DVX100 30p to 24p samples

C

ClaytonF

Active member
In response to a request in another thread here are some brief clips (at full DV res) of taking a 30p clip and slowing it down for use in a 24p edit (becomes 80% speed of original.)

http://homepage.mac.com/dvx100_tests/index.html

FWIW here's what I stumbled along testing this out:

* By far the easiest way to do this is to use Cinema Tools (comes with FCP4) to 'conform' the 29.97 clip to 23.98. This is instantaneous. It does directly alter the original clip so you would probably want to work on a renamed copy.

* For those without FCP4 or Cinema Tools, you can also do this in Quicktime, although it is a bit more tedious. There might be a more efficient method/workflow (or create an applescript action?) but basically you can save the original clip out as an image sequence and then reopen the sequence at the new (23.98) timebase. This can then be saved out in either an uncompressed or DV codec (although in my limited tests there was no perceptible difference in this one DV codec pass.)

* There is also a program called MediaPipe which was one of the few utilities I could find that would alter the frame rate of a QT movie file. It is available here: 'http://mediapipe.sourceforge.net/MediaPipe'. It did work, and actually rather fast, but produced a result slightly shifted in time from the QT approach above. This was only noticeable when stepping through a frame at a time and probably wouldn't be an issue otherwise. If you don't have access to Cinema Tools this might be an efficient solution. (If of interest I can post more specific details to the settings I used here.)

The processed clip above was done using Cinema Tools.

I don't know how long Apple will host these examples on their trial account, but they're ripe for the picking until then.

Hope this helps,
Clayton
 
Re: DVX100 30p to 24p samples

Hi Clayton,
Thanks so much for taking the time to go through all this. You're god like in your kindness.

That being said, however, after looking at the before and after effects of what you did... well there really isn't a noticable difference in terms of slow motion (which is originally what I was asking about). If anything, what you acheived is more like a 3:2 pulldown effect changing 30i footage to read like 24p footage visually.

For my purposes, I'm looking to do something that reads like slow motion as used in action films (think John woo). Well not really John Woo, but that's the best way I can think of to explain the visual effect I have in mind.

Suggestions?   ???
 
Re: DVX100 30p to 24p samples

[quote author=STORYTELLER32 link=board=Clips;num=1068237783;start=0#1 date=11/08/03 at 05:39:13]Thanks so much for taking the time to go through all this...after looking at the before and after effects of what you did... well there really isn't a noticable difference in terms of slow motion[/quote]

You're welcome. As for the speed difference, bear in mind that it is only a 20% reduction in speed. What is nice about it though is that is using real frames as opposed to ones that have been interpolated. Also, this was about as long of a clip as I could post on that server. I tried to grab something with some fast motion (albeit dark), but doing the same thing on a longer/different clip might be more revealing.

If anything, what you acheived is more like a 3:2 pulldown effect changing 30i footage to read like 24p footage visually.
Click to expand...

Just to clarify it is still all progressive - going from 30p to 24p (not 30i [or rather 60i - 60 fields].) Also, whereas pulldown retains the same overall length of the footage in time this is actually slowing things down (but as mentioned, not by very much.) This is where it would be good to be able to view the effect on a longer clip. You may find it is most useful for subtly 'smoothing' out mos shots.

For my purposes, I'm looking to do something that reads like slow motion as used in action films (think John woo). Well not really John Woo, but that's the best way I can think of to explain the visual effect I have in mind.
Click to expand...

This is where you'll need to fake a higher frame rate. Like overcranking a film camera. I think it may have been mentioned before, but another relatively 'free' way would be to shoot at 60i, then separate the fields and interpolate each of them back into a full frame. This would obviously have a lower vertical resolution than the true progressive stuff from the camera, but would give you a significantly slower effect and may look better than simply doing frame blending in Final Cut Pro or the like. Then there is the previously mentioned option of a program like Twixtor (www.revisionfx.com), which although making up fake 'tween frames is doing it pretty intelligently instead of just cross blending.

Here comes that testing thing again...

Hope this helps,
Clayton
 
Re: DVX100 30p to 24p samples

Gotta love Clayton. His responses are always clear and well thought out.  ;D
You're absolutely right that going the Twixtor route is best as opposed to the 60i separation. I'll have to look at my budget when the post work comes around. Maybe I'll just shoot the scene twice but at different frame rates to cover myself in post. :) Got the shoot coming up next weekend so wish me luck!

Still looking forward to more testing on your part though. You go boy!
Storyteller32
 
Re: DVX100 30p to 24p samples

There was no sarcasm in the gotta love clayton thing. I meant it! ;D
storyteller32
 
Re: DVX100 30p to 24p samples

Anybody that knows a good way of separating fields (50i/60i to 50p/60P) for slow motion effect?
 
