How to gather 2 top fields then 2 bottom fields ?

[Music Fan]

Hi,
I'd like to see how does look a video in which each frame consists of 2 top fields or 2 bottom fields, and not of a top and a bottom field as usual.
I guess the first step with avisynth consists to separate fields, but then I don't know.
The idea is to gather fields 1 and 3 (while they come from 2 successive frames) then 2 and 4, 5 and 7, 6 and 8, ...
weave() is not good for that because it gathers 1 and 2, 3 and 4, ...

[Wilbert]

You need SeparateFields, apply SelectEven/SelectOdd on the separated fields and Weave again.

[Music Fan]

Originally Posted by Wilbert

You need SeparateFields, apply SelectEven/SelectOdd on the separated fields and Weave again.

Thanks, how exactly do I have to apply SelectEven/SelectOdd ?
One then the other, like this ?

SeparateFields()
SelectEven()
SelectOdd()
Weave()

[Music Fan]

Actually no (I answer my own question), if one put SelectOdd() after SelectEven(), the total frames number is divided by 2 (it lacks a frame on two).
But after a few tests, I believe I found how to reach my goal ;

SeparateFields()
A=SelectEven().Weave()
B=SelectOdd().Weave()
Interleave(A, B)

I first tried this ;

SeparateFields()
A=SelectEven()
B=SelectOdd()
Interleave(A, B)

but it seems to correspond to this ;

SeparateFields()
Weave()

[Gavino]

Originally Posted by Music Fan

I first tried this ;

SeparateFields()
A=SelectEven()
B=SelectOdd()
Interleave(A, B)

but it seems to correspond to this ;

SeparateFields()
Weave()

No, it corresponds to just SeparateFields() on its own, because

A=SelectEven()
B=SelectOdd()
Interleave(A, B)

effectively does nothing. (It divides the clip into two then simply puts it back together again.)

[Music Fan]

Right, I confounded some tests I made, I should have seen this before to write it.

edit : I believe I meant that ;

A=SelectEven()
B=SelectOdd()
Interleave(A, B)

corresponds to ;

SeparateFields()
Weave()

[videoh]

It's a stretch to say they correspond, beyond the fact that they both do nothing. One creates two clips and the other doesn't.

[feisty2]

you might need separaterows and weaverows functions

[Music Fan]

Originally Posted by feisty2

you might need separaterows and weaverows functions

What's the difference compared to the script I gave ?

[StainlessS]

Does this work ?

mpeg2source("d:\vob\XMEN2.d2v")

SeparateFields
E=SelectEven.AssumeFrameBased.SeparateFields
E_A=E.SelectEven
E_B=E.SelectOdd

O=SelectOdd.AssumeFrameBased.SeparateFields
O_A=O.SelectEven
O_B=O.SelectOdd

Interleave(E_A,O_A,E_B,O_B)
Weave
AssumeFieldBased
Weave

EDIT: I may have misunderstood requirement, above intended to have 2 top fields, then two bottom repeated.

[Wilbert]

Something like the above should work. Shorter would be:

c = mpeg2source("d:\vob\XMEN2.d2v")
f = c.SeparateFields().AssumeFrameBased() #t1b1t2b2t3b3... #not sure whether AssumeFrameBased() is necessary
f.SelectEvery(4,0,2,1,3) #t1t2b1b2 t3t4b3b4 ...
AssumeFieldBased()
Weave()

[wonkey_monkey]

Did you miss a weave() at the end there, Wilbert?

Annoyingly that script is exactly what I was going to suggest, but didn't want to look foolish if it turned out I'd got it wrong

[Wilbert]

Did you miss a weave() at the end there, Wilbert?

Yes doctor Thx. I corrected it above.

[Music Fan]

Same question than above, what's the difference between this script and mine for the output ?
I post it here again ;

SeparateFields()
A=SelectEven().Weave()
B=SelectOdd().Weave()
Interleave(A, B)

[Wilbert]

I think they are the same.

[Music Fan]

Ok.
There is something strange in Virtual Dub with my script : the duration is divided by 4 compared to the original video while the framerate and the number of frames of my script are identical to those of the original video.

edit : that's an error, actually the duration is the same but I realize that ffvideosource does not detect the good framerate, thus I have to add assumefps(25/1), which I did in my main script but not in my first script containing only one line (ffvideosource ...).
The source is a TS file containing mpeg-2 in 720.576, ffvideosource has maybe a problem with ts files.
If I don't add assumefps(25/1), the detected framerate is 5.89 fps.

[bxyhxyh]

It seems you found the answer. But you can try this

SeparateRows(4)
SelectEvery(4,0,2,1,3)
WeaveRows(4)

[Music Fan]

Originally Posted by bxyhxyh

It seems you found the answer. But you can try this

SeparateRows(4)
SelectEvery(4,0,2,1,3)
WeaveRows(4)

The result is very different than my script which makes the video shake, not yours.
And the frame number differs in 1 case ; if I i add trim(100,0) (= from 100 to end) in both scripts, I get 6832 frames with mine, 6831 with yours.
But if I add trim(100,199), they both get 100 frames.
If I don't use trim, they both get 6931 frames.

But this is a ts file recorded on tv, I should try with another file.

[Music Fan]

@ bxyhxyh ;
I tested with another file, there is clearly a problem with your script which seems to blend fields, not mine.
You can see it by adding SeparateFields() at the end of the script.

[Music Fan]

Here is an interesting exercise, begin the script with this to see big numbers on an interlaced video, you don't even need video, thanks to BlankClip function ;

BlankClip(length=100, width=720, height=576, fps=25, color=$000000)
ShowFrameNumber(size=400)
separatefields() 
selectevery(4,0,3) 
weave()

This way, each field has its number.

Then add bxyhxyh's script, then mine, add SeparateFields() at the end, forward frame by frame in Virtual Dub and see what happens

Here are the complete scripts ;

BlankClip(length=100, width=720, height=576, fps=25, color=$000000)
ShowFrameNumber(size=400)
separatefields() 
selectevery(4,0,3) 
weave()
SeparateFields()
A=SelectEven().Weave()
B=SelectOdd().Weave()
Interleave(A, B)
SeparateFields()

BlankClip(length=100, width=720, height=576, fps=25, color=$000000)
ShowFrameNumber(size=400)
separatefields() 
selectevery(4,0,3) 
weave()
SeparateRows(4)
SelectEvery(4,0,2,1,3)
WeaveRows(4)
SeparateFields()