SSTV fast enough as a compromise to nbtv?

Forum for discussion of SSTV topics. Slow Scan television (SSTV) is a picture transmission method used mainly by amateur radio operators, to transmit and receive static pictures via radio in monochrome or colour.

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SSTV fast enough as a compromise to nbtv?

Postby sv3ora » Mon Nov 25, 2019 7:47 am

Hi,
What if there was an SSTV mode that would allow for a very small resolution video to be split into images and send them in a sequence using a fast SSTV mode? (robot 8?)
Would the "refresh rate" of the images be high enough to give the impression of a video at the receiver?
Is there such a mode/program written?
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Re: SSTV fast enough as a compromise to nbtv?

Postby Steve Anderson » Mon Nov 25, 2019 3:47 pm

The brick wall you hit is always bandwidth - the amount of information sent down a communication channel.

SSTV was originally 120x120 pixels per frame, monochrome, at about 7-8 seconds per frame. This requires a bandwidth of about 1kHz - easily fits down a phone line or via HF Amateur Radio.

NBTV may only be 32x48 pixels per frame (using a common-ish arrangement) but the frame rate is 12.5 frames per second. This will not fit down a telephone line or via HF radio as the bandwidth required is in the order of 10kHz, ten times greater - and no sound. (Neither does SSTV, but SSTV is really a sequence of stills).

It doesn't make any difference how you 'chop up' the signal it still needs to get from one end to the other intact. You can't send every other character in a book and hope it'll be understandable. Sure, you can compress signals, Winzip, jpeg etc. but there's always a trade-off somewhere.

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Re: SSTV fast enough as a compromise to nbtv?

Postby Harry Dalek » Mon Nov 25, 2019 5:16 pm

Reminds me of something i posted chris long was playing with a few years back ,but can't remember where i put it more than likely in off topic i will have a look but you can make a wide range of frame and line rates with FreeNBTV posted on this forum .
viewtopic.php?f=23&t=2637&hilit=chris+long
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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