Lowering AVI frame rate causes jerky movement

[bvdd]

Hi all,

I searched for this but found nothing specific.

I'm transferring 8mm films to my hard drive. I run them with a projector and film them with a Sony Digital 8 camera.

To eliminate the 'Flickering' I speed up the projector, film the movie with camera, then transfer to my PC via Firewire using WINDV.
That gives me a good visual movie - but it's clearly too fast.

So now I'm trying to lower the frame rate of the AVI from 30fps to 18 or 16fps which is closer to film. That produces a jerky result and
even when I try lowering to just 24fps it's not smooth.

My question: Is there a particular software program known to do a really good job at this, or is it just the nature of the beast and
I'll get the same result no matter what I try?

I'll gladly buy a new program if it does the job.

So far I've only tried two freebees - Virtual Dub and AVIFrate.

Thanks,
Bill

[jagabo]

You have to inverse telecine back to the (sped up) film frame rate then lower the frame rate to 16 or 18 fps. And those low frame rates are inherently jerky so you will still have jerky flickery video.

You'll probably have to use AviSynth for this. If you upload a sample with motion someone will give you a sample script.

[manono]

So now I'm trying to lower the frame rate of the AVI from 30fps to 18 or 16fps which is closer to film. That produces a jerky result and
even when I try lowering to just 24fps it's not smooth.

Perhaps you're lowering the framerate by removing frames? That will certainly account for the jerkiness. If the film length is the same after as before, then that's what you're doing. What you want is to slow the video so it's length is greater than originally. You haven't said how you're accomplishing this framerate change but, as jagabo said, a sample will help to figure out what's going on. Not much, just ten seconds or so with steady movement. And as he also says, AviSynth is the way to go to accomplish what you want - both remove any duplicate frames and also slow the video.

[bvdd]

Thanks for the replies,

The processed clip is definitely longer time-wise so I don't think I'm removing frames.

Should the clip I upload be from the original file with no frame rate change - or after the change?

I've been using Virtual Dub so far.

Thanks

[jagabo]

Upload the original file. Or both.

[bvdd]

Ok, I have a clip.

I have Dropbox - upload there or somewhere else?

[Bjs]

When speeding up source you need to also increase the speed of the recording device

Its a bit like every second frame not being captured and slowing the capture file down will result in jerkiness no matter what you do.

Using blend mode in avisynth will cause visible, although slight, blurring of motion

This post should cover what your looking for in avisynth

[bvdd]

That link just made me realize how out of my league you guys are with this stuff.

May be time to accept my movies looking like the Keystone Cops - or can this project.

Thanks so much for your help everyone.

[manono]

Bjs brought up a good point - that perhaps the jerkiness/frame dropping occurred during the transfer. That to increase the framerate it wasn't speeded up but frames removed. Anyway, a sample should tell the tale.

You can upload here, or to a file sharing site such as MediaFire or SendSpace. I suppose Dropbox is okay if we don't have to jump through hoops (by signing up, for example) to get at the file.

[jagabo]

Yes, you can upload files up to 500 MB here. Note the "Upload files/Manage attachements" button below the "Quick Reply" edit box below.

[Speed Daemon]

I'm transferring 8mm films to my hard drive. I run them with a projector and film them with a Sony Digital 8 camera.

To eliminate the 'Flickering' I speed up the projector, film the movie with camera, then transfer to my PC via Firewire using WINDV.
That gives me a good visual movie - but it's clearly too fast.

So now I'm trying to lower the frame rate of the AVI from 30fps to 18 or 16fps which is closer to film. That produces a jerky result and
even when I try lowering to just 24fps it's not smooth.

My question: Is there a particular software program known to do a really good job at this, or is it just the nature of the beast and
I'll get the same result no matter what I try?

A few points:

1. You made a good decision to sync your film frame rate to your video frame rate. That keeps every original frame that you have. When you're starting at 16-18 fps, it helps to keep and use all the image information available to you.

2. You're using an interlaced video format as the intermediate between film and computer. That can work, but you need to be mindful of field alignment and deinterlace methods to make those frames whole on your computer. You should choose "weave" deinterlace to restore the frame. If you can't control that at ingest, you may have more problems than you need going forward. Using a progressive scan camera for ingest can eliminate all interlace problems.

