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authorMattias Andrée <maandree@member.fsf.org>2015-12-19 21:35:54 +0100
committerMattias Andrée <maandree@member.fsf.org>2015-12-19 21:55:35 +0100
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a nice readme
Signed-off-by: Mattias Andrée <maandree@member.fsf.org>
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-File over dual-tone multi-frequency signaling
+NAME
+ fodtmf - Transfer files over audio.
+
+ETYMOLOGY
+ File over DTMF (dual-tone multi-frequency signaling)
+ ~ ~ ~~~~ ~ ~ ~ ~
+
+SYNOPSIS
+ fodtmf-send [OPTIONS] [< FILE]
+
+DESCRIPTION
+ fodtmf-send shall send the file FILE over audio
+ encoded with dual-tone multi-frequency signaling.
+
+ The message will be enhanced with hamming code
+ for error correction, and optionally with
+ redundant frequencies to help combat noice in
+ the environment.
+
+ At the end of the transfer, an 'end of transmission'
+ byte will be send. If the message is cancelled, a
+ 'cancel' byte will be send. The end of the message
+ will be padded with this byte until a full error
+ correcting code has been constructed.
+
+ For any 'data link escape' byte, any 'end of
+ transmission' byte, and any 'cancel' byte in the
+ transmitted file, a 'data link escape' byte will
+ be inserted directly before it.
+
+OPTIONS
+ -f MULTIPLE
+ In addition to any tone with the frequency
+ F, also send, simultaneously a tone with the
+ frquencies F times MULTIPLE. This is a
+ rundundant to to improve the reliability of
+ the transfer. Rundundant tones are not added
+ by default because they make the tones less
+ pleasant.
+
+ -r N
+ In each error correcting code, include N
+ parity bytes. By default, this is three. The
+ higher this value is, the less redundancy the
+ code will have. The number of bytes per code is
+ calculated by 2^N - 1, and the number of data
+ bytes per code is calculated by 2^N - N - 1.
+
+ There are two exceptional values, that cases
+ the message to be transferred without any
+ hamming code for error correction:
+
+ 0 Do not include any redundancy at all,
+ apart from any specified using the
+ flag -p.
+
+ 1 Only one redundancy byte per code,
+ apart from any specified using the
+ flag -p.
+
+ This value must be non-negative.
+
+ If this value, plus 1 if -p is used, equals
+ 1, the receiver may be able to spot errors,
+ but has no chance of repairing them, unless
+ additional error correction mechanisms are
+ added. If it equals 0, the receiver will
+ be unable to spot errors unless additional
+ error correction mechanisms are added.
+
+ -p
+ Include one extra parity byte per error
+ correcting code. This byte will be the
+ parity of all data bytes.
+
+ -o FD
+ Write the audio to file descriptor FD rather
+ than playing it back. This is intended for
+ development purposes only. The written file
+ will not contain any metadata to hint how
+ it is encoded and how it should be played
+ back.
+
+ Each option can only be used once.
+
+RATIONALE
+ I really don't know precisely why. But it sounded fun.
+
+SEE ALSO
+ scp(1), nc(1)