120fps clip to another more 'regular' framerate

[bill_baroud]

hello,

i have got recently a divx5 clip (with B-frame) which is recorded at 120fps ... So i was wondering which sort of frame rate it is (seems just have a lot of frame) and what's the way to reduce the frame rate without lose the sound synchro etc...

i have look to decomb etc, ... or decimate(), but because i don't know what sort of clip is (never seen it before), i don't really know what sort of frame's discard i must use.


If you have any idea ...



thanks fo you help

[DJ Bobo]

120fps??!!
Well, one of two: you're missing something or that file was a bad joke from a bad ass :D
I think,

decimate(cycle=2)
decimate(cycle=2)
decimate(cycle=6)

will be right for you, you'll get 25fps with it.
If you replace decimate(cycle=6) with decimate(cycle=5) you'll get 24fps.
If you omit the third line, you'll get 30fps.
The duration won't change, so don't care about the sound. It will be in synch.

[bill_baroud]

no it's not a bad joke, Properties of file give me something like : frame rate = 119,800fps


and Virtual Dub too in File info :
640x480 - 119.800fps (8432µs)
174844 (24:18)


that's why i ask, it was very strange for me (and the clip have a very small size, and really great quality)

hope the decimate won't break the fluidity of video.

[DJ Bobo]

No no, I don't mean you, I mean the one that made that file is a bad ass :D

This framerate is very irregular, as 119,8 is not a multiple of any regular framerate, divided by 5 it gives 23,96fps and not 23,976

I will then suggest the following to get smooth motion by 23,976fps:
Just open the file in VirtualDub, select direct stream copy, go to framerate, change framerate to 119,88 and decimate by 5

Or if you want 29,97fps, decimate by 4.

You'll have to adjust audio length afterward though.

[trbarry]

A first thing to check might be to open the file in Vdub and step through the records for awhile, one at a time.

Is there a repeating pattern to either duplicates or badly woven frames? If this pattern exists it will often tell what has been done to the file, even if it is not obvious from the frame rate.

- Tom

[bill_baroud]

hmm when you look to the video, the pattern is something like this :

0 : when Vdub indicate [] in the type of frame

0 D D D D 0 D D D D 0 D D D D 0

at the last "0" frame, the image change, so there is 15 frames which are identical.
damn ! in another passage where there is lot of mouvment, the frame change on each "0" frame :/
the new pattern is : 0 D D D 0



if it's a Keyframe, the first frame isn't "0" but [K] ...
the pattern it's the same for what i have see.

it's very strange, because the file size is inferior than the norm (125mb in 640x480 ... for the quality, 150 or 170mb is more usual)

my re-encode have crashed, so i haven't see the result of decimate().

[DJ Bobo]

don't reencode, just make direct stream copy and try first decimate by 5, if it's not smooth, then try decimate by 4