Effects on the timeline


As promised on my post about transitions, here is how effects work. Effects are very similar to transitions, except that instead of having two inputs they just have one input. They take the video frames in, apply whatever effect they’re implementing on the frames and then send them to the output.

For the following diagram I created a timeline in which I dragged a single clip down and added an effect to it. For brevity I’ve removed the rest of the graph, but it just contains the source filter, video decoder, and frame rate converter that I described before. Here’s the part that deals with the effect.

 

As you can see, the video frames come in to Input 3 and they’re then sent to Output 1 which sends them to the effect code. The effect does its magic stuff on the frames and sends the results to Input 4 of the switch. These frames are then delivered to Output 0 as the output of the timeline and lo and behold you now have a video playing with an effect dynamically laid on top of it.

Comments (2)

  1. rehan says:

    This is great info. It also sort of confirms my suspicion that a "reverse video" effect is not possible via the custom effects mechanism in MM. What do you say about this?

    Now please dont forget to write about the resize problem. Also I will be grateful if you can say something about non-square pixel encoding as used in DV AVI profile and other NTSC/PAL profiles. Would the early resize step resizes the frames to fit to the display size such as 640×480 or the encoding size of 720×480? If 640×480 then wouldn’t it again be resized when encoding to 720×480?

  2. Dean Rowe says:

    Yes you’re correct, you wouldn’t be able to write a reverse effect with the way things are today. I’ll try to post a comment out resize soon.

    Cheers

    Dean.