Interlace Problem....pleeeez help me

L

LAfilmaker

Active member
Hey everybody. I saw Michael helping someone else with this same problem under a similar topic but it was left open ended.

Basically my problem is that I have footage shot on 24p normal, F5 and captured at 29.97. As I am editting it looks great on my source monitor, record monitor and my external NTSC monitor. Yet, I exported a quicktime movie with the settings for regular 29.97 footage (because thats what it is after the in-camera pulldown, right?) and I get those "jittery", interlaced frames every 4th frame or so.

Now I know that people will say that you dont notice that on an NTSC monitor. I think that this is only halfway true. An untrained eye will not notice what it is exactly but will be thrown off and attribute it to some "glitch". But a trained eye, like probably everyone on this board here can pick it up without flinching. It is very apparent also when you play the DVD in slow motion or frame by frame.

I really need some help here, I have to show an assembly on a DVD to my client this week and I am not sure if this is going to fly under the guise that "the next one will look better".

Thanks to all in advance!! :)
 
Re: Interlace Problem....pleeeez help me

This will always be the case when editing 24 material as 60 field NTSC. Two out of the 5 frame seqeunces will appear as jitter frames because of the pulldown cadence on what is referred to as the B' and C frames where the cadence in A B B' C and D.

When playing on an NTSC monitor, it is no more noticable than any film based program in primetine television or DVD. The difference will be when stepping through frame by frame. You will see the jitter frames. That is the nature of NTSC and pulldown.

The only real way to deal with it is to work at native 24p with ADVANCED pulldown in Xpress Pro, or NORNAL pulldown captured in any other Avid product that supports NORMAL cadence removal. If you know someone with an Adrenaline, they can capture the NORMAL pulldown and transode to DV25 for you to use in Xpress Pro.

Or, you can always shoot 30p and work in a 30i project and never have a jitter frame becuase all frames are progressive and there is no pulldown cadence.

Michael
 
Re: Interlace Problem....pleeeez help me

I guess perhaps I need to find someone with an adrenaline...but why does the footage look fine after I have captured it but before I have exported it. When I am editting I dont see any of the "jitter" or interlaced frames on my computer or NTSC output.
 
Re: Interlace Problem....pleeeez help me

Hi Michael...thanks again for your response. In trying to come up with someone I know with an adrenaline I quickly came to the conclusion that I don't. Could you perhaps recommend a business or a person who could do just what your described (capturing and outputing back out to DV25 on miniDV) so I can import footage at regular 29.97 and not end up with that jitter in the export?
 
Re: Interlace Problem....pleeeez help me

Hey guys, I know it's not an immediate solution, but Avid just sent out a press release for the new Avid Xpress Pro HD ($50 upgrade fee for current Xpress Pro users) and on the spec sheet it says that it now supports 24p normal and advanced pull down. The upgrade should be made available later this month.

http://www.avid.com/products/datasheets/xpressprohd.pdf

Will that solve the problem?

Chris
 
Re: Interlace Problem....pleeeez help me

It seems as though this is almost like a support group for people having this problem.

Does anyone know why I dont see the "jitter" frame on my computer or on my NTSC preview output when I am actually editting. My projects settings are 30i, just like the export. I don't understand.

Krestofre, is Xpress Pro HD different from regular Xpress Pro. Only because I have Xpress Pro and wonder if the upgrade will still only be 50 bucks.

Azedit, am am actually at this time emailing a person I know at a post house here to see if there is anything he can do for me. I will definately keep you posted on the outcome.

Michael, I just want to make sure I understand what you told me earlier. Based on what you said, I can assume that with an Avid Adrenaline, I can capture and remove the pulldown cadence produced by the 24p "normal" mode and then export back out to DV25 on a miniDV tape at 30i. At that point I can then recapture into my Xpress Pro and 30i and when I export I will not have that "jitter" frame that is plaguing me.

Thanks for all your help guys.
 
Re: Interlace Problem....pleeeez help me

Xpress Pro HD is just a fancy name for Xpress Pro 5. According to the press release if you are a current owner of Xpress Pro (which we all are) then the upgrade to Xpress Pro HD is $50.

Chris
 
Re: Interlace Problem....pleeeez help me

Well, azedit, I couldnt get on an adrenaline for a price that I could afford but I may have sort of a "rigged" fix that will at least get me though this project.

Now I am not the most knowledgeable in this area so my thought process may be incorrect but what I did seemed to fix the problem. Heres what I did.

I thought, what if I try and deinterlace it. So I took about 5sec of the quicktime 30i footage and put it into after effects to try and see if I could do that or maybe pull some other trick out of my hat. When I had the footage in the timeline of after effects I noticed that the footage did not have the "jitter" frame anymore. Keep in mind that this is a project with 30i settings and the footage was interpretted at 30i also. So I just rendered it out into "video for windows" to look at it again that way. Again, no jitter frame. I then dumped it into Encore for mpeg2 transcoding and authoring and watched it on my DVD play. Still no jitter frame and from what I can tell, no degredation of the image.

Like I said, I am no expert on this, I was just a guy at wits end and figured experimentation couldnt hurt.