Re: DVX100 30p to 24p samples

I've heard of people taking 60i footage and coverting it to 24p thereby achieving 40% of the standard speed. Anyone have any ideas on how to achieve that easily using FCP and Cinema Tools?

I think the process goes something like this:

1. Capture at 60i.
2. Take each field and interpolate it or double it. (You're missing a field with each 60i image and have to create the missing odd or even field.)
3. Then, use that field to create a new frame.
4. Then, take the 60p frames and play them back at 24fps.

Thoughts?

Russell
 
Re: DVX100 30p to 24p samples

i was wonderingthe same thing. Also to shoot in thin mode to make up for the res loss

jesse
 
Re: DVX100 30p to 24p samples

[quote author=ponder8n link=board=Clips;num=1068237783;start=0#7 date=11/10/03 at 11:13:45]I've heard of people taking 60i footage and coverting it to 24p thereby achieving 40% of the standard speed.  Anyone have any ideas on how to achieve that easily using FCP and Cinema Tools?

I think the process goes something like this:

1.  Capture at 60i.
2.  Take each field and interpolate it or double it.  (You're missing a field with each 60i image and have to create the missing odd or even field.)
3.  Then, use that field to create a new frame.  
4.  Then, take the 60p frames and play them back at 24fps.

Thoughts?

Russell
[/quote]

That's explained here. http://www.100fps.com

They even have sample clips and the footage is amazing.
 
Re: DVX100 30p to 24p samples

good site with a lot of good info but the slow mo seems to be with program similar to twixtor. Not really anything about extracting each fild as frames. Unless i missed it.

jesse
 
Re: DVX100 30p to 24p samples

Hmm, looks like you're right, but the site does show how to create 50fps videos with 50i footage. I was thinking if you could just slow the framerate down to 25 while keeping all 50 frames, you can achieve the true slomo at 50%.

Actually, I'll try this out right now. I wish I could post results, but I don't have much webspace.
 
Re: DVX100 30p to 24p samples

Hey I did it! It's not that hard and the results look great.

First, output a 50fps or 60fps video with some 50i or 60i footage following the tutorial on http://www.100fps.com

Then open the file with virtual dub. Go to Video --> Frame Rate and select change to _____ fps. Type in your desired framerate you wish to slow down the footage. Assuming your source footage was ntsc (60i), choosing 23.98 would slow down the footage to 40% as ponder mentioned. Then output your video to the format of your choice. What's great about this method is that it's completely free!

I'm going to slow it down even further using Twixor now. If anyone has any questions, feel free to ask.
 
Re: DVX100 30p to 24p samples

Sorry this is my last post I promise. This soccer clip from www.100fps.com was aired in slow motion. The guy used dynapel (slomo program) to create extra frames inbetween to make a pseudo-slow motion effect. It looks really good (some artifacts though). What I found out was that he didn't even touch the framerate. It was still left at 50fps. So I decided to set the fps to 24 and instantly I got the footage twice as slow.

So since it was aired in slomo, it was already 3 about times as slow. The site owner used dynapel to make it 3 times slower than that to make it about 9 times slower. After I brought the framerate down to 24, this made the footage 18 times slower! That's 5.55555555 percent of the original play, and 16.6666667 percent slower than the source footage. Another note, this is PAL which means with NTSC, the footage can be even slower (due to more frames). I've never seen DV footage this slow and smooth before. It's almost surreal.

Tomorrow I'm going to test some more, right now I need to get some sleep.
 
Re: DVX100 30p to 24p samples

well i have a trick i used a couple of years ago. I Just told the actor to move real slow (If he/she is a good actor) they can make it real good so long as you dont have to break the laws physics, like gravity or water etc. Then you can use your standard postproduction technice to slow it down even further.
 
Re: DVX100 30p to 24p samples

Hey,

While out of town I did my best to take a vacation from my internet habits as well (highly recommended...) so I've just seen that I suggested the 60i thing and didn't follow-up with how to do it.

It's been a while since I've had to try and do this myself, but I think that either After Effects or Commotion are up to the task. As for a less expensive / free solution it sounds like VirtualDub works for the PC or you can try this for the Mac:

http://www.macupdate.com/info.php/id/13069

or here

http://home.planet.nl/~jeschot/#DEI

I haven't played around with it too much, but it seems to do what it advertises. The interface and documentation are a bit awkward, but basically set up a 'deinterlace' project, select "both fields" & "double movie duration", deselect "top line in earlier field" (I'm guessing this means it is upper field dominant, which wouldn't be the case with DV footage) and output with the DV-NTSC compressor.

