Mike:

Yes, that quite well proves you don't even have a clue where to begin
and what would be a practical method to accomplish it...

.... don't feel alone, these ancient brain deads here are in the same
boat and have ran off and ****ed off all those who can do such
things...

.... at first I just thought you guys were probably not interested in
video conferance by radio--now I find out you are simply unable and
even lack the basic concept of how it is done!

John

"Mike Coslo" wrote in message
...
Dee Flint wrote:
"Michael Coslo" wrote in message
...

Dee Flint wrote:


"John Smith" wrote in message
...


Dee wrote, "... only fax and SSTV have a small enough band width
to be practical."

That is not only a ridiculous statement, it is preposterous and
shows a total lack of knowledge of the state of data compaction.

However, it proves you are not aware of what is technically
possible and therefore are in a poor position to advise or inform
others and, the sorry state of amateurs technical savvy in
general!

John



Ok then, show me the math that demonstrates you can transmit a one
megabyte picture in seconds on the HF bands using only 300 baud.
To get it down to seconds requires data compression/encryption
techniques that can reduce the data by a 1000 fold.

Obviously, images can be transmitted by digital modes as well as
the analog method of SSTV.



Digital images would have to be compressed/encrypted also to get
the bandwidth down to acceptable ranges for HF and we're still
talking on the same order of magnitude to do so. Even with a fast
broadband internet connection, I've seen some material that still
takes a noticeable time to download.


Is that a good way of transmitting the image? It can be. Seems I've
heard about a digital image transmission mode.



Isn't most of the stuff off the internet (mpg comes to mind)
digitally encoded. Even on my broadband connection it will
occasionally jerk and pause. If you have to slow it down to 300
baud for the HF bands so as not to consume too much bandwidth, that
would become even jerkier.

Very true.

Accepted minimum rate for a recognizable "talking head" type video
is 32Kbit/second.

I made a test jpg image @ 640 by 480, level 5 (unacceptable for me,
but others may find that okay) Typical scene, some amateurs sitting
around a radio, no large expanses of sky. It was 553.6 Kbits.

Assuming that the transmission rate would be similar to Packet radio
at .3Kbit/second it is obvious that video would be impossible to do
live, and grossly impractical to do as say an mpeg.

That 640 by 480 jpeg might be within the realm of feasibility at
just around 31 minutes. Note that this does not include error
checking lags. And there will be errors.

Note that these are very rough calculations.


Does that make the Analog SSTV mode obsolete? No more obsolete than
SSB or FM. It is a fairly quick mode, and with a computer is now
inexpensive, and fun.

I'm looking forward to an education on the modes from someone with
technical savvy. Mr Smith?


- Mike KB3EIA -


I doubt if he's got the technical savvy. Simple arithmetic shows
the inherent problems.

Yeah, like I said 8^)

- Mike KB3EIA -