Line Twitter
 

Hello, does anybody have any idea why or how i can remove the inevitable line twittering that i get anytime i film something with fine detail (and sometimes not fine detail) on my ex1. It usually happens when i film something black with horizontal or vertical lines but alot of the times it happens on everyday objects like rails posts, leaves, bill board posters. By line twittering I mean that by filming a stationary object such as the head of a Phillips screwdriver, when the image is played back the screwdriver head will have twittering lines on it that seem to move as if I applied a scribble affect to it and ruin the footage.

from the lack of posts on this subject i assume its something i dont need to worry about too much but i would like to know why i always see it. to be more specific, i use vegas 8, monitor on crt and lcd monitors and output to a sd jvc broadcast monitor and domestic tv, the twittering is evident on all screens but less so on my pc monitors. I am shooting using Bill's tcp2 PP and in 1080p 25 HQ.

I haven’t tryed to burn a project off onto dvd yet as my dvd writer is broken and awaiting a new one, so maybe this is something that disappears when the footage is transcoded to sd? Any help would be great.

Thanks

Flickering/twitter is the bane of HD to SD downconvert. There are other posts discussing this problem. Like:
http://www.dvinfo.net/conf/showthread.php?t=116196

The problem is made worse by sharpening the video. To minimize twitter, you can turn off DETAIL in the EX1 menu and sharpen in post(after you downrez). Some people actually recommend adding BLUR prior to downrezzing to mitigate the problem.

This makes me wonder what the big guys are doing to minimize this with hollywood transfers to DVD. No twitter there, and they were for sure not shot is SD ;)

Thanks Bill, it's as i thought...not much i can do about it without compromising picture quality (adding blur etc). I guess it's one of those things one has to live with and do what they can to avoid it aslong as this is a general problem for HD and not just the EX1 otherwise in a heartbeat i would sell this camera and get a canon a1 with a letus because this problem really can ruin a beautiful image and sometimes you dont see it until it's too late.

I have had this problem.

My best result so far is in PAL land filming 720/50P edited in Vegas using project properties set to same and render to DVD Architect wide screen PAL fields set to none . Tried std setting for video 'Good' and also 'Best' does not make any difference. The finished DVD looks very good without line twitter on an LCD tv but some line twitter on a CRT TV. (much worse when filming 1080i or any interlaced format.

Gaussian blur gets rid of the twitter but defocuses the picture.
Currently trying Median effect on horizontral part of pic. Will report back.

Thanks Greg, would love to hear some solid feedback. Do you know if the A1 suffers from such problems?

Should have said vertical part of picture. I am sure I will be corrected.

That's my best result also,BUT with render field set as interlaced,upper field first.1080/50i also looks as good but is a bitch to edit,crap on 2nd monitor whereas 720/50p is nice to edit. I've done loads of experiment with all this

Paul.

seeing as this doesnt seem to be a new problem, how have people been getting round this in the past? Surely theres a way to beat the line twitter problem without the option of getting your footage processed by an expensive video production lab

This was my point I made earlier...
Any ideas?

Don't know if you guys have tried the path thru virtualDub or not. This filter works fairly well..

http://compression.ru/video/deflicker/index_en.html

Great find Bill, however i know i may sound somewhat 'spoilt' but after spending nearly £5000 on this camera i was hoping i wouldnt have to apply filters and lengthy multi-render paths to get a stationary image to stop jumping around. Maybe this is something that comes with working in HD or maybe this is more of a problem with the EX1, im very eager to know this as i believe this is the ONLY shortcoming i would ever consider selling the camera on. I can live with cmos behaviour and what have you but line twitter is something that will affect the type of work i do too much, and upon researching this camera before purchase i never heard of this problem, thats why i assume its more to do with HD rather than the camera

Daniel,

I went through this pain the hard way with my V1E last year - you can do the search for "line twitter" in the V1 forum to see the long discussion of the phenomenon between Bob Grant, Steve Mullen and myself :)

From what you are saying above I'd think that your other displays cannot distinguish progressive from interlaced, and try to de-interlace the signal - hence the line twitter. To check, try to playback the same clip on your PC screen using VLC or Nero Showtime and set Deinterlace=Bob. You will probably see the same twitter on your PC monitor as well...

Anyway, this is purely a display device problem. EX1 does NOT twitter itself!

Well put Piotr.

Piotr, thats all i needed to hear :) Thank you

Veags ain't much cop at rendering mpeg-2 tho is it.

I think part of the problem is that the EX1 is so much sharper than prior cameras. While my HD110 is a huge leap over my old XL2, it doesn't display twitter like the EX1 with DETAIL turned on. I know people like the sharp, native look of the EX1 with DETAIL on, but, if you don't like twitter/flicker, leave the DETAIL off.

Well... yes and no.

As long as your display is not trying to deinterlace, you will not see line twitter from even the highest sharpness. Other artefacts, like edge over-enhancement or noise, yes - but not the typical line twitter.

On the other hand, when you have a twittering display, it will twitter even with sharpness down (perhaps it'll be less visibile, but still there).

When the problem first surfaced with the V1E, Sony adviced to turn down the sharpness in progressive mode from the default 7 (in 0-15 scale) to 3. This of course produced soft image, while the displays that tried to "deinterlace" it still twittered... Therefore, I was using sharpness setting based purely on aesthetic factors, which I also recommend to the EX1 users (for more film-like picture, turning edge sharpening off may be desirable).

Disagree, not my experience, Piotr.

I'm getting the line twitter on both my 13" JVC monitor and my 46" 1080p HDTV. Source is 1080p30 downconverted to SD DVD and played from SD DVD S-Video into JVC and Component into HDTV. I maintained source as progressive when downconverting. The SD DVD feeding the HDTV has a "progressive" switch which did not alleviate the problem.

I'm on a Mac. I tried downconverting in Compressor and Episode and another person I know used Bit Vice with basically the same results.

Line twitter from downconverting to SD is another matter, and involves handling by NLE.

NLE isn't necessarily being used at all for downconversion.

That might be best handled by professional software designed to do that. Episode Pro is about $900 for example and deals with broadcast formats such as MPEG2 Transport streams etc.

The NLE, in my case Final Cut Pro, is working in the native codec but simply rewrapped with a MOV wrapper.

I assume the Vegas users are also working in the native codec.

My progressive HD video looks find on my HDTV. The twitter is only evident in the downconversion. This happens even if everything is kept progressive.

On the Mac, people are seeing this whether using Compressor, Episode or BitVice so it's not related to software used.

Somewhere, some program or device has some "intelligent" algorithm to handle this or we would be seeing this on movies we rent or buy.

The best result so far for CRT TV.

702/50P vegas using same profile.

Rendered to Pal Widscreen rendered upper field first.
Audio AC3 from Vegas timeline.

The first clip was the problem. Outside shot of theatre, sunny railings 'twittering'
The above almost cured it.
Still not perfect but OK.

Everything else not a problem including strobe spotlights.

I had the same issues. I believe it's because DVD's are really only 60i and recognize 24p cadence only in a 60i format. Not 30p. So I was getting weird jitters etc. I changed to 24p, edit, burn to DVD in 24p mode and results? 99% less artifacts and twitters and weirdness. Running Sony DVD progressive scan out the HDMI to 10 different plasmas and LCD's. Same result. Try the 24p at 1/48th to 1/60th of a second. you might like it a lot more.

Now to figure out what detail I need to get rid of edge enhancements... Off, Min, -8? Have to go out and tape some chain link fences and zoom in and out this week.