Michael, perhaps you could shed some light on what transpired, because I really couldnt explain it. All I know is that I went from this :'( to this 8)
 
Re: Interlace Problem....pleeeez help me

The issue is a know issue when dealing with 24 frame material in a 30i (60 field) environment. There are two ways to deal with this - one is to just work at native 24 frames during the editorial process. The de-interlace happens during the capture process removing the redundant fields and creating full progressive frames from the ones that remain. Every frame is now a real frame on disk and while editing. All processing, effects, renders, etc. are done on a frame basis and not field preserving that 1:1 relationship to 24fps thoughout the entire process. At the end, the MPEG2 encoder takes the 24 frames and adds a "pulldown flag" to the MPEG stream telling the DVD player to insert the 2:3 pulldown during play only. But when stepping through frame by frame - you only see the original 24 frames - no jitter. This looks exactly like the Avid timeline (with a Mojo in 4.6 - no Mojo required in 5.0). Stepping through a native 24 frame timeline shows full frame on record monitor and client NTSC monitor. But hitting play inserts 2:3 pulldown on the fly.

If you were to work with the same material in a 30i project (which you are) you do not see the jitter frames when stepping through since you are only looking at 1 field of each frame. What you do see though is a repeat "frame" every 4. So you see a 4+1 pattern. But when playing, all fields are put out to the client NTSC monitor which now has the 2:3 cadence.

In either case, the NTSC monitor during playback has a 2:3 puldown in it. Because the 2:3 pattern inserts 1 field 6 times a second, it is difficult for the eye to see this pattern. The biggest difference is that the native 24p timeline playing back into NTSC has a continuous 2"3 cadence even across edit points. The 30i project will have broken cadence at every edit.

It takes more analysis for a 24p based 30i seqeunce to be de-interlaced into native 24p for the MPEG2 encoding process. There are settings in Sorenson Squeeze to do this, but I have found them to be hit or miss. Hardware encoders do a better job of this since they do multiple pass analysis (like software) but provide better results. There will still be edit points that end up being blended. For eample; an edit point ending on a "C" frame next to an edit point that starts on a "C" or "D". In each case, the NTSC frame contains 1 field from the previos frame...

If it is a priority that the resulting DD have smooth single frame advance, there are only a couple ways to gaurantee this:

Shoot 30p.

Shoot 24p ADVANCED and work in a 23.976p project type.

As far as the After Effects de-interlace, it does have such a de-interlacer since it is crucial for effects compositing to return to the full frames. But you will find blended frames at edit points much like the hardware encoders create.

The best solution is to always work at native 24 (if shooting at 24) so you can provide both a smooth NTSC output, progressive DVD, or film out. That is why 24p is called the universal mastering format.

I hope this helps explain things -

Michael
 
Re: Interlace Problem....pleeeez help me

It does make some more sense at this point Michael, thanks. I have definately learned my lesson and will shoot 24P advanced next time to avoid all this hassle.

Could you perhaps recommend some literature that I can check out on this subject...24p, avid, 24p normal, advanced. I'm just the type of person that likes to get my head around as much information as possible with stuff I am working with. Thanks!!!
 
Re: Interlace Problem....pleeeez help me

DVD Demystified by Jim Taylor for DVD amd encoding. Covers 24 frames, aspect ratio etc.

I'll keep adding to this as I think of more.

Michael
 
Re: Interlace Problem....pleeeez help me

Thanks Michael...I am sure there are several others who will be putting orders at amazon...haha. By the way...what I did in after effects did produce a double frame in this pattern: A,B,C,D,E,E,F,G,H,I,J,J, etc. But I must say I think it looks better that that "jitter" thing.
 
Re: Interlace Problem....pleeeez help me

Hello Michael, LAfilmaker,

Was thrilled to see a post covering my EXACT problem! So I read with great anticipation... Oh my, now I am realizing how serious this error is!

As in LAfilmakers case, My Adrenaline plays a 24P encoded material nicely in a 30i project. I have a few layers (AE generated progressive 30fps )of other video (blends/dissolves/pip efx)throughout this 16 min. project. However, It all plays nicely in the Adrenaline, AND looks identical to the Beta SP tape I made. So, As Michael said, it is the 4:1 effect thats causing such havock in Squeeze? Make sense. But I gave a DV dub to a web programmer (because I was desperate) and he encoded it to the Matrox RT xTreme board --and he had good results.

Basically, Does it come down to this? A hardware encoder will fix the 4:1 pulldown problem?

Also I tried "reduce flicker" in AE 5.5 (don't have 6 or newer yet) and It made little difference other than bluring the field.

Maybe I would have to email you a frame grab to show?

Thank you for any input.

Richard
 
Re: Interlace Problem....pleeeez help me

weird.
I often digitize 24p stuff from a DVX100 in a 30 fps project with deck control turned off (in symphony) and have never had a problem with interlacing. Just pretty 24p stuff living as 30 fps in the same project as the beta sp stuff.
It always looks great considering it's DV.
 
You must log in or register to reply here.
Back
Top