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newbie here. I need some help with the Video Sequencer. I'm trying to change the speed control of a video accelerating and decelerating some parts and using curves to smoothen the effect. My problem is very basic, about keyframing.

I add the video, add the speed control effect strip, uncheck 'stretch input ...' and uncheck 'use as speed'. Then I keyframe the 'frame number' control in a specific frame with a specific 'multiply speed'. I repeat a with other frame.

The result is that the video shows as a still image, with some bumpy movementt at the keyframes that does not reflect the speed changes.

What am I missing? any help please?

thanks!

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    $\begingroup$ Convert your movie clip to an image sequence as compressed files don't work very well when being slowed down (the frame count can be confused), and don't expect smooth slow downs as Blender simply duplicates frames or drops them to achieve a specific speed. No frame blending occurs. $\endgroup$
    – 3pointedit
    Commented Sep 2, 2018 at 12:19
  • $\begingroup$ cool. thanks. I want to speed up and down to normal again, so no slo-mo really $\endgroup$
    – David Hurt
    Commented Sep 2, 2018 at 17:47
  • $\begingroup$ Not good slo mo anyway. $\endgroup$
    – 3pointedit
    Commented Sep 3, 2018 at 2:36
  • $\begingroup$ anyways, I'm still not able to keyframe correctly the Speed Control strip effect. When I start adding keyframes to the effect Frame Number it starts to do weird things. I'm pretty sure I'm not doing it right, and the fact that keyframing the effect property does not have a graphical representation does not help... $\endgroup$
    – David Hurt
    Commented Sep 3, 2018 at 9:26
  • $\begingroup$ Are you using a frame sequence instead of a movie clip? What value are you animating? Did you press the Refresh Sequencer button at the bottom of the VSE timeline? $\endgroup$
    – 3pointedit
    Commented Sep 3, 2018 at 20:33

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I recommend animating the Speed Factor value not the Frame Number. If you animate the frame number then you have to keep track of what frame you are up to. And you would have to generate an f-curve angle that constantly progressed at 1 frame per frame upwards.

Using the Speed Factor however you just animate the playback speed and ignore the Multiply Speed (in fact it can't be animated) which should be left at 1.00 (unless you want a global speed change for the clip).

VSE speed ramp

In the example above, the strip begins playback at full speed or 100%, or Speed Factor 1.00. Then when I want the video to slow down I place a new keyframe with the same value 1.00. This acts as a Hold value, so the media plays full speed up to this point.

Then I place a new key frame and makes its Speed Factor 0.00 or 0% speed. This pauses the video. If I move the 0% keyframe to the right, I create a slope in the f-curve, this is the deceleration, the steeper the slope the faster the deceleration. A vertical slope is the same as pressing pause.

The problem with this approach is that it is very difficult to land at exactly the right frame for your pause. That is why you may want to use the constant slope style of Frame Number.

In the Frame Number example notice that the curve must also be a vector or straight line, as a bezier curve will generate ramping that you might find undesirable (odd frame duplication).

Notice that I have placed a keyframe at the first frame and the end frame of the same values, 0 - 803.

VSE frame speed

To make a pause hold , you need to split and slide this f-curve so that its angle does not change. In this case I selected the middle keyframe (which I made at the exact frame that I wanted) and the last keyframe, then duplicated them and slid the right. I then deleted the first end keyframe.

VSE Frame speed pause

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    $\begingroup$ Thanks @3pointedit, you made my day. I've successfully created a boomerang video with accelerating and decelerating speed, very smooth. Here there's a sample of how the curves are: imgur.com/a/0iI43Ce <br/>The result goes from this (horrible speed changes) imgur.com/a/Lb7UGyQ to this (much better) imgur.com/a/R6Ckpfk $\endgroup$
    – David Hurt
    Commented Sep 10, 2018 at 15:34
  • $\begingroup$ This answer really rounded out my understanding of Speed Control in general and Frame Number animation in particular....to the point where I think your own statements about the difficulties are overstated...it's actually pretty straightforward. :) I find that for most circumstances pinning the start and end frame of the strip (or maybe a sub-segment) as first step makes life easy. It's usually simple to figure out what values to keyframe there. (Esp if net effect is strip has same duration as before.) After that you can freely experiment in the contained frames. $\endgroup$
    – B Layer
    Commented Nov 10, 2019 at 22:16
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    $\begingroup$ Note that I use "pin" here as a descriptive term only, it's not a Blender operation. You start by key-framing the start/end frames which, in effect, pins the endpoints of the strip/area you want to modify. $\endgroup$
    – B Layer
    Commented Nov 10, 2019 at 22:26

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