3. Since you're shooting video at 30fps (actually 29.97 frames/sec.) with an overcranked projector, your digital video metadata is the only thing that's wrong. If you can fix the metadata without changing the number of frames you're set. What I think might be happening here is that your software is reducing the number of frames total to give you the desired number of frames per second--that defeats the purpose of keeping all of those frames intact!

4. If you use a metadata editor to edit the metadata but not the video, so that it says "this is 18fps" (right now it probably says "this is 30fps"), when you play back the corrected video file, it may still look a little funny, but that's because you started with a very low frame rate. Once you're sure that you have saved every frame, you can then use post production effects like motion blur to make it look pretty on a 60Hz (assuming you're in the US) computer monitor.

I'm not a big AVI user, but found "abcAVI Tag Editor" in a Google search. There are more tools for MPEG video, of course.

[bvdd]

Ok, here's a short clip. No processing has been done.

[manono]

I'm not positive this is what's going on, but it looks to me that someone assumed it was 20fps (19.98fps) and then 'telecined' it to 29.97fps. I removed the dupes (most anyway) to get it back to 19.98fps and then slowed it to 17.982fps. It still looks a bit speeded up to me, so maybe it's supposed to really be around 16fps. To do that it's a simple matter of changing the AssumeFPS command in the script.

AVISource("SHORT TEST.avi")
QTGMC(Preset="faster")
Srestore(Frate=19.98)
AssumeFPS(17.982)
Crop(8,0,-8,0)
LanczosResize(640,480)

[jagabo]

I agree with manono. You sped the projector up to 19.98 fps and recorded at 29.97 fps interlaced. So each film frame appears for three consecutive fields. Some of the fields are blends of two film frames (because the projector switched frames while that field was being captured) so you want to preferentially remove those, along with other duplicates, with SRestore(). Then you just AssumeFPS() to the frame rate you want for the final output.

If you are going to DVD or Blu-ray, or some other format which requires specific frame rates you'll need additional handling.

[bvdd]

That's a much better result than I got.

That movie was shot around 1959 so I would say it's definitely 16fps.

You did this with AVISynth? Is there a tutorial on it for a newbee?

[bvdd]

I'm watching a quick tutorial now.

[LMotlow]

AVISource("SHORT TEST.avi")
QTGMC(Preset="faster")
Srestore(Frate=19.98)
AssumeFPS(17.982)
Crop(8,0,-8,0)
LanczosResize(640,480)

I figured you're the type who likes fat girls and oval-shaped tires, but maybe the owner doesn't want the image distorted. I'm really surprised by that amateur resize. Shame on you.

[jagabo]

I'm really surprised by that amateur resize. Shame on you.

You're the amateur here. It's DV. The resize is appropriate for that. If there's an AR problem it's in the film or projector.

[manono]

I figured you're the type who likes fat girls and oval-shaped tires, but maybe the owner doesn't want the image distorted. I'm really surprised by that amateur resize. Shame on you.

What? And how would you handle the crop and resize? Are you saying 720 should be resized to 640 (if using square pixels) and not 704? It, admittedly, doesn't have any real black bars on the sides, but it does have darkened sides which I thought better to crop away. At most, you're quibbling over a 2.5% aspect error, hardly enough to notice, hardly enough to create fat girls and oval-shaped tires, and hardly enough to pick a fight over. There are more polite ways to disagree with someone.

I generally use ITU resizing. Maybe that's because I work with so many tape sources captured as DV-AVI. If it's not supposed to use ITU, then bvdd can do it any way he likes and thanks for pointing out a possible mistake.

[Speed Daemon]

It looks like pulldown to me. A 3:2 pulldown works for 24fps movies only. It should not be used for other film frame rates.

If you have a variable rate projector, perhaps slowing it down to 15 fps (actually 15 * 1000 / 1001) will yield the best results. NTSC video has a 4-field color frame, so shooting at ~15fps makes sense. The problem is still in 1.) avoiding any pulldown algorithms, 2.) specifying a weave interlace during the NTSC to AVI file conversion. You want the video file to have full 720x480 progressive scan frames. I don't know if WinDV can do that. This may require another IEEE-1394 ingest program.

[jagabo]

You want the video file to have full 720x480 progressive scan frames.

About the only way to get that is with a film scanner or a DSLR with an externally controlled shutter (and a modified projector). That will also give better overall results but will cost big bucks.

[manono]

You did this with AVISynth?

