Slow video to half speed

[HartleySan]

I have a video clip that I want to slow down to half speed. Can it be done with Avisynth?

[Guest]

If you need to retain the same frame rate and don't mind dup'ed frames:

interleave(vid,vid)

If not just use AssumeFPS().

You can also do this if you don't want dups and don't mind some loss of vertical resolution (assume source is 25fps):

Bob() # use nice bobber of choice
AssumeFPS(25)

Finally you can use mvtools to synthesize in-between frames but expect artifacts.

[wonkey_monkey]

interleave(vid,vid)

...

Bob() # use nice bobber of choice
AssumeFPS(25)

Doesn't the first assume progressive video, and the second interlaced? If you gave progressive video to the second piece of code, wouldn't you just get the same (minus a little lost detail if the bobber missed it) as the first?

David

[Guest]

Yes, thanks for clarifying. I am unfortunately distracted by other forum developments right now and need to get my head back to fully technical matters ASAP. :)

OP needs to tell us if his video is progressive or interlaced.

[HartleySan]

Sorry about being away so long. Side projects were taking up a lot of time. Lemme look into it and get back with you. By the way, what's the easiest way to see whether a video source is interlaced or progressive?

[Hagbard23]

what's the easiest way to see whether a video source is interlaced or progressive?

;) ...using the forum search... ;)

In short words and roughly simplified:
Yeah - if your video is "combed" it is interlaced (or telecined...depends) - if your video is "clean", then it is progressive. Imagine a picture out of scanlines. If you encounter "Interlacing", then every 2nd Scanline seems to be out of order (in Fact it isn't, but it looks like), especially in motion-scenes. You really see it obiously. If you encounter Interlacing, never forget to set the right field order (AssumeTFF/AssumeBFF/ComplementParity)

BTW: You can also use:

ChangeFPS(<*FPS*>) or
ConvertFPS(<*FPS*>)

See here: http://avisynth.org/oldwiki/index.php?page=FPS

€dit: OMG - Masktools Scripts - yer thinking, betta gunning with cannons on birds or what? To my opinion a little too much..at least for the question:
I have a video clip that I want to slow down to half speed. Can it be done with Avisynth?

[Guest]

Sorry about being away so long. Side projects were taking up a lot of time. Lemme look into it and get back with you. By the way, what's the easiest way to see whether a video source is interlaced or progressive? See question 1 here:

http://neuron2.net/faq.html

Just looking for combing is not always correct. For example, a progressive PAL that has a one field shift will appear combed but is really progressive.

[Motenai Yoda]

from mvtools2 documentation (for progressive video)
best
super = MSuper(pel=2)
backward_vec = MAnalyse(super, overlap=4, isb = true, search=3)
forward_vec = MAnalyse(super, overlap=4, isb = false, search=3)
MFlowFps(super, backward_vec, forward_vec, num=2*FramerateNumerator(last), \
den=FramerateDenominator(last))

fast
super = MSuper(pel=1,hpad=0,vpad=0,chroma=false)
backward_vec = MAnalyse(super, blksize=32, isb = true, chroma=false, searchparam=1,search=0)
forward_vec = MAnalyse(super, blksize=32, isb = false, chroma=false, searchparam=1,search=0)
MFlowFps(super, backward_vec, forward_vec, num=2*FramerateNumerator(last), \
den=FramerateDenominator(last), mask=0)


edit
obviously followed by assumefps(FramerateNumerator(last)/(2.0*FramerateDenominator(last)))

[ficofico]

But, why don't pel4? it's a waste of time or it's really best pel2 over pel4?

[Didée]

"4" is a bigger number than "2". Bigger is better.

It uses much more RAM, and it is much slower. That makes a pretty nice placebo. ;)