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@@ -1,2 +1,91 @@ -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) |