Forced film or IVTC [Archive] - Digital Video Forums

De Joker

30 Nov 2002, 03:40 AM

Is there a difference in quality between using forced film and using IVTC, if both can be used. The reason i'm asking is because i have seen alot of movies lately that can be both forced filmed and IVTCed, but the method with forced film is alot faster.

Thanks, Robert

khp

30 Nov 2002, 04:55 AM

I think that forcefilm will give you better quality, if it can be used. There is always a chance that IVTC will be done incorrectly in some frames.

Enchanter

30 Nov 2002, 08:19 AM

Use the Avisynth "Decomb" plug-in. It has given great results for me.

De Joker

1 Dec 2002, 03:50 AM

Hey Thanks for the replys guys, i'm glad that forced film gives better quality, because its also alot faster than IVTC.

Hey Enchanter how and when do i use the avisynth decomb plugin with gordian knot.

Thanks, Robert

Enchanter

1 Dec 2002, 08:51 AM

how and when do i use the avisynth decomb plugin with gordian knot
Just enable Inverse Telecine from within GK. The AVS script created will make use of the command:

LoadPlugin("decomb.dll")
Telecide()
Decimate(cycle=5)

, which works perfectly well for me (TMPGEnc's IVTC is inferior to this).

De Joker

3 Dec 2002, 01:53 AM

Then i guess i have been using avisynth, because some dvd's could not be forced filmed and had to be IVTCed.

The reason i would prefer using forced film is speed, but if IVTC would give better quality i would use that.

Thanks

khp

3 Dec 2002, 04:57 AM

Originally posted by De Joker

The reason i would prefer using forced film is speed, but if IVTC would give better quality i would use that.

I'am pretty sure that is impossible to get better quality with IVTC instead of force film, for a film encoded DVD.

With force film you read the source frames directly from the mpeg stream at the 23.9x fps that was used to encode the film.

With IVTC you let the Mpeg-2 decoder convert the 23.9x stream to 29.9x fps (using Telecine) and then try to inverse that by matching the fields that look like they belong together.

neuron2

10 May 2003, 03:01 PM

There are at least 2 situations where not doing Force Film is better. 1) When the 3:2 telecining is done "hard". i.e., the source into the MPEG encoder is already pulled down and it is encoded as all interlaced. This is not as uncommon as you might suppose. 2) When there is hybrid material, i.e., a mixture of film and video. For hybrid material, you retain the option to leave the frame rate at 30fps, keeping the video scenes smooth.

There are other situations as well, but those suffice to prove the point.