The results are fairly nice although artifacts start becoming pretty evident in areas with straight lines that are not moving (backgrounds, etc.) What would be nice is a way to mask out only the motion / interlaced portions of the picture for interpolation when splitting the fields. (Similar to the masks that utilities like DV Film, FieldsKit, and GFilm use.)

Speaking of GFilm, it is probably also worth checking out Graeme Nattress' Final Cut Pro plug-in for this very thing as soon as it is ready. (At http://www.nattress.com - part of his "Set 2" of plug-ins.) With any luck it will be capable of having more control over these kids of problems.

Once you've done this you should have a half speed clip (2x the running time) at 29.97fps. You could then bring this to 23.98fps via the techniques above for ann additional speed change.

Hope this helps,
Clayton
 
Re: DVX100 30p to 24p samples

Excuse my ignorance, but to clear things up. If you import a 30p clip into a 24p timeline, does it need to go through a pull-down of it's own, or does it simply spread it's 30 frames across 30 frames of the timeline. Is it like importing a 24p (normal) clip, where it needs to be recompressed?

Basically I'm asking if the 20% slow-down method using 30p causes any loss in quality at all. I suspect the answer is no, but obviously I'm still a bit confused.

I think that mixing 24p advanced footage and 30p is without problem. Mixing 24p normal and 24p advanced would mean that one of them would have to conform to the other. Please help me out. Thanks!
 
Re: DVX100 30p to 24p samples

Clayton, I have a question to.

>> You're welcome. As for the speed difference, bear in mind that it is only a 20% reduction in speed. What is nice about it though is that is using real frames as opposed to ones that have been interpolated. Also, this was about as long of a clip as I could post on that server. I tried to grab something with some fast motion (albeit dark), but doing the same thing on a longer/different clip might be more revealing.<<

So does a longer clip look just like 24p, or does it look like slow motion, of some sort? Just want to be clear on this.
 
Re: DVX100 30p to 24p samples

[quote author=Zot link=board=Clips;num=1068237783;start=0#16 date=11/24/03 at 10:10:51]Excuse my ignorance, but to clear things up. If you import a 30p clip into a 24p timeline, does it need to go through a pull-down of it's own, or does it simply spread it's 30 frames across 30 frames of the timeline. Is it like importing a 24p (normal) clip, where it needs to be recompressed?[/quote]

Hi Zot - I am not in front of Final Cut right now but I bet if you toss a 30p (29.97fps) clip into a 24p (23.98fps) timeline that it will not perform this slow-down as you'd expect. It will probably drop intermittent frames to play in 'real-time'. (Which would make for jerky playback.) Just half-remembering / guessing though - the best thing to do would be to try it and see what you get. But in any case, yes it will need to be rendered since the timebase of the clip and timeline are different.

Basically I'm asking if the 20% slow-down method using 30p causes any loss in quality at all. I suspect the answer is no, but obviously I'm still a bit confused.
Click to expand...

Using the approach of going to 24p from 30p mentioned above with something like Cinema Tools loses no quality as it is not rerendering the clip, just adjusting its timebase.

I think that mixing 24p advanced footage and 30p is without problem. Mixing 24p normal and 24p advanced would mean that one of them would have to conform to the other. Please help me out. Thanks!
Click to expand...

If you are using 24pn and 24pa together, then the common ground to bring them together for editing would of course be 24 fps (23.98). So it's just a matter of removing the pulldown from each of them first. In FCP4 you can remove the advanced pulldown either during capture or after the fact in FCP. With normal pulldown, you will use Cinema Tools to remove the pulldown before editing. At that point all of the clips should be 23.98 fps and can be cut together normally.

(If you are looking to just edit at 29.97fps, then you would have some issues with cutting 24pn and 24pa together since the 24pa pulldown cadence would probably still out as being odd.)

[quote author=Glenn_Gipson link=board=Clips;num=1068237783;start=0#17 date=11/24/03 at 11:46:38]So does a longer clip look just like 24p, or does it look like slow motion, of some sort? Just want to be clear on this.[/quote]

The length of the clip doesn't have anything to do with the effect, I was just commenting that you would probably be able to detect the speed difference in a clip that was longer or had different motion in it. As for looking "like 24p", it will be playing back at 23.98fps but will just look like the camera was overcranked - like running a film camera at a higher frame rate when shooting and then projecting back at 24fps. So you are using all real frames but have more frames per second than real-time (the playback fps). In this case it will be a 20% slow-down.

Hope this helps,
Clayton
 
Re: DVX100 30p to 24p samples

Thanks Clayton! I think I finally got it.

The fact that the camera can undercrank without any degradation of image (although only 20%) is a woefully underadvertised bonus! I think this look could definately add some nice texture to scenes with a lot of movement like dancing or sports or something. I appreciate your help and I will start to experiment. I just got my camera.
 
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