Converting 29.97 fps to 23.976 + pulldown to 29.970 !!

[vhelp]

I have a question for all you fps gurus out their.

This may sound a bit crazy but it does work for me w/ little tweaking.

I'm experimenting w/ framerates in my DV sources (home footage)

Here is the nity-gritty of what I'm doing:
* 29.97 fps to 25 fps to 23.976 w/ 3:2 pulldown to 29.970 fps


Now, for the history. . .
I've ben toying around w/ converting the 29.97 fps to 25 fps and have ben
very successful w/ it. But, I haven't thoughly tested it out on a TV set yet.
But, so far, it seems to be fine on my PC - - audio seems to be in sync

However, I'd like like to turn it up a notch. Yes. I'd like to snow take this
same converted 25 fps and (make believe it's film) and try to convert it to
23.976 (operating under the illusion that I'm converting PAL film to
NTSC film) I know.. kind of crazy. But, I did do this in two way already, and
I seem to feel it's not too bad - - no noticable studder or strobbing that I
can tell at the moment (though that comes after hours of debugging and
testing)

The applications upon using this technique..
Well, it's rather simple. If I'm shooting scenery or people talking, and as
long as I control the panning just right, (smooth motion that is) I can
get away w/ this double-convert technique. I know it does sound crazy in
all, but it does work, IF you do it right, EVEN THOUGH your source is NOT
film. I've read in many website (through my researching) that there ARE
techniques to converting your DV footage source to 23.976 w/ pulldown to
29.970 fps through the use of trickery, of which I haven't quite mastered
or fully figured out yet. I think I'm close or getting their. But, I may need
some additional assistance (if you or anyone else are keen to this fps thing)

My main concirn is the audio going out of sync when I perform this:
* 29.97 fps to 25 fps to 23.976 w/ 3:2 pulldown to 29.970 fps

If I could do a:
* 29.97 fps to 23.976 w/ 3:2 pulldown to 29.970 fps

and skip the 25 fps part, I would. But I haven't started figuring out that
one yet. I started working w/ converting 29.97 to 25 fps and made up w/ great
success. But, now I thought, if 25 fps looks good (smooth) and audio is in sync,
then why not go the extra mile and if I can convert to 23.976 w/ 3:2 pulldown
to 29.970 and all. It's a bit crazy but why not try anyways!!

I'll try and fill in the gaps if there are any.


Thanks for any tips or pointers :P

From the desk of,
-vhelp

[FulciLives]

What method (in detail please) are you using to go from 29.970fps to 25.000fps?

If I know how you are doing this step then maybe I can help.

- John "FulciLives" Coleman

P.S.
I've heard of a lot of people in the USA using PAL camcorders for this very reason ... it is easy to convert 25fps PAL to 23.976fps NTSC with 3:2 pulldown.

[vhelp]

hi Fulci..

Thanks for taking an interest to my post.

Yeah, here's the script that I use, and I must say, its quite smooth
when I play it (after I convert to MPEG-2) (see below)

Please note, I have a pretty good de-interlacing technique that I am now
experimenting with on my 29.970 fps DV footage. I have it to an acceptable
tolerence level, but I'd like to apply it to the 25 fps convertion (see below)

The problem that is, that this 25 fps (based on the selectEvery(4,1,2)) it does
a re-interlace of the source and even if I apply my de-interlace routine on the
25 fps, you can see the frames blend every two or three or something like that.
So, I first want to try a few other things out before I go even mad'er into
the de-interlace.

Please note, the script below is perfect (imo) but, I'd like to push it up a notch
and go 23.976 but w/ 3:2 pulldown which brings the fps back up to 29.970
but perhaps w/ a few tricks w/ field matching or swaping, I could probably
get away w/ it on some footage, IF I shoot my cam a certain way (of which
will have to be fine-tuned to be successful of this trickery conversion) For
something like this, this type of crazy conversion just might do!!

Without further due..

Thanks again all, from the desk of
-vhelp 2027

## Converts (NTSC 29.97 fps) DV footage to (PAL 25 fps) ## 

 x="d:\01.00.vdr"

 segmentedAVISource(x)

 SeparateFields()
 Weave()

 ConvertToYUY2()
 ConvertFPS(50) # or ChangeFPS(50)

 SeparateFields()
 SelectEvery(4,1,2)
 Weave()

[adam]

I think this is a futile project. You can't IVTC pure interlaced material and any other method of framerate conversion is going to throw out temporal information. There are only two reasons to do an IVTC. First is to free up bitrate, but unless you are encoding to a very low bitrate than the jerky motion is going to be far more deterimental than any possible artifacts caused by a lack of bitrate. The second reason is to have progressive footage which encodes better. Well, assuming an IVTC is not possible, you will get much better results just by deinterlacing.

If you've got the bitrate to spare keep it 29.97fps interlaced. If you don't have the bitrate deinterlace to 29.97fps progressive. Under no circumstances will 23.97fps progressive look better than either of these other options assuming you have pure interlaced sources, which you do. The same goes for converting to 25fps progressive or interlaced. You are just trying to make the film something which it is not. You can't undo how it was shot.

If you do decide to try to convert your 29.97fps material to 23.97fps material then there is no reason to adjust the audio. These two framerates will have the exact same playtime, so the audio will sync either way.

