Deinterlace / Frame Double Digi-8 data
 

Briefly: How can I convert my interlaced video data into frame-doubled progressive video for special effects processing, using only my wits and Adobe products??

As a self-conscious newbie to both the DV world and this forum, I've searched around for ways to do what I need here. Assume I'm using all Adobe software.

I've got two consumer-level DV cameras (make & models are not fresh in my mind...) from which I can capture via direct interface (firewire/DV connections) with my video card, and import to Premiere (v6.5, for now). The data is interlaced, and I believe that the interlace is native to the cameras-- that is, I don't have a progressive scan option in either camera.

The problem is that I wish to do some Star Wars- type effects. This means two things: I need to deinterlace the video, and I need to not lose any data from the images, /LordVader: "NO Disintegrations":LordVader/(sorry). I intend to re-interlace once the effects work is done.

The help in Premiere states that I should be able to simply frame-double the data: convert each field to a frame at double the normal frame rate (and half the vertical res). However when I try that, the deinterlace options that I need seem to always be grayed-out. I've been able to strip out one field or the other, but then I get stuck with only half of the data. I've toyed with the idea of taking the stripped A and B fields down to image-sequences, re-number the files, and then shuffle them back into the proper order in a single file, but that seems overly demanding on my resources.

Thanks for any suggestions,
Andy

Andy,

I have never done this, but I will take a stab at it. I can think of two approaches.

1. Use a standard 29.97 timeline. Drop your footage on the timeline. Right-click on the clip, choose Field Options, Always Deinterlace. Right-click again and choose Time/Stretch, set to 50% and uncheck the "frame blend" box. This will give you double the frames and they will all be rather simply deinterlaced (interpolation). Work your magic and output the result. Bring that back into Premiere and speed it up to 200% with frame blending to get back to something that is closer to the original.

However, one major caveat, Premiere is horrible at deinterlacing, and there may be a quality hit for deinterlacing/reinterlacing in this manner.

2. Create a custom 59.94 progressive timeline. Import your footage, right-click on it and choose Interpret Footage. Set it to No Fields and 59.94 frame rate. Drop it in the timeline and it should be field doubled and twice as many frames. Can't test this right now, unfortunately.

This is a piece of cake in AfterEffects, BTW.

Thanks Mr. Provost,

The interpolation in your first suggestion does cause problems. I will try the second suggestion tonight: it seems promising: I think I've tried similar things, but your first step sounds new to me.

Andy

Tried it. No dice. The highest frame rate available to me was 30 fps in a drop down list, no fill-in-the-blanks section at all. (Version 6.5; perhaps that's my problem...) I was unable to set up a timeline with the doubled framerate as suggested. Thanks again for your response, anyway. I'll probably use your first suggestion, since that would still be better than tossing out half of the data.

Andy,

So, how about a different question? Why do you need to deinterlace? I am assuming to do better "light saber" type effects? Why do you need to reinterlace? You could deinterlace to 30p using something like DVFilm Maker and just keep the footage at 30p. It would have somewhat of a film feeling to it, though not as good as pure 24p.

Josh

I'd really appreciate some dialog on this, thanks for opening the door with your questions...

I 'think' that I need to deinterlace in order to properly rotoscope the blade(s) of lightsabers (tm) in Photoshop: I call this plan "B". When moving, the blades become quite distinctly separate in the A & B fields. Blending those fields leaves an indistinct blur where the blade-reference-stick should be. My plan has been to use heavy lighting and thus fast shutter speeds to minimize the blur in single frames, and then use deinterlaced frames when rotoscoping.

Plan "A" is to avoid rotoscoping altogether, and use a stick-colored (bright white, in the current state of my project) chroma-key to isolate the blade, and send (again, non-interlaced) frames into Photoshop for the glowy effects. This plan cannot work with interlaced/blurry images. Plan "B" means we have to draw in all of the blades by hand anyway, so the blur only slightly complicates that process.

Note that all filming is also being done on a green screen, so I will be isolating several elements from each raw shot, and reassembling them for DVD playback. Thus the re-interlace. I've not really considered the 'film look' effects yet: I've got no budget to speak of, and I'm stuck using consumer level cameras, borrowed lights and volunteer actors/crew.

I'm stuck using Premiere 6.5 for now, but we have plans to upgrade to Adobe's pro-studio package (Premiere Pro 1.5, & Aftereffects) before post-production begins. If Aftereffects has a 'good' deinterlace filter for my purpose, then perhaps I have no problem in the long run. As I've run some recent test footage, however, I can't seem to get an image that is worth the special-effects effort.

