Progressive - actions needed, if any.

[pooksahib]

Hi. Please allow me to go back to basics and ask a couple of really stupid questions:

If you watch a vid frame-by-frame (using avidemux, megui, AvsPmod etc) and there's no 'combing' then it's progressive, yes?
Will a progressive vid, with separatefields() applied, always have motion every two fields?
If said vid was made with a camcorder am I right in saying that no correction is required and a simple editor like avidemux is all that's needed?

I ask because of something jagabo said:
"If there's only motion every two fields it's really progressive and TFM() is a better choice than QTGMC() or Yadif(mode=1)"

I googled TFM and, as it relates to cinema film, I can't imagine it being of use with camcorder footage.

Thank you.

[luigizaninoni]

I am not an expert, but this is what I understand:

- you watch frame-by-frame a section of the video (with movement - if it is a static scene you cannot really tell)
- if there is no combing then it is progressive
- if there is combing then it is either interlaced or telecined
- to see if it is interlaced or telecined you watch the video frame-by-frame, but this time with "SeparateFields()" in Avisynth
- if there is motion every field, it is interlaced, so you deinterlace using QTGMC or whatever
- if there is motion every two fields, it is telecined, so you IVTC using TFM (in avisynth) or VFM (in Vapoursynth). If it is PAL, that's all. If it is NTSC you probably need to Decimate as well (but I have no experience with NTSC, so I am not really sure)

[pooksahib]

Thanks very much, luigizaninoni. That makes sense and certainly clarifies what I had been thinking.

[JVRaines]

If it is NTSC you probably need to Decimate as well (but I have no experience with NTSC, so I am not really sure)

Telecine for NTSC creates the equivalent of one duplicate frame out of five, so you must follow TFM with TDecimate to chuck the duplicates and return the material to its original ~24 fps frame rate.

[hello_hello]

Hi. Please allow me to go back to basics and ask a couple of really stupid questions:

If you watch a vid frame-by-frame (using avidemux, megui, AvsPmod etc) and there's no 'combing' then it's progressive, yes?
Will a progressive vid, with separatefields() applied, always have motion every two fields?
If said vid was made with a camcorder am I right in saying that no correction is required and a simple editor like avidemux is all that's needed?

I ask because of something jagabo said:
"If there's only motion every two fields it's really progressive and TFM() is a better choice than QTGMC() or Yadif(mode=1)"

I googled TFM and, as it relates to cinema film, I can't imagine it being of use with camcorder footage.

Thank you.

If you're not seeing any combing then it's very likely to be progressive and nothing needs to be done.

It seems to be a little common for progressive PAL DVDs (not sure about NTSC) to have "out of phase" fields. ie the bottom field of frame A is paired with the top field of frame B and the bottom field of frame B is paired with the top field of frame C and so on.... it will appear to be interlaced because each frame will have combing when you step through frames one at a time, but it's not and the fields just need matching up correctly.

If you open a video with MeGUI's script creator, enable de-interlacing and select Film as the source and TIVTC as the de-interlacing type, it'll get MeGUI to add the TIVTC plug-in to the script something like this:

LoadPlugin("C:\Program Files\MeGUI\tools\avisynth_plugin\TIVTC.dll")
TFM().TDecimate()

That's normally used to reverse telecine NTSC 29.970fps to 23.976fps, but it's the TFM to which you refer. It does the field matching. If you add it to a script like this, that's all it'll do, and if the video is actually progressive, the fields will be matched up correctly and the combing should disappear.

LoadPlugin("C:\Program Files\MeGUI\tools\avisynth_plugin\TIVTC.dll")
TFM(pp=0)

For PAL that's all that's required for out of phase fields. TDecimate() is used to remove one frame in five after field matching telecined NTSC to restore the original 23.976fps progressive "film".
https://en.wikipedia.org/wiki/Three-two_pull_down

If you use QTGMC() or Yadif(mode=1) on video that appears purely interlaced and step through the frames (not fields) one at a time, each frame should be unique where there's movement. If each frame is simply repeated then it's not interlaced and field matching TFM(pp=0) is probably what's required.

It's not very common, but film can also be converted to PAL using telecine (rather than simply speeding it up to 25fps) It's called Euro-pulldown and you'll see a pattern of 12 clean frames and 13 combed frames (or something like that).
https://en.wikipedia.org/wiki/Telecine#Telecine_judder
The original 24fps progressive content can be restored using TFM and TDecimate. Something like this, I think:

LoadPlugin("C:\Program Files\MeGUI\tools\avisynth_plugin\TIVTC.dll")
TFM().TDecimate(mode=7, rate=24)

There should be a bunch of text files in the "MeGUI\tools\avisynth_plugin" folder beginning with TIVTC which explain the various TIVTC settings.