[vhelp]

Hi Adam..

Thanks for your input too

Yeah, I've know this, and I've ben there too. I do understand the issue w/
"temporal loss" and such, but I've ben pounding at this for a while now. And,
I've come to a close juncture. It's very tricky, but can be done, but as you
said, "jerky motion" is evident, especially when you factor into the equation
the human error of holding the cam in their hand/arms while pannig and
jerking the cam around. Although you don't notice this as much during a
direct connect (cam to tv) you DO when you encoded it to MPEG (it's much
less forgiving in quality) I've come to a point, that after careful experiments
and another, that if the cam is properly panned, (smooth motion) the jerks
and studders seem to go away. This require a learning curve in CAMing
technique, of which I am to discover. I haven't quite ruled out strobing though.
But, I'm not gonna craz myself over this just yet. One thing at a time for me.
Anyways..
So, yes, I do understand this issue w/ pure DV interlaced sources

Ok, FYI, as I sort of stumbled on to something in this 25 fps conversion.
When I found that the 25 fps could come out soo good and smooth and w/out
any jerks and studders, I did some rather arkayek (spelling) scripting, between
AVS scripts and vdub scripts.
I found that I could jimmy a few vdub script -> AVS -> vdub -> AVS into
TMPG using a final fps of 23.976 and add in a 3:2 pulldown and my source
would not really studder at all in some scenes. I narrowed it down to the
way the cam is panned, and how objects moved. Then, I did some crazy
tests w/ my cam and used a tripod and rigged it to an arm that allowed it
to pan accross. I found that when the cam was moved by human error, it
highlighted the jerks, but when the cam was controled by a steady and constant and smooth motion, the jerks weren't so apparent if at all. Although
this sound strage and futile, IMO, it warranted some futher experiments
hence, here I am asking for additional help/tips etc.

Please remember, I'm experimenting on this. I dont' plann on doing this
forever, (unless it turns out successful) But, in the mean time, while I got
a cam, and some time to waist on such ideas, I'll continue w/ this
experiment till I'm either tired of it, or turns out to be pointless.

I've ben able to convert my DV footage to 23.976 and use 3:2 pulldown w/
29.970 in various scenarios but this proved (as you said above) that this
causes jerks and things. Yes. Correct. But, when I first converted this
source to 25 fps and THEN convereted it to 23.976 w/ 3:2 pulldown, things
got a little better So, I started addtional testing. Anyways...

Note, I'm not trying to turn my DV footage into Cinema quality. I'm hoping
that some of this will help in my divX conversion of from DV or even MPEG-2
encodes etc. It's my hobby to tinker in these areas and still have
fun at it.

I will take your advise on the audio issue though. That's something I didn't
quite understand in this elaborate process of mine.

-vhelp

[FulciLives]

I don't have a DV cam ... only a Hi8 cam ... and it's away in storage someplace.

Any chance you can post a SHORT sample clip somwwhere that I could attempt to download. Maybe like a 10 second clip.

I mean original raw 29.970fps DV cam footage.

Then I can play around with it and see what I can come up with.

Also I suggest you ask Xesdeeni for help on this as he is the king of framerate trickery in my book.

- John "FulciLives" Coleman

[vhelp]

@ Fulci..

Again, thanks for your interest.

I'll see what I can do to come up w/ a short 10 sec .avi for you (non-filtered
of course)

Well, maybe Xesdeeni is reading this and can respond. I'd really don't
want to have to look him/her up and all. I'm getting ready for bed because
I'm completly bushed !! pfew!! Yeah, work is getting more tiresome these
days

Thanks all for hearing me out on this

From the desk of,
-vhelp 2029

[adam]

When you say you are getting acceptable results if you film it just right with a tripod... Are you just panning really slowly? If so then you are taking many samples of each shot (new shot everytime camera moves.) So when you randomly decimate frames during your conversion, you don't notice the lost temporal information because for every lost frame there are maybe 20 or so just like it. The problem is that this only works on stationary objects. If you try to film something in motion it will never work. You can slow down the speed the camera moves, but you can't slow down the speed that objects in the camera's view move.

Also, just to clarify. When you convert your film to 23.976fps you are not reconstructing whole frames, you are simply blending fields. This no different than using a blend deinterlacer on your 29.97fps interlaced footage to make it 29.97fps progressive. Blending fields makes for a blurrier image. The point of IVTC'ing something is to return it to its progressive state. DV, at least in a regular consumer's budget, never is progressive to begin with. An IVTC really accomplishes nothing. I know you are just experimenting, but there is no way this could ever look better than keeping it 29.97fps no matter how you film. Sorry to be such a party pooper, but its true.

[vhelp]

.
.

I know you are just experimenting, but there is no way this could ever look better than keeping it 29.97fps no matter how you film. Sorry to be such a party pooper, but its true.

Yes, exactly I agree.. and also, I'm just experimenting.

In addition to my regular cam features...
There are other areas that I'm discovering as well, that might help me out
in this experiment. Well, anyways, I'm exploring all possibilities.. anything
that might give me an edge (for the time being, during this testing) Well,
I'm still trying to re-trace my steps that left me to this belief (or wild goose
chase hehe) but I'm pretty pooped out, and ready for bed.

Thanks for taking the time to go into detail in your responses

Another day,
-vhelp 2030