HD NBTV?

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HD NBTV?

Postby Steve Anderson » Tue Feb 12, 2008 1:43 pm

...from another thread...

Panrock wrote:....Volker could bring his two 80-line discs over with him when he visits Britain, that is - if he finds it convenient. Steve


Hmm..interesting. I thought that Steve O (Panrock) was out there on his own going to 80 lines, but it appears that Volker is too. Is this slowly developing into a 'high-definition' version of NBTV I wonder?

If so, I'm all in favor of it and especially Steve's adoption of the 4:3 'widescreen' aspect ratio.

For some months now I have been considering going to 48 lines....no big deal one thinks...but with a 4:3 aspect ratio. *People start fidgeting.* ...and here's the crunch.... using left-to-right/top-to-bottom scanning as in conventional TV, similar to the German mechanical system. *An uproar starts.*

In monochrome this fits very neatly into the bandwidth of an audio CD or a .wav file sampled at 48kHz. However in view of the work done by the gents mentioned I'm getting very tempted to follow in their footsteps.

I know there will be those that say it's nothing like what Baird did, well not quite, I think he went on to far higher resolutions, I believe up to 240 lines. These were never transmitted (at least to the general public), but it shows he realised the shortcomings of 30-line TV.

This would be an adjuct to the existing 32-line system, not to surplant it.

Many years ago I remember reading about MDTV, (Medium Definition TV), not sure what happened to it.

Feedback gents.......

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Postby DrZarkov » Tue Feb 12, 2008 6:08 pm

No, I'm (currently) not going onto 80 lines, I'm more interested in 60 lines. A friend of mine is making the discs. Of course he must do it, when normal business is a little bit calmer, so the discs are not ready yet. I've called him last thursday for the last time. By making only 4 discs the price will be around costs of material or less.
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Postby Panrock » Tue Feb 12, 2008 8:29 pm

I seem to recall that many years ago Alan Short successfully demonstrated a 90-line Nipkow display; he was a brave pioneer - this was before the possibility of CNC or laser. The most noticeable defect was that small errors in the (very critical) positions of the holes led to a smeary looking picture.

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Re: HD NBTV?

Postby gary » Tue Feb 12, 2008 10:00 pm

Steve Anderson wrote:...from another thread...

Panrock wrote:....Volker could bring his two 80-line discs over with him when he visits Britain, that is - if he finds it convenient. Steve


Hmm..interesting. I thought that Steve O (Panrock) was out there on his own going to 80 lines, but it appears that Volker is too. Is this slowly developing into a 'high-definition' version of NBTV I wonder?

If so, I'm all in favor of it and especially Steve's adoption of the 4:3 'widescreen' aspect ratio.

For some months now I have been considering going to 48 lines....no big deal one thinks...but with a 4:3 aspect ratio. *People start fidgeting.* ...and here's the crunch.... using left-to-right/top-to-bottom scanning as in conventional TV, similar to the German mechanical system. *An uproar starts.*

In monochrome this fits very neatly into the bandwidth of an audio CD or a .wav file sampled at 48kHz. However in view of the work done by the gents mentioned I'm getting very tempted to follow in their footsteps.

I know there will be those that say it's nothing like what Baird did, well not quite, I think he went on to far higher resolutions, I believe up to 240 lines. These were never transmitted (at least to the general public), but it shows he realised the shortcomings of 30-line TV.

This would be an adjuct to the existing 32-line system, not to surplant it.

Many years ago I remember reading about MDTV, (Medium Definition TV), not sure what happened to it.

Feedback gents.......

Steve A.


Steve, are you aware that Vic Brown has developed a 60 line colour (black and white compatible) monitor along the lines of his 32 line colour system but left to right top to bottom and that the current version of Video2NBTV produces this format? (96kHz). Vic's system requires that the data be delivered digitally for colour but a monochrome system can be analogue. (I hope I haven't let a cat out of the bag there).

Certainly anyone wanting to experiment with 60 line horizontal scanning can use Video2NBTV as a source of video.
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Postby Steve Anderson » Wed Feb 13, 2008 12:56 pm

Thanks for the feedback gents....

