Tracking with or without fields?

[Boerkez]

Hello,

When I track PAL footage in Combustion I usually get better results when I set the field separation in the footage controls to no fields. But I wonder if the tracking info acquired this way, still is accurate if I later switch back to upper field first in the footage controls.

Can anyone help me out here?

Thanks a lot!!!

Boerkez

[Anonymous]

Usually I defild when I work with footage coming from cameras, but that’s just the way I used to do, dunno if is it the best one, let me tell you that combusiotn has a great operator for defield with 2 or 3 options and to me the best is the merge one.
Cheers

[majik]

Hi

I often find it better to deinterlace the clip first. So if your clip is 50 frames long interlaced, then once its de-interlaced it’ll be 100 frames long. I track my object to this 100 frame clip and then finally interlace the final composite.

[Anonymous]

I think you have that backwards – the original would be 100 interlaced frames, (at, say, 50 interlaced fps) and the deinterlaced version would be 50 progressive full frames (at 25 progressive fps).

[patdawg]

dapeter wrote:

I think you have that backwards – the original would be 100 interlaced frames, (at, say, 50 interlaced fps) and the deinterlaced version would be 50 progressive full frames (at 25 progressive fps).

That’s not true. A true deinterlace will create one frame from each field. What you are talking about is a field merge which takes one interlace frame, and combines the two fields into one progressive frame. Some plugins/apps get the terminology backwards, but the two operations are completely different, and tracking a field merged clip may give you problems as the reference will not be clean. Deinterlacing, tracking, and then reinterlacing is the correct, albeit more time consuming, way to do it.

[Anonymous]

Ohh, OK, I think I got my deinterlace / defield terms a little messed up. I have a DVX-100 so I always try to work in progressive mode to avoid any of the interlace artifacts.

So after removing the interlace do you perform the tracking on the half-height image that results, or are you scaling it back up to the original frame size? Also, does this make the tracking difficult since you’re losing a lot of resolution and color info?

[patdawg]

dapeter wrote:

Ohh, OK, I think I got my deinterlace / defield terms a little messed up. I have a DVX-100 so I always try to work in progressive mode to avoid any of the interlace artifacts.

So after removing the interlace do you perform the tracking on the half-height image that results, or are you scaling it back up to the original frame size? Also, does this make the tracking difficult since you’re losing a lot of resolution and color info?

It doesn’t reduce the frame height…it just duplicates the lines so you end up with a 720×486 progressive frame. I usually deinterlace, track, and then reinterlace.

[Author]

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