Author:

• Name: Daniel Vik
  Location: US - United States of America (United States)

To build:

    make

There is an alternate version that will theoretically work with Windows compilers (if anything in Windows works :-) ). See the Alternate code section below.

Bugs and (Mis)features:

The current status of this entry is:

STATUS: known bug - please help us fix

For more detailed information see 2014/vik in bugs.html.

To use:

    echo foo | ./prog > audio_file.raw

    echo foo | ./prog | mplayer -demuxer rawaudio -

Try:

    ./try.sh

Alternate code:

The alternate code, prog.alt.c, is based on the author’s instructions on how to get it to work with Windows.

Alternate build:

    make alt

Alternate use:

Use prog.alt as you would prog above as well as below.

Judges’ remarks:

This program sets a new tone for obfuscation. But do you understand what it says about obfuscation? Perhaps:

    ./prog < prog.c > prog.raw

might speak to your coding style? If not, then perhaps:

    ./prog < README.md | mplayer -demuxer rawaudio -

might help? :-)

Author’s remarks:

Remarks

This program converts ASCII text to Morse audio file and vice versa. As far as I can tell, there are at least six chocolate references in this program.

This program can convert text to Morse to a raw 44.1kHz stereo audio file. Via streaming to mplayer(1), you can listen to the Morse audio.

Don’t forget the last ‘-’ as it makes mplayer(1) read from stdin.

Convert audio file with Morse signals to text

    ./prog e < audio_file.raw

or alternatively pass a .wav file as input.

The preferred input format 44.1kHz stereo, but it does a decent job on mono input and different frequencies as well.

Portability

The program is portable to most platforms. The only system dependency is that the program relies on writing binary data to stdout.

Microsoft compilers add a carriage return to newlines, and to compile the program with this platform, the following line can be added to main() before any code in order for the program to run correctly:

    _setmode(_fileno(stdout), 0x8000);

NOTE: see the alternate code for this.

Known Issues

The program uses a quite simple algorithm for detecting tone on and off events in the Morse signal. Hence the program does not work well with noisy input signals. I have tested it with several samples of man made Morse recordings as well as computer generated ones.

Generally, any recording from ham radio transmissions does not decode due to noise and echoes. Other man made recordings may decode, but some characters can be incorrect due to too big variation in length of tones and pauses. However I found some man made recordings on that decode reasonable well.

If a recording doesn’t decode, you could try to pre-process the input with a narrow bandpass filter on the frequency of the transmission.

Primary files

• prog.c - entry source code
• Makefile - entry Makefile
• prog.alt.c - alternate source code
• prog.orig.c - original source code
• try.sh - script to try entry

Secondary files

• 2014_vik.tar.bz2 - download entry tarball
• README.md - markdown source for this web page
• .entry.json - entry summary and manifest in JSON
• .gitignore - list of files that should not be committed under git
• .path - directory path from top level directory
• index.html - this web page

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