Narrow-Bandwidth Television Association

What you say Klaas is interesting, but I'm still in the dark as to the mechanism by which the missing sync pulse on the Nipkow disk and the missing sync pulse in the "video" signal are processed by the 4046 to create a frame sync.

For curiosity I made a simple signal generator using a PIC and a DAC to meet the NBTV standard as I understand it. It was a simple matter to produce PIC programs to generate signals with and without the missing sync. I found that the missing sync. made no difference to the displayed image, which was from a simple staircase signal with the 2.5ms negative going line sync. pulse.

On a different note, I have not been able to find any info on how to convert, say an .avi or .wmv file to the NBTV standard. I can imagine this is not a trivial task, but I'd like to have a go! Any offers?

mikew8760 wrote:On a different note, I have not been able to find any info on how to convert, say an .avi or .wmv file to the NBTV standard. I can imagine this is not a trivial task, but I'd like to have a go! Any offers?

There is actually quite a bit of software available in various states of usability. We have a forum section dedicated to it
viewforum.php?f=41

I think that I made in the past a Pascal program that converted a .bmp or a .gif still picture in an NBTV .wav file. I think it is one frame, so 1/12.5 second. This is easy expandable by copy / paste.

The CD's of the NBTVA were converted in hardware from 625 line standard scan video signal (from a Cam-Corder) into an NBTV video signal. That could be recorded on a CD-recordable disc, which creates a .wav file. This was how the video recordings from the NBTVA-meetings were recorded. I made programs to edit these .wav files, did time base correction and amplitude corrections, to produce .wav files that could be recorded again on to CD-R.

I never investigated how computer life-video files could be converted into NBTV .wav files.