German 180-Line System.

[Steve Anderson]

I've started this thread as the German 180-line system really doesn't come under the heading of '205-Lines?'.

With the data that Volker (Dr.Zarkov) has provided I've done some fiddling around with the calculator. For the time being I've crunched the numbers on the assumption I'll be using some form of digital signal generation/storage hence the use of pixels in the calculations. I've also ignored things like Kell factor for the moment.

25fps at 180 lines = 4.5kHz line rate (222.2us/line).
With an aspect ratio of 5:4 requires 225 active pixels/line.
256 is a nice binary number so 256 - 225 = 31 pixels for blanking, syncs and retrace (26.9us).
One pixel = 868ns, a pixel rate of 1.152MHz.
Bandwidth required (ideal) 550kHz.
It would appear that the system never used interlacing (pity), but I might.

1.152MHz is an awkward frequency, but multiplying this by 16 comes out to 18.432MHz...and would you believe it? My supplier has crystals in stock for that frequency!

Now I wouldn't hope for quick results on this, with the queue of things in the pipeline it could well be next year before I make a real start on this. But I am looking forward to it!

Steve A.

[Klaas Robers]

Steve, it is doubtable that the 180 line system had sync and blanking outside the 4:5 aspect ratio. In the mechanical systems the sync was inside the aspect ratio, so the 3:7 aspect ratio of the Baird televisor was only available if there was no sync at all. So is there any data available about that?

However for "the brute" it isn't a problem at all, you may simply adjust the picture width to make a circle round.

If you like to make a video generator, you might use the PCB of the EPROM generator and do some patches to the divider circuit. The D/A can be used as is.

[Steve Anderson]

Steve, it is doubtable that the 180 line system had sync and blanking outside the 4:5 aspect ratio....So is there any data available about that?

Well we'll see what information turns up in the time before I make a start on this, as I said it could well be next year. If it were such that the blanking and syncs were within the aspect ratio then I'll simply turn down the horizontal gain a bit. Maybe the result was a square visible picture? In the two pictures below one does seem to support that, the other (maybe) not.

After "The Brute" I'll be taking a rest in construction of NBTV things, next on the agenda is an Arbitrary Waveform Generator with one MB of EEPROM memory which can be programmed from a PC. No removing the EPROM from the board, no waiting for the UV to do it's thing and no 12/12.5/25V required for programming. It will double-up as a pattern generator for 180 lines (22 frames), 405 lines (4 frames) and 625 lines (1 frame)...all monochrome of course.

Must away, "The Brute" needs feeding.

Steve A.

[Viewmaster]

Here's some info taken from, "Television Today."
Albert.

[Steve Anderson]

Albert,

Thanks for that...sorry, I resized your pic to be a bit more 'display friendly'...

Interesting to note that five of the screen dimensions came out at a 4:3 aspect ratio and two at 5:4. Of course maybe part of the screen was masked by the case so that might not be indicative of what the viewer actually saw. But I think it establishes that it wasn't a square picture.

Thanks again Albert.

Steve A.

[DrZarkov]

The book "Das Fernsehen" states about 10% per line is necessary for synchronisation. That would give a nearly square picture, which looks indeed very much like the "Telefunken" TV-set.

BTW: I like the idea of sepia CRTs. I knew there were green CRTs used in cheap TV-sets, there were those British sets with a pink plastic in front of the screen, but sepia? Or do they just mean the slightly differences in old CRT between the more "blue-ish" picture and the more "yellow-ish" types? I loved our old Siemens "Bildmeister" from the late 1950s with that warm picture. My Philips "Leonardo" in our bedroom has a very good and sharp picture, but it is more "blue-ish". (And of course "too many" lines )

[Steve Anderson]

The book "Das Fernsehen" states about 10% per line is necessary for synchronisation. That would give a nearly square picture, which looks indeed very much like the "Telefunken" TV-set.

I would have thought that the concept of 'aspect ratio' was the format of the actual picture area without including other items like blanking and syncs in television or the audio sound tracks and sprocket holes for film. Certainly in stills it can only be the viewable picture, there's nothing else.

