Using AE for 29.97fps to 24fps conversion

[Steve Mullen]

Working on my review of Aspect HD I decided to try AE.

No problem Importing CFHD material or Exporting using CFHD.

So, just for fun, I decided to do an export to 24.00fps. It had a funny jerky look.

So I turned on Frame Blending and the result looked very good.

Others should experiment with AE and see if this solution works.

Of course, you can use AE on both PC and Mac to convert exported uncompressed HD movies.

This could be very good news -- or an error on my part.

[Alex Raskin]

Re:Vision's TWIXTOR plug-in for AE does frame rate conversions professionally, among other things.

[Ken Hodson]

Magic Bullet will also perform the said funtion. Although it is generally recommended to go from 60i to 24p. Unless your final product is for film it is not recommended to use 24p. 30p looks much nicer. Even panasonic DX100 users find that 30p is much nicer then the 24p on their cameras.
Now a question. I understand that this camera can upsample to 1080i on playback. Can this output be taped using a DVHS, then transfered back to PC then converted to 24p?
Ken

[Barry Green]

As a DVX user, I shoot almost exclusively in 24P, I only use 30P for slow-motion effects, and many agree. Shooting in 30P not only precludes the possibility of a film transfer (which is a very remote possibility) but also prevents getting a quality PAL transfer, which is (or should be) an important consideration. 24P makes for extremely nice PAL transfers, with a speed adjustment to the audio.

[Steve Mullen]

1) I can't think of any reason would convert to 24 except for film.

2) The point is that everyone -- including me -- says you can't shoot 30p for film. But, other my test i haven't seen any confirmation of this belief. Maybe it's time to experiment.

3) And I didn't see a problem with the output. Most of us have AE so it makes sense to try it rather than paying for a plug-in.

4) D-VHS can only record analog SD. Head to www.videosystems.com for my review of the new D-VHS deck.

[Alex Raskin]

AE is OK only as a low-quality, lower-cost solution, because AE only discards frames/fields and then duplicates/combines the others to produce new frame rate.

Twixtor, on contrast, actually *creates new frames* out of thin air as needed.

Results are spectacular. I was able to use Twixtor on 29.97 DV footage of a prop gun shot, to slow it down 10x - you should see the gorgeous gun smoke in quality slo-mo as if shot by way overcranked camera!

Re:Vision has some info/illustrations on their site, plus do search DV.com for the article of, I believe, Rev. John Jackman reviewing slo-mo techniques. Twixtor is hands down the best.

[Barry Green]

<<<-- Originally posted by Steve Mullen :

2) The point is that everyone -- including me -- says you can't shoot 30p for film. But, other my test i haven't seen any confirmation of this belief. Maybe it's time to experiment.
-->>>

I saw a Canon XL1 "frame mode" short film transferred to 35mm, and it was unwatchable. The motion artifacts were jarring and disturbing. And film transfer houses I've talked to have said the same thing -- 30P is the worst possible choice.

Now, technology marches on, and who knows -- maybe someone has invented a usable technology for converting 30P to 24P since we last checked. I don't know of any, but maybe there is something out there...

[Steve Mullen]

<<<-- Originally posted by Barry Green : saw a Canon XL1 "frame mode" short film transferred to 35mm, and it was unwatchable. The motion artifacts were jarring and disturbing. And film transfer houses I've talked to have said the same thing -- 30P is the worst possible choice.
-->>>

Relax, I'm only letting folks know they could try this.

And one transfer does not mean anything.

Perhaps the transfer technology depended on interlace as does SE.

[Maheel Perera]

As far as I know, transfer companies do not convert 25p to 24 when transfering to film. Normaly it is transfered as it is and the sound track is stretched a bit to compensate for the extended time. Witch is 1 frame for every second.

So it is best to try experimenting on 30p to 25p instead of 30 to 24. The computation is much simpler.

It is not practical to convert an entire movie (at least 90 minutes ) using Twixtor. Although Twixtor is great for shorter length shots it will take ages to convert a feature length film to 24p with the required correction masks etc.

[Ken Hodson]

If you are in the less than 1% that will ever need to transfer to film, I am sure you can tollerate the render times with Twixtor. After all the movie must be money in the bank to even want to bother.
Ken

[Steve Mullen]

1) So you are suggesting 29.97 to 25.00 as simpler to compute than 29.97 to 24.00? Or, 29.97 to 25/1001? And, HOW to arrive at the simpler?

2) Actually, in OUR group I agree the percent going to film is very small.

But my 4HDV is selling to a whole other group that are shooting movies. So they do need to consider the conversion and one hopes are budgeting both time and money.

[Maheel Perera]

I used AE for the tests. It confirmed your observations. How ever I have noticed

1. It takes less time to render 30fps to 25fps than 30fps to 24fps.

2.The resultant footage with frame blending showed a ghosting like effect on the fast moving areas of the frame.

There is another method I am working on. I may be in a position to discuss the results in about a month. I am planning to transfer some footage to film and see.

[Steve Mullen]

<<<-- Originally posted by Maheel Perera
2.The resultant footage with frame blending showed a ghosting like effect on the fast moving areas of the frame. -->>>

You are right. I saw the same thing. It reminded me of the old days of PAL to NTSC conversion done by the BBC.

I wish you luck in your experiments. I don't know enough about AE's Frame Blending to go further. I was just happy to see smooth motion!

[Robert Knecht Schmidt]

Twixtor's vector computation is highly utile, but it isn't magic, particularly for fog, smoke, and clouds, where foreground motion may be quite large from frame to frame and edge details are nebulous and shifting.

A project I'm working on now called for a sky replacement. An HD res sky with motion from a library was beyond the producer's budget for the shot, so I took my little Canon S110 down to the lake on a beautifully cloudy day and got 138 frames of an almost-HD-res time-elapse sky on a single 128 MB CF card, which I then retimed with Twixtor to slow and expand to the full time of the project (649 frames). While the distant clouds are smoothly frame-interpolated, foreground clouds jerk and pulsate--and this with all of Twixtor's various quality settings on 'best.'

I understand RealViZ Retimer allows for manual editing of the motion vectors, which would probably help cut down this sort of retiming artifacting. (Retimer is quite often used for retiming smoke effects. They have a neat little Quicktime on their web site showing it in action for smoke and particles on the film Enemy at the Gates.)