convert fps 23.976 -> 25

[Kwark]

I'm going to reencode an avi source to mpeg2.

The source avi is a 23.976 fps clip with mp3 audio.
My target is 25fps properly resized video stream and corresponding ac3 file.
The resizing and ac3 conversion (using besweet) is no problem, but I'm not sure how to get the best result with the fps conversion.

Any gurus here who can tell me the best way to do this?

[Boulder]

Use AssumeFPS(25.000) in your script. It will only speed up the video and that's the proper way to do the conversion.

[Dreassica]

just do assumefps(25) in avisynth and speed up audio to match.

[edit] Boulder just beat me to it :P

[Kwark]

Maybe I'm wrong, but isn't AssumeFPS(25) a nasty solution?
After all, it's no 25fps video stream, but almost 24.. won't that give bad results?
Isn't a real conversion better?

[Manao]

Why do you think Pal movies are shorter than NTSC one ? Because they are speed up from 24 fps to 25...

Anyway, try, you'll see that you won't notice the speed up ( you can't tell whether a car runs at 24 are 25 mph, and it's the same thing )

[stickboy]

Originally posted by Kwark
Maybe I'm wrong, but isn't AssumeFPS(25) a nasty solution?
After all, it's no 25fps video stream, but almost 24.. won't that give bad results?
Isn't a real conversion better?So you'd prefer blended or duplicate frames?

[Mug Funky]

unless you know the movie's soundtrack extremely well, or have perfect pitch, you wont notice. and seeing as you're already going lossy->lossy for the audio, there's no reason not to speed it up as well.

however, a blend conversion such as convertfps(50).separatefields().selectevery(4,1,2).weave() is quite feasible at DVD bitrates, if you're watching it on an interlaced CRT (a TV:)).

this will preserve the speed, but hurt compression a great deal. still, in some situations it's desirable (hybrid anime, or unwillingness to re-encode audio). if you're doing this, remember to encode interlaced! (alternate scan, top-field first, and any other interlacing options your encoder has).

most of my store-bought PAL dvds are sped up from film. if you're used to seeing it that way it's fine. only time you get problems is with musical stuff (the pitch shift is significant).

[Dreassica]

With tools such as soundforge u can speed up audio while preserving pitch.

[Wilbert]

http://www.avisynth.org/TimeStretch

[JanBing]

For a blended conversion of my Brisco County Jr. SVCD-files (NTSC) to PAL DVD I used this script:

v = AviSource("E:\brisco1.avi").AssumeFPS(23.976).ConvertToYUY2.ConvertFPS(50).ConvertToRGB

v1=v.SelectEven
v2=v.SelectOdd.Crop(0,0,-0,-1).AddBorders(0,1,0,0)

v3=interleave(v1,v2).VerticalReduceBy2.Lanczos4Resize(720,288).AssumeFieldbased.weave

return v3

I did this instead of simply speeding the clip up because I wanted to have dual audio for the DVDs (English and German), and the speed of the SVCD-audio already matched the speed of my German PAL-VHS-audio. So it would've been necessary to speed up both audio-tracks (even the one that already came from a PAL source).

[scharfis_brain]

janbing, better use this way:

AviSource("E:\brisco1.avi")
AssumeFPS(23.976)
ConvertToYUY2()
ConvertFPS(50)
lanczosresize(704,576)
assumeTFF() #for TFF-output, assumebff() for BFF-output
separatefields()
selectevery(4,0,3)
weave()


but better use changefps(50)
it will introduce two slight stutters per second, but it will be much better compressible.

[JanBing]

I've tried several methods... I compared all of them on my TV-set, and the one I used turned out to look best, and to be the smoothest in terms of motion (that's why I won't use your method... stutters are unancceptable for me). Compression-wise I didn't have any problems (2-pass VBR at 2700 kb/s average turned out to look great, with no major compression-artifacts visible), 180 minutes fitting on one DVD-R-4.7

EDIT: What exactly does the SelectEvery-command in your script do? I thought it's used to tell AviSynth which frames to show... and SelectEvery(4,0,3) would cause a frame order of 0,3,4,7,8,11,12... doesn't it? Why would I want the other frames to be left out? I might sound dumb here, but maybe I haven't understood the SelectEvery command fully...

EDIT2: Forget it, got it... silly me... it's used to get from 50fps to 25fps (actually from 100fps to 50fps and the weaved down to 25fps).

[scharfis_brain]

with convertfps(50) (like in my script, I posted above), the motion will be as fluent as yours, but my method delivers mor resolution (definition) than yours and a correct spatial field alignment.

[JanBing]

I see... you're right... though I've already finished 3 of the 7 DVDs, I guess I will use your method for the rest.

(By the way, PAL-DVD has TFF, right? I can't seem to memorize that...)

[scharfis_brain]

the process from 23.0976 to 50 fps is made with progressive frames.

50fps -> separatefields produces 100 fps, with every two fields containing the even and the odd lines of each frame.
this results in 100 fps.

to reduce this to correct interlacing, we have to select the right fields.
this means, you have to choose the even lines from the even progressive frame and the odd lines from the odd progressive frame.

this leads us to selectevery(4,1,2) oder 4,0,3

an addidtional weave creates the full height.

[JanBing]

Yeah, I got it now... and I'll use it *g*

[Johnny_Deep_Down_Below]

Just use TimeFactory from ProSoniq and AssumeFPS(25)!

The converted movie's duration is exactly 95.904% (=23.976/25) of the original one, and you won't notice anything.

But you will always note duplicated/interpolated frames!!!

[Mug Funky]

hehe... i tried speedup on Eva once. i guess i know the theme song too well, because the chipmunking made it awful, and an alternate version i did using timestretching was perceptibly too fast - the opening theme has a very fast tempo as it is, and sped up even by ~1 fps was enough to have me almost in fits.

maybe if i jack up on caffiene before watching a speedup my brain will be synchronised with it. i might actually try that one. people's voices are higher after coffee, after all (i had to mix/master radio interviews, so believe me i know).

[scharfis_brain]

I assume the speedup or no-speedup discussion is depending on the needs of the people.

the one isn't that much sensitive to blends and/or jerkys
and
the other one isn't that much sensitive to a audible speedup (even if timestreched/squeezed)

I am counting among the 2nd kind of people.

[Boulder]

Originally posted by Mug Funky
people's voices are higher after coffee, after all (i had to mix/master radio interviews, so believe me i know).

I've noticed that everything sounds a bit higher when I have a hangover:confused: I can tell that from the way the PC beeper sounds when I boot the computer.

[scharfis_brain]

I tend to recognize music sounding at little higher-tone-level at higher volumes.

if I use headphones with normal volume, everything is fine.
But when I turn on the volume to near-max I hear everything a little higher.
I don't know why this is like it is. Is this due to psychoacoustical reasons?

[IgorC]

How can i convert 29.9 to 23.976?

[ObiKenobi]

Originally posted by IgorC
How can i convert 29.9 to 23.976?

You need to do an IVTC using a plugin like Decomb (this is assuming that your source has been telecined from film).