Blender-Handbuch: VSE Effekte

Diese Seite bezieht sich auf Blender v2.5

Speed Control

Der Speed Control-Effekt dehnt oder staucht den Videostrip, so dass er schneller oder langsamer läuft als normalerweise. Eine Geschwindigkeit kleiner als 1.0 lässt den Strip langsamer ablaufen, eine Geschwindigkeit größer als 1.0 entsprechend schneller. Läuft der Strip schneller, werden einige Frames verworfen.

Sie können Speed Control verwenden, um einen Videostrip beispielsweise mit einem Audiostrip zu synchronisieren.

Using Speed for a Slow-Motion Effect 50% Slow motion using Speed Control

Suppose you want to sssslooow your strip dowwwwwwn. You need to affect the speed of the video clip without affecting the overall frame rate. Select the clip and Add->Effect->Speed Control effect strip. Click to drop it and press N to get the Properties. Set the Global Speed to be the factor by which you want to adjust the speed. To cut the displayed speed by 50%, enter 0.50. Now, a 30-frame clip will play at half speed, and thus display only the first 15 frames.

If you want the remaining frames to show in slo-mo after the first set is displayed, Kcut the strip in two, offset the second part (because the first slow-mo will actually run for more time/frames than shown), and add another Speed control as shown to the right. When the strip on Channel 1, as modified by the sfx strip on Channel 3 finishes, the strip selected on channel 2 starts, as modified by its sfx speed control in channel 3. The trick in creating the second strip is to

   * Select the original strip and ⇧ ShiftDuplicate it. In this case, it is a 20-frame image set.
   * Drag the clone to half-way above the original and drop it.
   * Select the left handle (start), grab it, and move it over half-way. This changes the start frame offset; the strip will now start playing at frame 11 (relative to within itself)
   * Select the right handle (end), grab it and move it over half-again as much (in this case, 10 frames) This sets the duration to be 20 frames within your video.
   * Add a 50% Speed Control for the first strip, and a 100% speed control for the second. For the second strip, you are already telling blender to play 10 frames over a 20-frame duration, which is already half speed, so you don't need the speed control to slow it down anymore, just to scale the frames selected to the duration of the clip. 

That's it! Set your render to animate (in this example) all 40 frames.

Why not just extend the original clip out, you ask? Well, the Speed Control operates based on the number of frames it is going to show, divided by the number of frames it has to show them over. For example, if a strip has 20 frames in it, and you specify a speed factor of 50%, it knows it has to display 10 frames. If that strip is, say, stretched to cover 30 frames of video, it will play each of the 10 frames for 3 frames (3 x 10=30). Understanding the math will help you be effective and get the control to do what you want it to.

In very simple cases it will also work to just extend the original clip. This is a very nice feature intended for story boarding and for filling gaps. Add a speed control, ignore the IPOs and all the other parameters and just extend the right handle of the original clip. Remember that this is only possible, if the underlying clip ends at the right handle position. (If this isn't the case because you used the knife tool to create it, add a meta for the original clip first.).

Using speed control for frame matching

To get even finer control over your clip timing, you can use IPOs! This can be done in several ways.

   * In the default configuration, your IPO curve simply map input to output frame scaled down to the range of [0-100] [0-1] in IPO curve coordinates. This is enough, if you want to add simple flickering effects. 

The speed effect can do even more for you. You can do actual frame matching! That means: you have a certain position at which a certain frame should get displayed (maybe when matching your video track to an audio track) and blender will adjust the speed of the clip smoothly to make this happen.

   * You can disable scaling in X direction by clicking on "IPO-frame locking". That means: input frame numbers are identical to IPO curve X-coordinates.
   * You can disable scaling in Y direction by disabling "Scaling [0-1]". That means: output frame numbers are identical to the IPO curve Y-coordinates. 

After that, use the N-keys window fo the IPO-window to place your control points in a frame exact way. [edit] Changing video frame rates

You can use the speed control to change the frames per second (fps), or framerate, of a video. If you are rendering your video to a sequence set, you can effectively increase or decrease the number of individual image files created, by using a Global Speed value less than or greater than one, respectively. For example, if you captured a five-minute video at 30 fps and wanted to transfer that to film, which runs at 24 fps, you would enter a Global Speed of 30/24, or 1.25 (and Enable Frame Blending to give that film blur feel). Instead of producing 5*60*30=9000 frames, Blender would produce 9000/1.25=7200=5*60*24 frames. In this case, you set a Sta:1 and End:7200, set your Format output to Jpeg, 30fps, and image files 0001.jpg through 7200.jpg would be rendered out, but those images 'cover' the entire 9000 frames. The image file 7200.jpg is the same a frame 9000. When you read those images back into your film .blend at 24 fps, the strip will last exactly 5 minutes.