Yes, that's an AviSynth script fed into RipBot264 for the encode. Tutorial? Not really, except for suggesting you read in the AviSynth website. In addition there are lots of instructions given here to others just starting out, ones such as PuzZLeR's here:

[manono]

A 3:2 pulldown works for 24fps movies only. It should not be used for other film frame rates.

So how have the hundreds of silent films released on DVD managed to be hard telecined from base framerates other (usually lower) than 24fps? Of course, it's not 3:2 pulldown but it's perfectly okay to use it.

If you're referring specifically to film scanners (you didn't say in that first line), it seems to have done an okay job to me.

Your location? Did you make up a new word? Is it supposed to mean 'wanderer'? If so, shouldn't it be spelled as 'itinerant'?

[Speed Daemon]

About the only way to get that is with a film scanner or a DSLR with an externally controlled shutter (and a modified projector). That will also give better overall results but will cost big bucks.

It should work fine with the existing film chain. Here's how it works:

The film flashes ~15 times a second. The video camera records a new field every 1/60th of a second or 60 frames/sec, with each 2 frames making a whole frame. Because the two successive fields are of the same, a simple weave algorithm can combine the two NTSC fields into a solid 720x480 frame in the digital domain. The only crucial thing is to maintain sync between the projector and camera. That will take some skill and patience, but in the long run it's easier than trying to create a pulldown for 15fps to NTSC and then to digital.

Once it's in the digital format, processing is easy, given the right tools. At 15fps for the film, the video camera will probably see darkness as the projector's shutter closes. Using something like SelectEvery() in AVIsynth will remove the dark frames and restore the actual frame rate to ~15fps. It probably can be shown as-is from there. You could overcrank that to make up for the 16fps/15fps differential if need be.

[jagabo]

The only crucial thing is to maintain sync between the projector and camera.

And that's not possible with a simple projector camcorder setup.

Even if you get "good enough" sync for short periods, it's still pulldown -- 4:4.

[Speed Daemon]

And that's not possible with a simple projector camcorder setup.

Even if you get "good enough" sync for short periods, it's still pulldown -- 4:4.

No, there's no pulldown. It's a standard projector. No matter what you want to call it, trying to apply a reverse telecine digital filter on the NTSC video will only make things worse.

How long is a typical 8mm home movie? A few minutes? I think that might be a short enough sample for someone to at least try to ride sync and see how far that gets him/her. It's not a permanent solution for a production environment, of course. But what's the alternative? Shoot it as-is? Pay to have it scanned?

[bvdd]

I'm not positive this is what's going on, but it looks to me that someone assumed it was 20fps (19.98fps) and then 'telecined' it to 29.97fps. I removed the dupes (most anyway) to get it back to 19.98fps and then slowed it to 17.982fps. It still looks a bit speeded up to me, so maybe it's supposed to really be around 16fps. To do that it's a simple matter of changing the AssumeFPS command in the script.

AVISource("SHORT TEST.avi")
QTGMC(Preset="faster")
Srestore(Frate=19.98)
AssumeFPS(17.982)
Crop(8,0,-8,0)
LanczosResize(640,480)

What application are you using to do this? I tried to recreate what you did using VirtualDubMod but I got this message:

"Script Error - There is no function named "QTGMC".

[jagabo]

QTGMC() is not built into AviSynth. It's a third party filter (script). It also requires several other third party filters that you will need to download and install.

http://avisynth.nl/index.php/QTGMC#Requirements

[jagabo]

And that's not possible with a simple projector camcorder setup.

Even if you get "good enough" sync for short periods, it's still pulldown -- 4:4.

No, there's no pulldown.

Of course there is. Pulldown is the process of producing 60 fields per second from a lower frame rate. You're simply relying on the sync between the 15 fps projector and 30i camcorder to pair fields from the same film frame together into video frames.

[Speed Daemon]

Pulldown is the process of producing 60 fields per second from a lower frame rate.

Well that's the Underpants Gnomes version at least. Old farts like me who were around to see the last film chains in use have a somewhat more complete definition. But if you want to use that word as synonymous to frame rate conversion, fine by me.

You're simply relying on the sync between the 15 fps projector and 30i camcorder to pair fields from the same film frame together into video frames.

Yep. The beauty of that is that it actually works. There are no temporal differences coming from that same 8mm film frame, so the fields interlace perfectly. No motion judder or other artifacts that come from asynchronous methods. Interlace is normally the source of all sorts of temporal errors; this makes it a non-issue. So far I don't see any better suggestions that work with what the OP has.