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How do videoscalars like retrotink and ossc work (technically)

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jonpaul:
see history of video codecs and compression.

Yeves FAROUDJA did the pioneering work in 1980s.

https://en.wikipedia.org/wiki/Faroudja

BRAVO to our old friend !


Jon

nctnico:

--- Quote from: tooki on March 30, 2023, 08:54:39 am ---
--- Quote from: bzuidgeest on March 30, 2023, 08:40:46 am ---That sounds simple, just sync to the line. But surely lines, go faster in the digital signals then the old analogue ones. So you would have to look into the future to know what the slower signal is going to do. How do they keep up to each other? I might sound dumb here, but I was asking for basic explanation/tutorial stuff for a reason....

--- End quote ---

Huh? Just how exactly do you think a digitizer works?

I’m sure there are different methods, but I’d expect that the digitizer either digitizes the entire video signal continuously and then extracts the lines from it (either extracting the sync to a trigger from a composite signal, or from separate sync signals), or that it syncs first and then digitizes each line. Either way, the sampling rate is something the designer can choose.

--- End quote ---
No, as Siwastaja already wrote: if the source of the analog signal is digital (which is the case for video consoles), then there will be a finite number of pixels in each horizontal line of the image. If you want the best results, then you'll need to find those pixel boundaries and lock the sampling to these boundaries so you are sampling the pixel values and not the crossover between pixels. You should try and hook up an LCD monitor to an analog VGA output and let the screen 'self adjust'. You'll see this locking process in action (and typically get horrible results when the sampling isn't locked to the pixel boundaries).

tooki:

--- Quote from: nctnico on April 01, 2023, 12:42:18 am ---
--- Quote from: tooki on March 30, 2023, 08:54:39 am ---
--- Quote from: bzuidgeest on March 30, 2023, 08:40:46 am ---That sounds simple, just sync to the line. But surely lines, go faster in the digital signals then the old analogue ones. So you would have to look into the future to know what the slower signal is going to do. How do they keep up to each other? I might sound dumb here, but I was asking for basic explanation/tutorial stuff for a reason....

--- End quote ---

Huh? Just how exactly do you think a digitizer works?

I’m sure there are different methods, but I’d expect that the digitizer either digitizes the entire video signal continuously and then extracts the lines from it (either extracting the sync to a trigger from a composite signal, or from separate sync signals), or that it syncs first and then digitizes each line. Either way, the sampling rate is something the designer can choose.

--- End quote ---
No, as Siwastaja already wrote: if the source of the analog signal is digital (which is the case for video consoles), then there will be a finite number of pixels in each horizontal line of the image. If you want the best results, then you'll need to find those pixel boundaries and lock the sampling to these boundaries so you are sampling the pixel values and not the crossover between pixels. You should try and hook up an LCD monitor to an analog VGA output and let the screen 'self adjust'. You'll see this locking process in action (and typically get horrible results when the sampling isn't locked to the pixel boundaries).

--- End quote ---
I’m well familiar with that. But I didn’t overlook it, that falls under the “sync first and then digitize each line” approach I mentioned.

m k:
Vertical is as equally important as is horizontal.
If it's up scaling it finally has caps to fill.

First there is a film camera.
There film is exposed to light, the whole picture at once.
Keyword here is time.

--A--B--C--D--

Picture taking time start from A and end to B.
Then is shutter time from B to C.
And next picture from C to D.
Object is moving all the time.

Computer picture has no time, if it is not added.
On the other hand, shutter time is lost for ever.

Frame rate adds a 3rd dimension.

So interpolating 2x 2x 2x and there is a single real pixel in the center of the cube.
And copying frames create a temporal disruption.

tooki:

--- Quote from: m k on April 01, 2023, 11:10:26 am ---First there is a film camera.
There film is exposed to light, the whole picture at once.

--- End quote ---
FYI, that’s not necessarily true. SLRs and most other removable-lens 35mm film cameras use shutters with two shutter curtains that move independently of each other, from one edge to the other (mostly vertically, but earlier ones horizontally). This means that exposure begins at one edge of the film and then progressively moves to the other. One curtain is opening, the other closing shortly afterwards. For longer exposure times, the frame will be completely unblocked for some period of time, but for short shutter speeds, the opening curtain is quickly followed by the closing one, resulting in a moving slit, exposing the frame progressively. This can cause effects like a car or horse appearing slanted in the image. While it is continuous (no discrete lines like digital), it is not the whole picture exactly at once.

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