Reduce interlace flicker

[Dieter Moreno]

[Thayalan Paramasawam] “1)Pls explain me what is the purpose the reduce interlace flicker.”

I don’t know what that feature’s purpose is, maybe it is designed to reduce interlace flicker, just a wild guess?

I can’t tell if trolling or serious.

[Thayalan Paramasawam]

Hi Sir,

This is answer……i made post… same question…..now i understand purpose of (reduce interlace flicker)

Thayalan, you’ve asked a great question. However, the answer can have a SHORT or a very LONG answer to it – lol!

OK, real film consists of one complete frame being exposed at the subject/actor, which is then quickly succeeded by another frame, then another frame, then another frame. Now if you can get these to appear in front of the audience at a rate GREATER than the eye and brain can determine as “separate” frames then we will all perceive perfect motion. The “illusion” of flowing realtime motion is perceived by the brain. And this progression of complete frames we can call Progressive

OK, move history forward till we get to the emergence of the wish to transfer these progressive “images” over electric wires.

How are we to do this? Maybe if we could “scan” these still images, code them in some way, and send them as electricity but representing the “light” images we could achieve still or motion perfect flowing images.

Enter John Logie Baird.

Recognizing the characteristics of the photoelectric (p.e.) cell, with its ability to generate electricity from having light shone directly at it, Mr Baird experimented with various ways to get the reflected light from a subject to strike and be apparent on these cells. But there is a limit as to how much clarity and usefulness a single p.e.-cell could then capture. Plus the unfortunate need for extremely powerful lighting source and the ability of the “subject” to withstand high temperatures!

Have many cells, yes, but again there are issues about the size and responsiveness of the surface of a cell. He quickly picked up on the concept of the possibility to breakdown a single Scan and rather have a series of scanned lines, using a spinning disc to literally “scan” the reflected light and use those scanned “lines” to then impinge on the surface of the p.e.-cells and then coordinate them in such a way that what was being seen was a cohesive image: A Face was a Face and not just a series of stupid scanned lines! No small feat this. Followed by the need to “lace” back together these “scanned” lines is crucial in the delivery in the chain of events . . . . . .

Enter the TV age, when the need to transmit these beautifully flowing real-time, perfect motion images over the airwaves and we all start to become familiar with those scanned lines. Apparent at the end of TV tube we now see flowing, and seemingly non-disjointed images, no lines and no image flicker. Two main reasons for this:

1: The scan rate is higher than what our eyes can determine as separate lines, it started with a “viewable” scan-rate of 405 lines per second and then we, in the UK, moved up to 625 per second.

2: The inside end of the TV tube was/is coated with a material that lets the signal glow over a very tiny period of time.

But, but, but – we are STILL only looking at Scanned Lines. Scanned Lines that are processed to become coherently, and cleverly interlaced. If they weren’t interlaced properly, then we’d have a real mess.

Pushing onwards, this Interlace of Scanned Lines carries through to innovation of vision captured by the method of magnetic tape capture and VHS (thank you JVC, and the more fragrant video industries of Hollywood’s neighbours), and we are still okay. We have scanning lines being captured via a rotating spinning drum spinning at high revolutions, that again sends a stream of these scanned interlaced lines to be magnetically laid down on magnetic tape.

See a pattern emerging? Scanning Lines<>Interlace Coherence. We know what we know and we are happy. We n=have a technology that can be adapted and updated to the “New Age” of TV – ahhh… sanity . . . I can watch recorded versions of “Kojak”. Relive the Moon landing ad nauseum and watch Roger Daltry and The Stones on Top of The Pops . . time after time after time . . . what more could I possibly want/need or envision?

All is well with the World!

– But no . . . . .

Enter the Age and the glistening and beckoning domain of the emerging digital era, with what that can provide me with. And once AGAIN we are needing a technology that will adapt what we CAN do to what we WISH to happen (remember the grief the p.e. cell was giving our friend Mr Baird?) We want a perfect motion from a source which is still locked into the analogue remedy Scanned Lines. ( ugh . . Grazie I thought we had done with the hocus pocus of scans and lacing together these darn scanned-line thingies? And then the need to relay these in some way . . what gives now!!?)

Here’s the problem: We have scanned lines that need to be converted to the simple, but reliable binary ZERO and ONES convention. We need to be able to convert what is most definitely NOT binary – ie analogue – to the more adaptable and manipulatable codes of the Computer age. Well this is mostly achieved very well, and achieved by the type of software that is employed: We all have used s/w that codes the scanned lines into digital – into the ONES and ZEROS. This happens mostly quite well; it has supported an industry in the late 20th century and early 21st century to come out with better and more elaborate ways of doing this; has spawned a commercial sector making the best out of a technology that hadn’t come of age – we ALL had to wait . . . R&D had to be paid for and the pay-back of the investors needed to be met. But it has come as major impediment to our surging forward (remember Mr B with his p.e.cell?)

So, if you are still reading my perambulations and wanderings around this subject, we have come to the point where we have scanned, interlaced lines being digitized. Now, WHO on earth would come up with the idea of non-scanned, “still”-progressive images? Images that weren’t made from interlaced lines but were – hold me back somebody images that Progressed full frame by Full Frame – Who in their right mind would then throw THIS into the “£%&!’ mix!?

Well, we got it . . get over it Grazie. So now we have beautifully, scanned and interlaced lines being/needing to be mixed in with non-interlaced-scanned, Progressive still AND interlaced and motion media. Added to which, there’s the possibility that we will change the resolution or shape of the Interlaced media or its mix and fit with the delivery format. In any event, whatever we do to Interlaced footage can/could upset the appearance on screen and certainly through any delivery format – our rendering templates and previewing on screen.

This can result in the badly de-interlacing of interlace to seeing “jaggies” or stepping on footage that we have panned or cropped, or Flickering of Media as it attempts to make sense of the wishes we are imposing on it. Some form of Interlace flicker removal will be needed to “smooth” out the differences as our CODECS try to reinterpret it in some way that appears smooth.

Do I see a weak hand appearing up at the back of the class there?

[Thayalan Paramasawam] “1)Pls explain me what is the purpose the reduce interlace flicker.

2)When can use this option.”

The sole purpose of reduce interlace flicker is to mitigate, remedy, make better all that stuff I’ve said before, and more importantly IF I’ve described it correctly, the reasoning WHY it is appeared in the first place, nearly 100 years ago.

Now, knowing what to look for you will tick-off everybody by sitting on the sofa and mumbling under your breath, as you watch this or that “pro” broadcast with the words “bad de-interlace”, “shocking progressive!”, or “look at those jaggies!” – I do it and often get a pillow thrown at me by my partner, from the other end of the sofa.

OK, I can’t wait for a progressive camera that captures at a minimum of 100 fps and that which I can afford! Better yet, a camera that doesn’t record progressive images at all, but a direct to electron, nano capture jelly!

Look out Logie, it’s coming. Scanned lines? A solution that was needed with the technology and materials that were at hand, then.

You asked a great question. It was a question that deserved a full response. Least of which was to attempt to invite you to recognise the evolution of this technology and the impediments, barriers to getting to a solution.

Dealing with de-interlace and smoothing is yet another slip road off of the Motorway or Interstate – hopefully it will not be with us much longer and when that time arrives I WILL lay some flowers at the graveside of Mr Baird. He had the vision, persistence and belief to carry this through.

BTW, John Logie Baird is buried with his mother, father and wife in Helensburgh Cemetery, I like to think as any of us do today sitting on the sofa, watching towards that same TV.

Thank You
Thayalan Paramasawam