interlacing and IVTC

[sidar]

hello all,

i read all guides in doom9 relatin ivtc and interlacing, than decomb guides and decomb help guides and 100fps. i understand somethings, but wanted to be sure that I am right or not, so just please say "you are wrong in here". and i have some questions. because after reading a 100 pages, brain can confuse :)

1- for a pal movie, preview in DVD2AVI, says interlaced, watch closely, if there are horizontal black lines, it is pure interlaced, do deinterlacing (or fielddeinterlace - decomb). (never do IVTC)

2- for a pal movie, preview in DVD2AVI, says interlaced, watch closely, if there are no horizontal black lines, do nothing
3- for a ntsc movie, preview in DVD2AVI, says FILM, do forced film enabled.

4- for a ntsc movie, preview in DVD2AVI, says FILM %95 or higher, can do force film enabled, or do IVTC seperately.

5- for a ntsc movie, preview in DVD2AVI, says FILM, below %95, do IVTC

6- for a ntsc movie, preview in DVD2AVI, says NTSC or Interlaced, preview in virtualdub, if 2 of 5 frames interlaced, do IVTC

7- for a ntsc movie, preview in DVD2AVI, says NTSC or Interlaced, preview in virtualdub, if 5 of 5 frames interlaced, do deinterlacing. (fielddeinterlace - decomb)

so i think it is generally like this. now i have some questions:

a) we can do IVTC with decomb.dll - Telecide(), Decimate(Cycle=5) . so when should we use telecide only in PAL movies, and when should we use telecide only in NTSC movies?

b) isnt it doing IVCT makes the movie pulldown, so if we do IVTC, should we use pulldown.exe?

thanks to you all

note: i dont use gknot, i do dvd to dvdr, with trilight method.

[int 21h]

Originally posted by sidar

4- for a ntsc movie, preview in DVD2AVI, says FILM %95 or higher, can do force film enabled, or do IVTC seperately.

5- for a ntsc movie, preview in DVD2AVI, says FILM, below %95, do IVTC


Except for the inherent speed benefits, you should never use Forced Film. Always use some sort of pattern matching IVTC method otherwise you will notice interlaced frames on many, many scene changes as a result of ForcedFilm. My advice: If its FILM 80% or higher, just use decomb to decimate to 24fps with the provided parameters for recovering a progressive stream.

[sidar]

so can we say all of them are true?

and im really cruios when to use Telecide without decimate, both for NTSC and PAL? or we just dont use it except telecine jobs

[Wilbert]

PAL: telecide(clip) corrects phase shifts and wrong field orders.

[neuron2]

Originally posted by sidar
so can we say all of them are true?

and im really cruios when to use Telecide without decimate, both for NTSC and PAL? or we just dont use it except telecine jobs Your post is full of generalizations and rules of thumb, all of which admit exceptions. Therefore, none of it is true. :) Your point b) is especially silly. And of course DVD2AVI's diagnoses are not always reliable. Finally combing does not involve only *black* lines.

You might use Telecide() alone for NTSC if you have hybrid material and you want to leave the frame rate at 30fps to make the 30fps sections smooth.

[sidar]

thx all for replies firstly,

@wilbert

can you explain some "phase shifts and wrong field orders", english is not my mother language, i didnt got it.

@neuron2

none of it is true --> i felt some was wrong but not all of them :)
but for application side, for pal only fielddeinterlace or nothing, for ntsc fielddeinterlace or "telecide decimate", am I true? i just read a lot of pages, still dont know what to do, yeah I know :stupid:

for general purposes can we say, we dont use Telecide() for NTSC. and for PAL, i dont know :rolleyes:

[neuron2]

can you explain some "phase shifts and wrong field orders", english is not my mother language, i didnt got it.I'll answer for Wilbert, because it assists my answer below.

