What is Decimate used for ?

[Mephiston]

I am trying to back up a bunch of my Box sets. Law & Order & CSI. They all use straight Interlaced Material.

I havn't had a lot of luck encoding interlaced, especially since Doitfast always gets the Field Order wrong for me.

So i have decided to De-Interlace them all.

Deinterlace() works ok, but leaves some ghosting artifacts.
Telecine() works better.

I've seen alot of people use Decimate with telecine, just curious if it's neccesary and will it give better results. From what i can gather it would pretty much make the Material 24Fps instead of 30, then you encode it, then you gotta do a 3:2 Pulldown anyways to get it back to 30. I don't quite understand the benefits of it, or if it is needed at all.

I tried one disk of CSI with it, results were excellent except for 1 fast moving desert scene. It was kinda flickering or something, not sure if Decimate caused this though.

Any help is appreciated.

[malkion]

As a side effect of performing field matching for 3:2 pulldown, Telecide() emits duplicate frames and leaves the clip at its original frame rate. Decimate() detects and removes these duplicates and sets the frame rate down appropriately.

Straight from the tutorial. IMO, it all depends on what you want as your final encode. Deinterlaced, Decimated, all up to you. You can choose to deinterlace your video and leave it at 30 fps, in your case leaving some ghosting, or maybe you'll want to encode it to 24fps with telecide and decimate. In theory this should leave you with a flawless encode. But the source will always determine the final quality.

IMO, you should always deinterlace a video if interlaced, and always decimate a video if 30fps to 24fps. Unless you're in PAL Land, which I'm not. If you have a perfect 3:2 pulldown video, all you need is this:

Telecide(order=1,guide=1).Decimate(cycle=5)

If it's not like that, then there are plenty other experts for your assist. If interlaced, nothing fancy involved then this:

Telecide(order=1,guide=1,post=2).Decimate(cycle=5)

Or you may prefer running a separate deinterlacing filter.

Best wishes. (if your source is hybrid, best read up on the decomb doc)

[manono]

That was good, Malkion. One small correction, though. Since Post=2 is default in Telecide, then both your scripts are identical. If Mephiston plans on deinterlacing, he might be better off using FieldDeinterlace or KernelDeint or some other deinterlacer.

But he doesn't have to deinterlace, since he already said that Telecide works well to get rid of the interlacing. So, evidently this thing is telecined film.

I don't quite understand the benefits of it, or if it is needed at all.

There are big benefits to restoring the 23.976fps progressive frames and then running Pulldown afterwards. By storing 23.976fps on the DVD, you'll have 20% fewer frames when compared to using Telecide(order=1,guide=1) by itself or just deinterlacing it. You'll have a smoother playing video when compared to Telecide, because you'll no longer have all the duplicate frames. You'll have a clearer, more detailed and less blurry video when compared to just deinterlacing it. But the main benefit is that by encoding 20% fewer frames, you'll spread the available bitrate among 20% fewer frames, hence much better quality for the same file size.

[Mephiston]

Ok thanks alot guys.

I will try out Telecide & Decimate on it and see how it goes.

One more question, how can i tell if a video is Telecined or Interlaced.

I tried running Restream on the M2V files, but it just says interlaced.

[Toffypops]

....Why not use SeparateFields command??
Much easier I think..and always gives a perfect result since it only selects one of the fields...and you then half the height afterwards...sometimes thats not needed ..:)

AVISource("C:\MOVIECLIP.avi") <<<<----Location of clip to be loaded
SeparateFields <<<<----splits every second frame
SelectEven or Odd <<<<----Lets you decide to use every first or every second frame
BilinearResize(720,288) <<<<----Resize to desired size

Normal to resize is that if you have a 720x576....:o

A normal resize would have to be 720x288 for a wide screen movie...


Dunno about you other fellows in here..but it works well for me...:sly:

/Toffy :D

[stickboy]

Originally posted by Mephiston
Ok thanks alot guys.

I will try out Telecide & Decimate on it and see how it goes.

One more question, how can i tell if a video is Telecined or Interlaced.Step through frames in the video. If there's a pattern of three progressive frames and then two combed frames, then it's telecined.

If it's interlaced, then each field of each frame represents different moments of time. The only time you'd ever get a progressive frame is in a totally motionless scene.
I tried running Restream on the M2V files, but it just says interlaced. It's reporting the flags from the DVD, but it doesn't mean the source wasn't telecined.

[Toffypops]

aaahh...understand...my bad..still learning..:rolleyes: