60 progressive fps to 30fps - best way?

[MarkGrigsby]

Can someone please tell me the best way to convert 60 progressive fps video to 30fps interlaced DVD complient video?

My first thought was to just 'SelectEven()' in AVISynth, thus 'throwing away' half of the frames. But what about instead using 'Weave()' to join each pair of original progressives into a single interlaced frame? Can anyone explain which one would be better and why?

Thank you

[Soopafresh]

Try this, perhaps.

http://neuron2.net/fdecimate/fdecimate.html

http://forum.doom9.org/showthread.php?s=2b00116816e8b27fdeeb818df4f3c0e7&threadid=88201

[MarkGrigsby]

Unless I'm missing something, 'FDecimate' in my example will just throw away every other frame (as I have 60 progressive ones per second). Is this definitely the better way to go, instead of constructing interlaced frames using all the original 60?

[xtreemkareem]

Unless I'm missing something, 'FDecimate' in my example will just throw away every other frame (as I have 60 progressive ones per second). Is this definitely the better way to go, instead of constructing interlaced frames using all the original 60?

Your idea seems to make sense Mark... I'd go ahead and try yours and see how it looks.

[alsyed]

i'm wading into unfamiliar territory, but if you were to weave them together, wouldn't you get funny field effects when you do this, because when you interlace, the fields that make a frame are half the full vertical resolution?

i know, that if i seperate fields of a interlaced pal mpeg2 source which is 720 x 576, i get 2 fields that are 720 x 288 each.

Perhaps you need to do a similar half height resize before you do the interlacing.

As i said, i'm unfamiliar in this technology, so if i am completely wrong, please excuse it kindly

[MarkGrigsby]

Thanks for the replies... Both of them look very similar to be honest, but I still can't make my mind up which is better! I'd rather have some kind of 'scientific' reason to prove it one way or the other!!

Alsyed - When I do the weaving, I'm taking half the lines from 1 frame and half from another, to make my interlaced frame. So it doesn't give any wierd results. Maybe an example would explain better...

Let A,B,C,D,E,F be 6 fully progressive frames (from the original 60fps)

Then I am making a,b,c as 3 interlaced frames (which will run at 30fps) using the following

a=A(evenlines)+B(oddlines)
b=C(evenlines)+D(oddlines)
c=E(evenlines)+F(oddlines)

[junkmalle]

Have you looked closely at your 60 fps progressive source? Most that I've seen have pairs of identical frames. So throwing away every other frame doesn't really lose anything.

For a true 60 fps source, weaving to get 60 fields per second will get you slightly more fluid motions when watched on an interlaced TV. But you won't notice unless you look very closely at just the right type of scene.

[MarkGrigsby]

Thanks - yes, I did check the frames and it really is a truly 60 progressive source.

I'm watching it on a 100Hz CRT, if that makes a diff?

[vhelp]

I would really love to see a sample of this 60fps source
Could you U/L a small clip, mabe 30 frames or less ??

Thanks,
-vhelp 3295

[Abond]

I would go for 30 fps interlaced mainly from practical point of view. Less frames to encode and better quality for the same bitrate. I would resize the frames to half vertical though, using the full frame information.

[MarkGrigsby]

I would go for 30 fps interlaced mainly from practical point of view. Less frames to encode and better quality for the same bitrate. I would resize the frames to half vertical though, using the full frame information.

Not sure I totally understand what you're saying there? Surely it's the same number of frames to encode either way, it's just the content that's different (i.e. whether each interlaced frame is composed from 1 full progressive frame or 2 of these weaved together).

[junkmalle]

I'd stick with 30 fps progressive. The small (perceived) loss of temporal resolution is a small sacrifice to keep the video progressive. Interlaced displays will have no problem with the result. Progressive displays won't have to bob an interlaced picture (with the resulting loss of quality).

[GreatScott]

Which is beter? - I don't know.
But I saw this avs somewhere -

SeparateFields()
SelectEvery(4,1,2) #if bottom field first use SelectEvery(4,0,3)
Weave()