48, 60, 80, 90 lines? It's a pity that some form of standard hasn't been agreed, but there's probably good reason for each person choosing the number of lines they have.

A logical (pun intended) development to me would have been 64 lines, simply double the current usual 32. The direction(s) of scanning and aspect ratio? ...to be discussed.

I initially chose 48 as it's 1.5 times 32 and the bandwidth requirements just fits on an audio CD. Any more than this and audio CDs are unsuitable.

Now I'm in a quandary, I'll have to dwell on this for some time.

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Postby DrZarkov » Wed Feb 13, 2008 6:47 pm

The problem with "HD NBTV" is how to get a signal to the monitor wothout maiking a camera first. 48 lines should be no problem for a PC, 60 lines will work maybe, maybe not if you choose 25 frames/sec. For 180 lines and more (the king-class of mechanical TV I think) some graphic boards can be used with this software: http://www.g1jbg.co.uk/fothtv.htm.

Maybe we need a digital output via USB and a converter which gives us three colour channels.
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Postby Steve Anderson » Thu Feb 14, 2008 1:30 pm

DrZarkov wrote:The problem with "HD NBTV" is how to get a signal to the monitor wothout maiking a camera first.


Agreed, it's a 'chicken and egg' situation, which one comes first? My approach would be to build the monitor first, but prior to that an electronic source to get it going. Assuming that PC sound cards are not up to the job, a generator based on the EPROM designs of the past brought up-to-date by using EEPROMs.

First one needs to define the standards to be used, no. of lines, scanning directions, aspect ratio and frame rate as a start. Colour or monochrome? This is my quandary.

For the current 32-line system it's well defined by the club and has been for many years which has allowed things like the CDs and various software to be produced. However, as yet there's no standard adopted for 'HD NBTV'.

As this is a minority interest perhaps 'standards' are not needed and each person remains an isolated island, or just a few agree to 'do it this way'.

...I'm still ruminating over this....

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Postby DrZarkov » Thu Feb 14, 2008 5:41 pm

I suggest a "classic standard" like 48 or 60 lines, 25 frames progressive scanning, horizontal scanning starting at the top left, aspect ration 3:4 like it was in use in Europe an USA in that time. There are some 60 lines televisors, made by Peter Yanczer and others. I don't know which frame rate they are using. They use an Aurora converter, but there must be a cheaper way to convert the picture.
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HD-NBTV.

Postby Stephen » Fri Feb 15, 2008 12:52 am

I agree that there should be some degree of standardisation in approaching higher definition television that exceeds the ordinary audio channel bandwidth. I believe that the American television channels, between 2.0 and 3.0 mHz, had a bandwidth of 100 kHz, which permitted a 50 kHz video signal with double sideband AM. We might consider 50 kHz as a reasonable limit for such standardisation.

I also agree with Volker that a 3:4 aspect ratio with horizontal left-to-right scanning would be most appropriate. With respect to line count, the number of scanning lines should be divisible by three as well as by two to allow for future experimentation with line sequential colour systems. This would dictate line counts of perhaps 42, 48, 54 or 60 lines.

I would suggest a frame rate of 48 to 50 fps for grey scale systems. This would allow compatibility with experimental field sequential colour systems which would then have a colour frame rate of 1/3rd this value, or 16 to 16-2/3 fps.

Let us consider a 48 line system at 50 fps. "Theoretical" bandwidth would be 48×64×25=76.8 kHz. However, as I have indicated in other threads, considering a normal Kell factor of 0.7, the actual bandwidth for equal effective horizontal and vertical resolution with this line count would be 76.8×0.7=53.7 kHz, which bandwidth would approximate a 50 kHz channel. The effective resolution with the Kell factor considered would be 33 by 45 pixels.

Let us consider a 42 line system at 50 fps. Let us also assume that it employs overlapping scanning frames as I have described in other threads and includes frame sequential colour. The colour frame rate would be the individual 50 fps colour field frame rate divided by 3, or 16-2/3 fps. The theoretical bandwidth would be 42×56×25=58.8 kHz. The overlapping frames would increase the Kell factor considerably, possibly to 0.9. The resulting bandwidth would then be 58.8×0.9=52.9 kHz, again approximating a 50 kHz channel. The effective resolution would then be 38 by 50 pixels, higher than the 48 line system described above!
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HD-NBTV.