Consider a progressive PAL clip, with t meaning top field, and b meaning bottom, with capital letters meaning different pictures. First, the raw field sequence:

At Ab Bt Bb Ct Cb Dt Db ...This can be captured in frames like this:


At Bt Ct Dt
Ab Bb Cb Dbor like this:

.. Ab Bb Cb
At Bt Ct DtIn this latter case, there is a one field phase change that causes the frames to appear to be interlaced. But by using Telecide() alone you can rematch the fields and recreate the progressive frames. There are other complications, such as field swaps before and/or after shifting. Read the help file shipped with my VirtualDub filter "Smart Deinterlacer" for a full analysis of these scenarios.
but for application side, for pal only fielddeinterlace or nothingNo. See above.
for ntsc fielddeinterlace or "telecide decimate", am I true?No. Sometimes you might want to leave the frame rate at 30fps, so you'd omit Decimate().
for general purposes can we say, we dont use Telecide() for NTSC.No, not true. We need it for IVTC. If you meant for pure interlaced video (not telecined material), then yes.

[sidar]

wow!

firstly thanks for this detailed explanation. i read it yesterday, than read the smartdeinterlace sceneraios, etc.

1- i understand, that sometimes in PAL videos, there can be phase changes, so with Telecide, we can fix it, and it can be already interlaced with Telecide. but how can we know, that our source has a phase change?

2- i understand we use telecide only for NTSC, if we want frame leave 30 fps. but when? how can we know the source is hybrid, so we want it to be 30 fps?

3- you said:

for general purposes can we say, we dont use Telecide() for NTSC. - No, not true. We need it for IVTC.

but for IVTC, we use telecide with decimate, isnt it?

4- im very sorry, but for understanding i need to get a sceneraio for interlaced, i have samples in robshot and nickys pages for telecine, but can you show me just a interlaced picture in At Ab terms? is it like this? ( i couldnt find a schema for interlaced pictures, in smartdeinterlacer faq there are scenarios but i dont which is what)

proggresive: At Bt Ct Dt
Ab Bb Cb Db

interlaced: At Bb Cb Db
Bt Ct Dt ..

5- in somewhere in your help files, i read that filtering brings quality loss. so If I only watch my reencoded videos in TV (all tvs shows interlaced video true I think), and If I only do DVD-R's, so do I really need to filter my PAL or NTSC video, for IVTC or deinterlace?

[neuron2]

Originally posted by sidar
1- i understand, that sometimes in PAL videos, there can be phase changes, so with Telecide, we can fix it, and it can be already interlaced with Telecide. but how can we know, that our source has a phase change?

2- i understand we use telecide only for NTSC, if we want frame leave 30 fps. but when? how can we know the source is hybrid, so we want it to be 30 fps?The answer to both involves two things: 1) Knowing what these things really mean in terms of fields. 2) Using SeparateFields() to view the individual fields of the clip in question. SeparateFields() is like a microscope; it will reveal all, but you have to understand what you are seeing.

We might leave a clip at 30fps if it has hybrid 24fps and 30fps content and we prefer to have the 30fps parts come out very smooth.

but for IVTC, we use telecide with decimate, isnt it?Yes.

4- im very sorry, but for understanding i need to get a scenario for interlaced, i have samples in robshot and nickys pages for telecine, but can you show me just a interlaced picture in At Ab terms? is it like this? ( i couldnt find a schema for interlaced pictures, in smartdeinterlacer faq there are scenarios but i dont which is what)

progressive: At Bt Ct Dt
Ab Bb Cb Db

interlaced: At Bb Cb Db
Bt Ct Dt ..You're being ambiguous about "interlaced" here. If you mean pure interlaced and not just "combed", then the scenario is that each field is sampled from a different temporal moment, and thus can contain a new picture. Pure interlaced video could look like this:

At Ct Et Gt
Bb Db Fb Hb
5- in somewhere in your help files, i read that filtering brings quality loss. so If I only watch my reencoded videos in TV (all tvs shows interlaced video true I think), and If I only do DVD-R's, so do I really need to filter my PAL or NTSC video, for IVTC or deinterlace? You could leave it interlaced as long as the format you are encoding to supports interlacing. That could include SVCD, MPEG2, or just copying VOBs.

BTW, you're in Istanbul, but you must be Indian. How did I know?