Well thankfully there's an easy resolution to this by providing a horizontal gain control so the viewable aspect ratio can be varied between 1:1 and say 4:3.

Steve A.

[Klaas Robers]

But when you are going to make the pictures for the generator, you should know the aspect ratio, to keep circles round. I had the same problem for the NBTV club-CDs. Then I assumed that the 2:3 aspect ratio (in portrait) was including the sync, so for a syncless signal. The width of the black sync bar subtracts from the aspect ratio, making it more 3:4 than 2:3. The same is for the Baird system, it was anounced as 3:7, but with sync and also the wider lines at the left and the right, it is almost 1:2.

When we see that so many different brands of receivers were available, there should have been a kind of standard. And is should be possible to find that back. That will also reveal the length of the sync and the way vertical sync was achieved. I alway like it to stick to such standards, as they haven't been set up in an afternoon. It is wise to keep the hidden knowledge behind this.

[Viewmaster]

Interesting to note that five of the screen dimensions came out at a 4:3 aspect ratio and two at 5:4.
Steve A.

4:3 has never been beaten. It is compositionally very agreable to the eye and has a nice balance of vert to hor area.

One day, the world might come to its creative senses and dump 16:9 and return once more to the pleasant lands of 4:3.

Just like the story of the Three Bears.......
" 32 lines are much too tall."
"16:9 is much too long."
" 4:3, ah just right for me."

That's my bit on the soap box.

Albert.

[Klaas Robers]

Alber, it depends on the distance to the screen or the size of the screen. Our eyes have several areas and the more to the centre the more sharp you see. The sharpness area isn't circular but somewhat oval. We see a larger part sharp in the horizontal direction than in the vertical direction. I bet this is because the horizon is horizontal.

Now if we look at the definition of our eyes when we look at something under an angle of 10 degrees in the vertical direction, we encounter the same definition of sight in the horizontal direction under an angle of 13 degrees. This is the standard TV definition, we can distinguish details of 1 minute of arc, so 600 lines are needed.

But if we look at an arc of 20 degrees vertical (1200 lines) then the same definition is present in the horizontal direction in an arc of slightly less than 40 degrees. This is where the 16:9 ratio comes from in film when the images were made larger because of better film material or wider films (70 mm Todd AO).

This is the same with TV. For HD-TV you must have a larger screen at the same distance (twice as high). So the picture is larger, vertically 2 times, horizontally 3 times, so 6 times as much picture. And indeed 16:9 in 600 lines is of no use, just a trick to sell new TVs and to make the world ready for HDTV in a evolutionary way.

[Steve Anderson]

After a lull here I've gleaned more information regarding the German 180-line system. The waveforms I'll be using are below.

The upper trace is the 'real' specification, the lower trace is how I plan to implement it based on a 1MHz pixel rate rounding out some of the values making some not quite right, but you'll need test gear to notice it, a human wouldn't.

The centre trace is how I plan to do the frame pulse. Now I know the original used a single broad pulse, but I have modified the vertical such the line timebase doesn't lose lock and require a few lines to regain it.

I estimate this will be an early next year project.

I've every mind to make this dual-standard using Baird's 240 line system.

Steve A.

[dominicbeesley]

Hi Steve,

Have you seen M. Dupouy's latest realisation?

Is this the same system?

Dom

[Steve Anderson]

Hi Steve, Have you seen M. Dupouy's latest realisation? Is this the same system? Dom

Interesting. I didn't realize that the French had also dabbled in 180 lines. It might be the same system, but whatever, it's going to be very similar. 180 lines at 25 fps...not much you can alter there except aspect ratio, interlacing and minor changes to syncs, blanking and the like. The RF modulation however could well be different, both sound and vision.

Interesting to note the hum-bars on the YouTube videos and their instability. Assuming the camcorder used to shoot the videos is crystal controlled (of course) I wonder where and how the 180-line signal was obtained.

A nice active forum, tempted to join myself. Although I lived in Paris for three years it was some 25 years ago, my French is now very rusty.

Steve A.