video downsampling?

[PeterTheMaster]

hi,

is it possible (if yes: how?) to make a 25fps video out of a 29.970fps video?
like leaving out every 6th frame and dont do this every some hundred frames? (like it works with the leap-years to deal with the real 365.242 days)

if i only change the framerate in virtual dub the video becomes longer, which is not what i want.

is there a tool for this? (i dont want to cut out the necessary frames by hand...)
and: would this decrease the filesize by 17% or are this only my dreams and all these thoughts are nonsense?

regards
Peter

[tenebrenz]

If your source is from a film then you should IVTC to 23.976 fps and speed the video up to 25fps. You will then have to speed up the audio to maintain sync.

If your source is 29.976 true interlaced then I would probably do use avisynth to doubleweave to 59.952 fps and then use the ChangeFPS command to make this 25fps. The audio length will stay the same.

If your source is 29.976 progressive I'd either try the above as for interlaced or try the ConvertFPS function of the new avisynth builds. The audio will stay the same length.

These methods shold result in much smoother playback than simply deleting 1 in 6 frames.

[PeterTheMaster]

my source is progressive.
where can i find a list of avisynth commands?
does avisynth work with virtualdub or only nandub?

[theReal]

avisynth reference guide (http://www.math.berkeley.edu/~benrg/avisynth-reference.html)

Avisynth works with all programs that can handle avi's, even Media Player can open avs scripts.

[PeterTheMaster]

am i dumb or is there no convertFPS in this reference?
seems to be an obsolete version...

[igor140]

Try www.videotools.net for the latest version and documentation of avisynth.

Also, you might find the decimate function in Donald Graft's Decomb Plugin to be helpful. (http://sauron.mordor.net/dgraft/)

[PeterTheMaster]

thanks a lot. i've been to this page twice but you encouraged me to look closer...

[PeterTheMaster]

in the documentaion on videotools it says convertFPS is available since beta7 but the latest version they offer for download is beta 5.
typo?

[movmasty]

>i dont want to cut out the necessary frames by hand !!!!!
well, try foot :D

>you should IVTC to 23.976 fps and speed the video up to 25fps If 29.976 doubleweave to 59.952 fps and then use the ChangeFPS command to make this 25fps.If 29.976 progressive I'd either try the above as for interlaced or try the ConvertFPS function of the new avisynth builds...
...uhmmm.... that is a lot of math

just take the freeware videomach (http://www.gromada.com) ,and set the output framerate as you like.

in fact that little prog does that better than big editors like premiere that are format based, not easy to change fps there.
an example,if you load a vid of 30fps in Ulead,you should use the ntsc30 format,
then if you save at 25fps the vid will be jerky,coz you passed to another format fps(pal).
you should:
1)split audio and video in vdub
2)save the vid at 25fps
3)load the vid in ulead as pal 25fps
4)increase the speed of 20%(120%)to have a movie running at 30fps,but always 25fps(pal)based.
5)save as 25fps
6)merge audio and video in vdub.

regard avisynth ,to pass from 30 to 25 fps you could do this:
SelectEvery(6,1,2,3,4,5)
that is incompatible with the use of temporal soften.

if your frames are 29.97....well, you are in troubles,
i know the way to go, but maybe is more complicated than tenebrenz.

[PeterTheMaster]

my current framerate is 29.970 not interlaced.
why does this mean that i am in trouble?
i did not find an avisynth build which supports convertFPS.
so i used changeFPS, but the result looks kind of choppy although i didnt think the human eye could see such a small difference.

so what is your way to go? i am open for eveything since i now know that this will decrease the size of my final avi file.

[tenebrenz]

I've attached a version of Avisynth that supports ConvertFPS but it'll probably have to be authorized.
so i used changeFPS, but the result looks kind of choppy although i didnt think the human eye could see such a small difference.
I can notice such things nowadays,when watching tv I can tell whether a program is interlaced or progressive and whether it has gone through a standards converter. A friend of mines DVD player outputs NTSC discs as PAL simply by dropping 1 in 6 frames and I find it very annoying.

[PeterTheMaster]

where did you find that version?

[movmasty]

because 30to25 you can cut 1 frames every 6,
29.97to25 you should cut 333 frames every 2000....

if you want to reduce size, do 14.985fps, will work fine

the complicated way would be to change the frame rate to 30 and proceed like above,
then load the audio in sound forge and adjust its durance in accord with the new file

[PeterTheMaster]

no way! i have seen 15fps files before, they suck!
i will try convertFPS as soon as i can download avisynth

[theReal]

I can notice such things nowadaysAfter a long night of encoding I can even see macroblocks when I look out of the window ;)

But really, I know what you mean - it's like you suddenly see the flickering on normal 50Hz TV screens and think "how can people watch tv on such a crappy device?"

[buba king]

Originally posted by theReal
After a long night of encoding I can even see macroblocks when I look out of the window ;)


lol, after a long ecoding batch i start looking for video artifacts when i'm outside, and my dreams are usually about big ugly artifacts jumping around :P

[PeterTheMaster]

@tenebrenz

did you forget to attach the file or does the moderator forbid it?
could you give me a link instead?

[tenebrenz]

Just checked, the attachment is definately there. Unfortunately I can't give a link because I can't remember where I downloaded it from, or how I got there, lol. I even tried a search on google but nothing.

[PeterTheMaster]

cool, its there now. maybe you should give this to doom9 so he can put it on his download page.

[PeterTheMaster]

i forgot to say thankyou. i will post if convertFPS is really better thank changeFPS.

[movmasty]

avisynth-1.0b7a.zip, readme.txt file:
"AVIsynth readme v1.0 beta5"

Then :confused:

[PeterTheMaster]

but convertFPS works.
and the 1pass quality divx5 files even get smaller than
with changeFPS.
im not yet sure yet if i like the result.