My (proposed) technical-kluge solution is separating the fields, using premiere's most basic deinterlace capability (is it 'line doubling'?), into two videos. Export each of those to a sequential bitmap. Then the tricky part: renumber all of those files so I can re-assemble them into a frame-doubled video file-- this can be done with a fairly simple Visual BASIC program. Then export as filmstrip to Photoshop for the magic. I presume that the re-interlace should then be comparatively straightforward.

Andy,

You are trying to do some ambitious things that interlaced video isn't very good at. Ideally you would have a progressive camera capable of 24p shooting, like the DVX100 or XL2. That would give you clean, high-quality progressive images for your rotoscoping.

As far as greenscreening everything. Wow! You know that DV25 (miniDV) is pretty horrible for green screen purposes, right? Very difficult to pull a clean key, or even an acceptable key, because the format just doesn't store a whole lot of color information. To do better keys, you need to jump up, way up, to a better format, like DVCPRO50.

That being said, there are ways to get better keys from DV25. One of them is the deartifact feature of Magic Bullet, which will restore some of that lost detail and give you cleaner keys. It also means tons of processing time to run it through MB, and lots of disk space to save the uncompressed images.

Not saying it can't be done, but you have a lot of challenges ahead of you. Have you done any greenscreen tests yet to see how it looks?

OK, let me just back up and see what we can actually do to get your lightsabers to work...

You may be overcomplicating it. All you really need to do is deinterlace the footage. That means you are going from 60i to 30p. That will give you the nice full frames to rotoscope the light saber in. You can do this in Premiere, as you have seen. It's slightly better in After Effects, but probably not acceptable. Better still, pick up DVFilm Maker. It does real good 60i to 30p, and it will only deinterlace the movement in the frame (the stick), leaving the rest of the frame untouched.

Now, from there you really don't have to do anything to "reinterlace." 30p is basically the same as 60i. You can output it back to tape, you can encode it to DVD, you can do anything you like with it. You don't have to reinterlace, and you wouldn't want to, because 30 will look more film like than 60i, anyway.

If you do go 30p, make sure you create a new 30p timeline in Premiere, with No Fields/Progressive setting. Also tell your DVD encoder that the footage is 30p and it will get flagged as such when it is encoded.

Simple enough? Deinterlace. Edit. Done.

Josh

That's a mouthfull!!

You've made Magic Bullet ( http://www.redgiantsoftware.com/magbulsuit.html ) sound like a worthwhile investment; I'll demand that you get a cut of their sales incentives. ;-) Processing power & hard drive space are expenses easily justified as 'upgrades' to the system we're borrowing. (I've donated heavily to a church AV department in a win-win deal...)

I am aware that the DV made keying less effective: I have noticed some trouble around the edges of my subjects where the green bleeds over. I've solved that by using 2 passes through the chroma filter: one for the bulk of the background to be removed, and a second to clean up the edges. I also plan to use a strong back-light to help keep the green reflection off of my actors.

I hadn't considered just leaving the 30p in place: now that you mention it, that would be a good step toward the film look without extra cost.

Thanks for lending me your expertise!

Andy

Andy,

You actually have more options now than a few months ago. Recently Magic Bullet for Editors was upgraded to version 2, and it now includes deartifacting. That and DVFilm Maker for deinterlacing might be cheaper than Magic Bullet Suite. Check it out. Either way you will be able to go to 30p, or 24p is you want to get into that.

BTW, I think you will find that After Effects has a much more robust toolset for some of the keying/rotoscoping you want to do.

If you can control the green screen spill, that's great. However, even if you had zero spill, the DV codec will still mangle the color around your edges. The deartifacting will help a lot.

Josh

[Arnold Horshack/"Ooh, ooh, Oooohhh! I know!"
 

/Arnold Horshack]

What if I give up on using tape (Digi8/MiniDV that is), and simply feed my PC a direct S-Video signal? The PC has a card that would allow that. Would that bypass the compression (if that's the correct term...) that causes trouble with the chroma-key process?

(Thanks, Mr. Kotter)

-andy

Andy,

Usually not. Depends on how the camera is architected, but usually the DV compressed image comes out of the S-video. Even so, your S-video input will also likely use come compression format on its side.

Josh