Broadcasting images
This page documents how to broadcast images over sound on FM radio using BotWave.
To achieve this, BotWave supports SSTV generation and broadcast.
SSTV, or slow-scan television, is a way of transmitting images using sound signals. It was first introduced by Copthorne Macdonald in 1957-58.
SSTV dependencies are not installed by default. This means you'll have to install them manually before starting an SSTV broadcast.
Warning
This may take some time and will triple the base-install disk size.
sudo /opt/BotWave/venv/bin/pip install pysstv numpy pillowThis example shows how to start an SSTV broadcast on the local component. The process is the same for the server one.
Start by launching a BotWave instance and, optionally, downloading an image:
sudo bw-local
[...]
botwave> < curl -O https://images.dpip.lol/bw-logo.pngThen simply start a broadcast using the SSTV command:
botwave> # command syntax: sstv <image_path> [mode] [frequency] [loop] [ps] [rt] [pi]
botwave> sstv bw-logo.pngExample output
botwave › sstv bw-logo.png[SSTV] Generating SSTV WAV from bw-logo.png using mode auto... [SSTV] SSTV wav created /tmp/bw_sstv/e17b2314c436391d.wav (mode: PD160) [OK] Started broadcasting /tmp/bw_sstv/e17b2314c436391d.wav on 90MHz
You can choose an encoding mode using the mode positional argument. All available modes can be found here.
If the mode is left empty, BotWave will automatically choose the best mode based on the image you provided.
botwave> # using the "Robot36" mode on 99Mhz
botwave> sstv bw-logo.png Robot36 99Example output
botwave › sstv bw-logo.png Robot36 99[SSTV] Generating SSTV WAV from bw-logo.png using mode Robot36... [SSTV] SSTV wav created /tmp/bw_sstv/5ed86d7d2921e0d9.wav (mode: Robot36) [OK] Started broadcasting /tmp/bw_sstv/5ed86d7d2921e0d9.wav on 99.0MHz
To decode the image, you can use a tool like Robot36, available on the Google Play Store. Simply tune a radio to the broadcast frequency and start the app to decode the image.
