return 1;
#define n(n) b=n-i;b=b<0?1+b:1-b;d[n+2]+=b>0?b*c*aa:0;
#define t(t) z=t;b=(1-6[d])*d[2]+2*17 a*0 a-1 a*d[6];1 a=0 a;0 a=b*6[d];
#define f(f,aa) x=0; f(2)aa f(10)aa f(6)aa f(12)aa f(4)aa f(8)aa f(14)aa f(0)aa
#define j if(w){b=-1;char j=0;f(m,if(32 a>b){b=32 a;j=k[z];}if(33 a>b){b=33 a;j=k[z+1];})putchar(j);}
const char*t=
"Dual-tone multi-frequency signaling"
"(DTMF) is a telecommunication signaling"
"system using the voice-frequency band"
"Invalid WAV input\0Read "
"error\0Cannot read dtmf.bin\0rb\0"+111;
int main(int m,char**f){double aa,c,d[8]={[
6]=--m?1:0.994,[7]=1e-4},g,i=0,l['0']={0},b,
e2=0,x;char k[':'+'s'];FILE*h;if(!(h=fopen(t+
')',t+'2'))){memcpy: aa(t+'A'-'$')}uint32_t p=
e2(k+'U',',')||e2(l+16,'C'+'=')||e2(k,'Q'),w=0
,o[2],z,n;fclose(h);if(p)goto memcpy;setvbuf(h
=m?stdout:stdin,0,_IOFBF,65536)X;uint16_t e,v;
int16_t r;if(m){m(6400*strlen(*++f))mem\
cpy(k+'+'+'R',&z,4);z+='$';me\
mcpy(k+'Y',&z,4);fwrite(k+'U',
',',1,h);while(**f){char*c=st\
rchr(k,*(*f)++);g(l,'F'+':')if
(c){w=c-k;double*n=l+w%4*2;*n
=n[16];n=l+8+(w/4)%4*2;*n=n[
16];}for(w=3200;w;--w){f(t,x
+=b*e2*49e2;)r=x;fwrite(&r,2
,1,h);e2+=(w>1300?1:-1)*3e-2
;e2=(e2>1?1:(e2>0?e2:0));}}}
else{ if(e2(k+'+'+'V',',')){
fread:aa(t+18)}if( memcmp(k+
'+'+'^',k+']',14)){ int_16t:
aa(t)}memcpy(&n,k+'+'+'n',4)
;c=16e3/n;n=c; if(n!=c)++n;c
/=n;memcpy( &v,k+43+'x',2);v
/=8; memcpy(&e,k+'+'+'v',2);
if(!e||!v||v>4)goto int_16t;
e-=v;while(!e2(k+'Q',v)){m(e
)while(z-- && getc(h)>=0);if
(v>1){memcpy(&r,k+v+'O',2);g=r/512\
.0/'@';} else g=(unsigned char)k['Q']/128.0-1;
for(p=n;p;--p){aa=(e2-g)*p/n+g;n(0)n(1)n(2)i+=
c;if(i>=1){g(d,16)g(o,8) f(t,b=0 a-d[6]*17 a*1
a;aa=d[6]*1 a*16 a;aa=b*b+aa*aa;x+=aa;if(aa>=d
[z/8]){o[z/8]=z/2;d[z/8]=aa;})if( (r=w?x>d[7]*
0.45:x>d[7]*0.6)){if(!w)g(l+32,128)if(x>d[7])
d[7]=x; /* x= (-b+sqrt(b*b-4*a*c))/(2*a); */
++ l[16+o[1]*4+*o];}else j w=r;memmove(d+2,d+3
,24);--i;}}e2=g;}if(ferror(h))goto fread
;j puts("0123456789"+10);}return 0;}