radio

[Lowtone]

Hello

i wanted to experiment with PMR like radios.
Is there an encoding/decoding software that can convert files to formats that fit in a such narrow narrow bandwith ?

[Klaas Robers]

What is it that you want to do? File transfer? Do you want to send and receive computer files via the small 460 MHz PMR walkie talkies? Then you could go in and out via the sound blaster of your PC. The sound bandwidth is about 2.5 kHz. Should be possible, but I don't know if there is any standard software for.

[Lowtone]

I would convert a video file to NBTV like format, that suits radio limitations, and send the signal by radio, to test the quality of this.
I tested some SSTV yesterday, and it brought me back to NBTV

I remembered this https://www.youtube.com/watch?v=7klqrR3TAoQ
but how is it done ?
standard NTBVA format seems not narrow enought for radio

[gary]

I would convert a video file to NBTV like format, that suits radio limitations, and send the signal by radio, to test the quality of this.
I tested some SSTV yesterday, and it brought me back to NBTV

I remembered this https://www.youtube.com/watch?v=7klqrR3TAoQ
but how is it done ?
standard NTBVA format seems not narrow enought for radio

In Video2NBTV you will see a format called "Chris Long Shortwave" - that Chris and I designed to overcome (some of) the limitations shown in the video (that's Chris BTW). That would have been just the NBTVA standard low pass filtered to suit the available transmission bandwidth and so just cut off the higher frequencies - the Shortwave version is just an optimised version of doing that as, well, that is all you can do.

There is also the Vic Brown shortwave format using Vestigial Sideband Modulation - but that is a bit more complex requiring hardware to decode.

[DrZarkov]

There is a format called "digital NBTV", which could be what you are looking for: http://www.qsl.net/zl1bpu/NBTV/Digital.htm

[Lowtone]

thanks i will try that
edit : ah no, the framerate is too slow, it's SSTV

gary > thanks, but with wich software will i be able to play/recieve those files ?

[gary]

gary > thanks, but with wich software will i be able to play/recieve those files ?

The usual: Video2NBTV to create the video and TBP-V2a to play back (or preferably a mechanical monitor for the latter ).

[Lowtone]

I only get a black screen

[gary]

I only get a black screen

Explain to me the procedure you are using.

(also the version of TBP you are using).

[Lowtone]

Hello,
i made an .avi file with a video editor. Then i conveted it to .wav file with Video2NBTV-n3 alpha
this went nice.
Now i try to open the .wav file with The Big Picture V2 alpha ( i'll try on the televisor when i'll find where the heck it could be stored )
So what happen : i tried different modes
Vic Brown : format type 10 not correctly supported
NBTVA Color : format type 8 not correctly supported
Chris Long optimised : format type 0 not correctly supported
Chris Long : no error message, i hit "capture" nothing seems to happen
I play with the level button, there are some pixels here and there
Frame, line and sync seems to have some effects, but the picture is not steady at all, and also too dark

[gary]

Ok, let's get a couple of things straight, Firstly we are only talking about the "Chris Long Shortwave" format. Forget, for the moment, the other formats. There is never a guarantee that the 2 applications are format compatible - I get a lot of requests for "special" formats in Video2NBTV that I try to respond to, but there is no reason to add that format to TBP.

However, when I am involved with the format there is generally support included in TBP (sometimes another application).

In this case I was involved with the format and so it is definitely supported in TBP.

Here is an example of the format I have just created:

erection.wav

(7.12 MiB) Downloaded 598 times

and this is what it looks like when played via TBP:

output.avi

(15.77 MiB) Downloaded 569 times

Let me know if you can play the example.

Edit:

Oh I think I know what the problem is - to reduce the bandwidth required this format DOES NOT HAVE SYNC - so turn it off and it should correct the problem.

[Lowtone]

http://www.mediafire.com/view/2zs6hjxztp7sqz5/testnbtv.PNG
Here's what i get. ( it moves )
I don't know what i did wrong, i haven't use those softwares since a few years

[gary]

Did you turn sync processing off?

[Lowtone]

no ah it works now !!! thanks you

[gary]

You are welcome, in truth, as the format doesn't use sync TBP should ignore the "process sync" flag I suppose - aah well no one is perfect.

Of course, in practice, when receiving a signal via a shortwave receiver, you would need to use the Line and Frame adjustments to lock the picture - that is, of course, why they are there.