Postby Stephen » Fri Feb 15, 2008 5:07 am

An ordinary 60 line system with a 4:3 aspect ratio at 12.5 fps could just fit within an ordinary audio channel. Although the theoretical bandwidth would be 60×80×62.5=30 kHz, with a Kell factor of 0.7 and equal effective horizontal and vertical resolution the bandwidth would fall to 30×0.7=21 kHz. The effective resolution would be 42 by 56 pixels.
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Early HD-NBTV.

Postby Stephen » Fri Feb 15, 2008 7:03 am

Looking around for more information about the early American television stations that used systems with a relatively high line count, I came across the web pages http://www.earlytelevision.org/don_lee_ ... tions.html , relating to broadcasts by the Don Lee Broadcasting System in Los Angeles, California, using an 80 line, 15 fps system. These pages include a letter, dated 11 December 1933, to a listener in Missouri that picked up the television station signal. The letter indicates that the station was broadcasting feature films and news reels daily and includes complete instructions for constructing an 80 line, 15 fps television receiver!
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Postby jim_beacon » Fri Feb 15, 2008 9:26 am

DrZarkov wrote:The problem with "HD NBTV" is how to get a signal to the monitor wothout maiking a camera first. 48 lines should be no problem for a PC, 60 lines will work maybe, maybe not if you choose 25 frames/sec. For 180 lines and more (the king-class of mechanical TV I think) some graphic boards can be used with this software: http://www.g1jbg.co.uk/fothtv.htm.

Maybe we need a digital output via USB and a converter which gives us three colour channels.


Thanks for the website plug :D

I'm not able to do anymore development on the FOTH tv project at the moment, as we have recently moved house, and I don't know if Kat Manton (the originator of the project) is activly devloping at the moment.

180 line is the lowest resolution that we have achieved so far, but it may be possible to go lower - there are a number of issues with lowering the line rate.

Vertical scan is more of a challenge, and it may be easier to provide a hardware converter to do that, but it is on my list of things to investigate!

I do know where (most) of the relevant hardware is after the move, but I don't have any workspace at present, and I also need to rebuild my home network, as the project development is aided by having a local FTP server, and my trusty VAXstation is currently languishing behind a pile of valve radios......

I'll keep you updated when there is more to report.

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Re: HD-NBTV.

Postby Steve Anderson » Fri Feb 15, 2008 2:09 pm

Stephen wrote:I agree that there should be some degree of standardisation in approaching higher definition television that exceeds the ordinary audio channel bandwidth......we might consider 50 kHz as a reasonable limit for such standardisation.

I also agree with Volker that a 3:4 aspect ratio....


Stephen, thanks very much for your input, and think that your comments are very much in line with my thoughts and the direction I might take.

Do you really mean 3:4? i.e. still a 'portrait' format? As I'm thinking of going to 4:3, as in conventional 525/625 TV, the same as Steve O has done with his colour camera and display.

Steve A.

P.S. Welcome on board Jim...excellent web-site too!
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Re: HD-NBTV.

Postby Stephen » Sat Feb 16, 2008 12:50 am

Steve Anderson wrote:Do you really mean 3:4? i.e. still a 'portrait' format? As I'm thinking of going to 4:3, as in conventional 525/625 TV, the same as Steve O has done with his colour camera and display.
Yes, I meant 4:3 and inadvertently wrote 3:4.
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HD-NBTV on short-wave.

Postby Stephen » Sat Feb 16, 2008 1:07 am

I am just amazed that Americans were able to able to receive "HD-NBTV" broadcasts on short-wave with 48-80 line, 15-20 fps pictures in the early 1930s over great distances! I think that 100 kHz channels on the 2-3 mHz band for such experimental televison transmissions are a great idea. Perhaps the NBTVA should petition the ITU for such a recommendation.... :lol:
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