- [Instructor] The retime node can speed up
or slow down clips and even offers a variable
speed time warp capability.
However, it's a simple node that only offers
simple frame interpolation methods.
So let's take a look.
I'll select the read node, come up to the time
popup and select the retime node.
I'll home the viewer, make it a little larger.
What we have here is simply a numbered clip
that tells us exactly what frame we're on
so we can see the action better.
Starting up here on the retime property panel
there's two ways to set your speed.
First of all, we could set a speed value.
Let's say I want this to go at 20%.
So I'll enter 0.2 and then play the clip.
So it's traveling five times slower than regular.
I'll stop that.
We'll go back to frame one.
Another way to retime a clip is to stipulate
the input and output range.
So we'll come up here, I'll turn on the input range,
and I'm going to say I want frame one to 20
to be mapped into, turning on, turning on, from one to 100.
So here I'm actually just stipulating what frames
I want to use, and it'll calculate the speed
for me here, 0.2, and here we go.
Playing at 20% speed.
Now the time warp thing is on this tab here.
This is a speed curve, if you will.
The horizontal axis represents the timeline
and the vertical axis represents the clip.
So for example, if I insert a control point
here and I pull the curve like this
this says go very slow at the beginning
and then speed up towards the end.
So I'll click play, slow, faster,
faster, faster, faster, faster, faster, faster.
There you go.
Here's another example.
I'll delete this control point, insert a new one right here.
Then I'll set the slope to be horizontal
right there in the middle of the curve.
That means it's going to go quickly,
come up to the middle of the timeline,
and pause zero speed and then take off again.
So let's watch that happen when I click play.
And at 50, there it is, that little pause right there.
Now there are two options for frame interpolation
so let's go back to the retime node
and we'll reset the knobs to default,
take a look at those.
I'm going to set my speed back to 0.2.
And set the play head on frame one.
The first option, the simplest option,
is a filter called nearest.
That means its just going to pick the nearest frame.
No filtering, no averaging, no nothing, no tricks.
So as I play the clip, you can see it's just
stepping through the frames one at a time.
If I jump back to frame one and I single-step
through it with the right arrow key,
step, step, step, step, two, step, step, step,
step, three, step, step, step.
All right, so that's the nearest.
Return the play head to frame one.
Now let's take a look at the box filter.
This will allow a rolling cross dissolve.
But to see the dissolve, we're going to have
to widen the shutter setting.
With the shutter set at one frame,
it's not going to average any frames together.
So my speed is 0.2, that is to say five
times slow, so I'm going to hold the shutter
open for five frames.
Now let's go back to our timeline
and I'm going to do another single frame
with the right arrow key.
One, two, three, four, five, six, one, two,
three, four, five, six, so you can see the cross dissolving.
Okay, now that we understand how it works
let's see how it looks on a clip.
This first retime node is set for the simple nearest.
And the speed is 25%.
So let's watch what happens when we slow a clip
down by that amount using just the nearest filter.
As you can see, that looks pretty step-y.
We'll stop that, go back to frame one.
Now we'll take a look at the frame averaging with this node.
Again, the same speed, 0.25, with the box filter
enabled and the shutter set for four frames.
And we'll play this.
There you can see the cross dissolving.
Not much better but at least it's not so step-y.
You may have noticed that neither of the two
examples of the walking boy look very nice.
That's because the retime node cannot generate
in-between frames for smoother motion.