Troubleshooting

Garbled deconvolve

If deconvolve or vbiview gives you only garbled output, with sometimes one or two lines readable, it could be that it was compiled with a too old version of numpy installed. In a test-case numpy 1.17.4 was not compatible with the teletext tool. It might be, that numpy has to be at least 1.18. It was successfully tested with numpy 1.21.5. So if you experience that behavior, uninstall numpy and install a newer version of it. It can be, that you also have to reinstall miniaudio, spectrum, watchdog. Just install them again and recompile vhs-teletext.

Detuned capturecard

It happens, that the capture-card starts to forget brightness and contrast settings and starts to drift towards ultra bright. This can be avoided by starting and stopping playback approx. every 10 minutes in the v4l2 tools while recording teletext. To test that behavior let vbiview run for 20 to 30 minutes and check if the vbi lines get more and more bright and become unreadable. If so, hit the play button in v4l2 while vbiview is open. It should jump back to the correct brightness levels and teletext is recognized again.

This might be an automatic way to reset the card values while capturing.
while true ; do ffmpeg -y -f video4linux2 -i /dev/video0 -t 0:10 -f null - ; sleep 10m ; done loop