At 100 baud, 17 KB of data is equivalent to roughly half an hour (one side of a 60-minute cassette tape).
For this workshop we'll only be working with plaintext data.
❏ Open Sublime Text or a similar plaintext editor. Write a few lines of text, or paste in some text from the web.
❏ Save your file to the desktop with a name like text_file.txt.
❏ Open a new terminal window. In Ubuntu you can press ctrl + alt + t.
❏ Enter the following command to change your working diretory to the desktop:
cd ~/Desktop
❏ Run the following command, substituting the name of your text file if it's different. The "|" character is called a pipe; you can find it above the backslash on your keyboard.
cat text_file.txt | minimodem --write 100 -f modem_audio.wav
In the file explorer, find the WAV file you just created. To play it back, right-click the file and open it with VLC.
❏ Run the following command to convert your file to audio at 5 baud. That's slow! Make sure your input file is small, or this will create a huge audio file.
cat input_file.txt | minimodem --write 5 -f modem_audio.wav
In the file explorer, find the WAV file you just created. To play it back, right-click the file and open it with VLC.
Run the following command to see a list of options for minimodem:
minimodem --help
❏ Plug an audio cable into your computer's headphone output and connect the other side to the "line in" port on your tape recorder.
❏ Make sure your tape recorder is set to "tape" mode. Insert a tape and rewind to the beginning.
❏ Press record on your tape recorder.
❏ In the file explorer, find the audio file you want to record. To play it, right-click the file and open it with VLC.
❏ Plug an audio cable into your tape player's headphone output and connect the other side to the microphone input on your computer.
❏ In a terminal window, run the following command to receive data at 100 baud. The -q option means "quiet," which tells minimodem not to output unncessary text.
minimodem --rx 100 -q
❏ Press play on your tape player. After a few seconds you should see text start appearing in the terminal window.
If you don't see anything onscreen or the output is jumbled, try adjusting the tape player's volume up and down until it looks right.
❏ To stop displaying text onscreen, press ctrl + c.
❏ To clear the terminal window, run the clear command.
clear
If you want to convert an audio file containing modem audio directly to a text file, you can use a command like the one below. The file modem_audio.wav is a WAV audio file containing text data encoded at 100 baud. This command will write the text to a new file called output_file.txt.
minimodem --rx 100 -q --file modem_audio.wav > output_file.txt
❏ To store an image on a cassette tape, you may want to convert it to the text-based base64 format beforehand. You'll want to use a small image file, and store the data several times in case it gets corrupted.
base64 photo.jpg > photo_base64.txt
❏ You can use the du command to check how much disk space is being used by a file.
du -h photo_base64.txt
Convert an image to ASCII art from the command line:
ascii-image-converter -d 80,50 photo.jpg > photo.txt
Use an alternate color setting:
ascii-image-converter -d 80,50 -c photo.jpg > photo.txt
ascii-image-converter -d 80,50 -C photo.jpg > photo.txt
Alternate color setting:
ascii-image-converter -d 80,50 -c -C photo.jpg > photo.txt
Download video:
yt-dlp "http://video_url.com/1339482883"
Extract 1 frame per second to jpeg files:
ffmpeg -i "video_file.webm" -vf fps=1/1 img%03d.jpg
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