Can anyone tell me, when using the 405/72i interlaced electronic/mechanical color hybrid output mode does this assume a certain geometry of the colour segments on the filter wheel? If so which?
For example:
[
attachment=19133]
Peter
I can't imagine that it does anything other than put out the 3 frames sequentially. In the original CBS system the actual transmission would have been dependent on the camera's colour wheel.
That's what I thought. So it may be difficult to create a colour wheel that cleanly transitions between segments using the Aurora output signal.
Peter
Surely not, Peter.
It will only be necessary to get the wheel synchronised to the scan correctly.
If you look at the diagram you posted, it is the start of the scan and the entire line falls within the filter segment at the top of the screen. The wheel then rotates as the scan progresses downwards and, when it reaches the bottom it will have exactly the same relationship to the filter wheel as shown except that the entire segment will have rotated and it is the next segment which is now waiting at the top for the scan to restart.
For that to work, the Aurora will need to change colour with every field. If it only changes at frame rate, as suggested by Jeffrey, two consecutive segments of the wheel will need to be the same colour - effectively, replace with three double size segments.
(26-10-2019, 07:15 PM)Terry Wrote: [ -> ]Surely not, Peter.
It will only be necessary to get the wheel synchronised to the scan correctly.
Hi Terry,
Yes, I see no problem if the camera uses the same wheel geometry but for someone attempting to use the Aurora signal with a vintage receiver with a Goldmark wheel I would think it would not be easy for the Aurora to simulate the correct signal.
Peter
(26-10-2019, 07:54 PM)Geordie McBoyne Wrote: [ -> ]Would it be possible to display the sequential field system on any tri-colour CRT?
From Wikipedia: https://en.wikipedia.org/wiki/Field-sequ...lor_system
Geordie McBoyne.
I don't see a problem. The RGB channels of the RX would have be switched in sync with the RGB signals.
(26-10-2019, 08:51 PM)peter scott Wrote: [ -> ]Yes, I see no problem if the camera uses the same wheel geometry but for someone attempting to use the Aurora signal with a vintage receiver with a Goldmark wheel I would think it would not be easy for the Aurora to simulate the correct signal.
Peter, it makes no difference whether the sequence is mechanically or electronically generated. The result is still a sequence of complete fields in an RGB sequence (although the order doesn't
have to be RGB).
As I explained before, each field will be filtered, from start to finish, though the same filter section.
I'm assuming that the segment sequence is RGBRGB or whatever matches the transmission sequence.
If the Aurora output is
frame sequential, the segment sequence will need to be re-arranged to RRGGBB.
I can't see what your difficulty is apart from this. If you still have a problem, can you explain exactly which part of the process you don't understand and I'll attempt to sort it out - assuming that I haven't made a mistake in the first place!
Hi Terry,
[
attachment=19137]
My difficulty is in thinking about the instant in time captured in the picture above. I'm quite happy that the Aurora can generate a sequence of RGB frames each reproducing the appropriate luminance for each colour but let us suppose that our B&W screen is displaying the red image and that the receiver filter wheel above has its red filter covering the area below the arc. The next filter will be green and so the area above the arc will be displayed to the viewer through a green filter even though they are still looking at a red frame.
This presents no problem when the luminance information comes from a camera whose filter wheel is precisely in phase with that in the receiver because the transmitted frame in the instant captured above will contain information appropriate to parts of both green above and red below the arc separating the two colour filters simultaneously.
As it happens, I suspect my interest in this is now purely academic. I had mistakenly assumed that the Multi-standard hardware was the same as that for the CBS Color Converter and that the only difference was a firmware change but I see now that they use different Xilinx chips so I assume that the CBS Color will probably not be available to me.
Peter.
Hi Peter,
I think I can spot the cause of the confusion. You are thinking in a digital world but what you are discussing belongs firmly in the analogue world.
Only one spot on the CRT is illuminated at a time. The light output of that spot of phosphor starts to diminish rapidly as the electron beam continues to sweep across the screen and we rely on persistence of vision to give our brains the mental illusion that the whole screen is illuminated evenly - but it isn't.
Take a look at your drawing in a different way:
[
attachment=19139]
This is the instant that the last line of the red field is written. There is enough filter area above that line to ensure that the light from the decaying earlier lines stays red.
There is then a pause for the field blanking interval when nothing is written but the filter continues to rotate so that, by the time that the first line of the green field is written, the entire length of the line will be behind the green filter.
Does that help?