Best way to achieve smooth slow motion?

[nzo]

I have some S-VHS video footage of sea birds filmed at regular speed, which I'd like to slow down and put to a sound track.

Of the various editors, are some better than others at achieving smoothness?

Maybe there are plug-ins that help with slo-mo?

Sure would appreciate some help with this.

Thanks ~ John

[doppletwo]

Sorry

In the DVD commentary for Once upon a Time in Mexico and Desprado Robert Rodriguiz says that you have to shoot it at a higher frame rate.

Like if you want to slow it don't to half speed shoot film at 48 fps instead of 24 fps.

video is 30 fps or 60 half frames per second.

I don't think you can achieve good slow mo after the fact. You are missing frames

Maybe I am wrong though. there could be some sort of software that could interpolate the intermediate frames that you are missing.

But that kind of stuff would probably be quite expensive.

[mpack]

As Doppletwo says, the best (and only) way to achieve truly smooth slow motion is to capture at a high frame rate and then play back at the normal frame rate.

Frame interpolation is surprisingly tricky. It is not just frame averaging as you might imagine, as that would result in a dissolve, not a 'tween frame. What you have to do is similar to the motion compensation step in MPEG... for every point on the latest frame you have to find the best match for the corresponding point on the previous frame. That gives a motion vector for that pixel, which is what you interpolate in order to generate the 'tween frames.

[dphirschler]

You can get pretty good results if you do a bob deinterlace. That will give you double the frames. Then you can try creating twean frames by combining every frame with the frame before it. So it would be like this:

start with 30 fps interlaced
bob converted to 60fps progressive
slow down to 30 fps progressive
create intermediate frames

result:
frame1, frame1/2, frame2, frame 2/3, ect.


Darryl

[dphirschler]

Here are two methods of doing it in AVIsynth. There may be easier ways, but I did it this way. Slowmo_1 is half speed. Slowmo_2 is one third speed.

v= AVIsource("test.avi") # source is 30 fps interlaced at 720x480

#return slowmo_1(v)
return slowmo_2(v)

function slowmo_1(v)
{
	v= assumeTFF(v)
	v= bob(v)

	return v.assumefps(29.970)
}

function slowmo_2(v)
{
	vi=v
	v= assumeTFF(v)
	v= bob(v)
	v0= selectevery(v,2, 0)
	v1= selectevery(v,2, 1)
	n= interleave(v0,vi,v1)

	return n.assumefps(29.970)
}

[dphirschler]

Here is another one. This one is for slowing to 1/4 speed. You sacrifice a little clarity for smoothness due to blending, but it's not so bad.

function slowmo_3(v)
{
	v= assumeTFF(v)
	v= bob(v)
	v= interleave(v,v)
	v0= selectevery(v,2, 0)
	v1= selectevery(v,2, 1)
	v1= deleteframe(v1,0)
	vc= overlay(v0,v1, mode="blend", opacity=0.50)
	n= interleave(v0,vc)

	return n.assumefps(29.970)
}

Darryl

[doppletwo]

There is another slow motion thread that talks about software called Twixtor.

I am not familar with this at all.

you might want to check out the other thread. But the guy Cactus seems to no understand the concept of slow motion.

Everybody trying to help makes sense though.

[Deekkeed]

I have had very good results using Sony Vegas 5 for ¼ speed of my kids jumping on a trampoline.

[guns1inger]

Vegas' velocity envelopes are very good, and have a little more freedom than a simple slow motion effect.

Twixtor is a brilliant plugin/standalone app for altering speed. It uses a mixture of morphing tecniques and motion vector analysis to produce high quality results. It is the next best thing to shooting it properly in the first place.

[daamon]

I've done half-speed (50%) in Adobe Premiere v6.0 and it looked perfectly OK.

[mpack]

You can get pretty good results if you do a bob deinterlace.

That's really just describing a method of frame averaging. You get a slow dissolve that way, you don't get slow motion.

To illustrate, lets say you have a sports broadcast involving a ball in motion. On one original frame the ball is in position A. On the next frame the ball is in position B.

With frame averaging you will never see the ball in an intermediate position C, all you will see on the interpolated frame is blurry versions of the ball at both positions. To see the ball in position C there is no alternative to motion estimation.

[dphirschler]

I stand by what I said. However, I will qualify my statement by limiting it to interlaced video. Bobbing effectively creates two moments in time for every frame. It works because interlaced video is really ~60 fields per second. So you convert the fields to frames and now you have double the frames.


Darryl

[mpack]

I stand by what I said.

Oh - ok, I see what you mean. That's a very limited form of slow playback though (I won't call it slow motion, since it can't cope with motion). By expanding each field to frame height then playing back the fields at the frame frame rate you are in effect just asking the TV to display each field twice (to all intents and purposes the same as the original field). Repeating fields or frames is how a DVD player works its slow picture search trick, and for all I know that might be all thats needed in this application.

[junkmalle]

One technique I've used on occasion is to first duplicate frames. This of course just ends up showing the same picture several frames in a row, then flipping to the next picture, etc. But then I add a big temporal filter. This creates a cross fade around the frame changes.

The final result is a still image of frame 1 for a while, a crossfade to the frame 2, a still picture of frame 2 for a while, then a crossfade to frame 3, etc.

[mpack]

But then I add a big temporal filter.

See my earlier message: you are again describing a dissolve (or crossfade as you put it), which is quite different from slow motion.

[junkmalle]

But then I add a big temporal filter.

See my earlier message: you are again describing a dissolve (or crossfade as you put it), which is quite different from slow motion.

I'm fully aware it's not true slow motion. But sometimes you have to work with what you have.

[housepig]

there's another software out there, Realviz Retimer, which will attempt to create missing in-between frames.

it's been a while since I played with it, it seemed to do a pretty good job.

[mpack]

I'm fully aware it's not true slow motion.

It isn't just that it's "not true slow motion", it isn't motion at all, in any sense. It's just a dissolve. If an object appears at position A on one frame and at position B on a later frame (A != B) then no amount of crossfading will let you see the object at any position other than A or B (in fact it will appear in both positions on the interpolated frames).

Slow motion allows you to see motion: in other words the object should appear at intermediate positions on intermediate frames. Simulated slow motion requires a morph, not a fade.

[Richard_G]

I don't know how it does it or if it is what is required but I use Ulead Mediastudio Pro (version 6.5). I can place an avi clip on the timeline, right click on it, select speed and set it at any percentage speed between 10% and 1000%. Setting it at 50% gives me half speed and so on. The result is smooth slow motion.

A 30 day free trial of MSP can be downloaded from the Ulead site, might be worth trying it and seeing if it does what is wanted. Slow down the clip and then save it as a further avi file but at a different speed.

[junkmalle]

Ulead Media Studio Pro simply repeats frames when you slow video down. Slow it down to 10 percent for example and you'll see that each frame is displayed 10 times.