Signal interference

[Larry S. evans ii]

There are a number of ways that you can produce “interference” type effects. First I will assume that your “TV” footage is a separate layer or separate comp, and second I take you desire to “not use a plug-in” to mean you don’t want to buy a third party effects filter if you can do it yourself. I’m a believer in that to a point. Many such effects are really presets that use the After Effects toolsets and allow you to tweak variables to get the look you want. But you might also consider that having such filters can save you time (and if you are producing on deadline-money) and that is usually eventually worth the cost.

That being said, I’d direct you to Aharon Rabinowitz’s tutorial here on making “old style” TV scanlines. If you are trying to simulate a modern digital set, you’ll need to find some combination of the built-in filters that generates the random blocks that we see when the satellite goes out, but the base principles are the same.

You will also find useful the “hologram” tutorial over at Videocopilot.net. Although it is designed to simulate the Star Wars sort of effect, it includes some ways of creating distortion that may be helpful.

Otherwise, it’s really merely a matter of creating a matte or alpha channel that can be used to mix the two different video sources the way you want them.

That is, in terms of the old scan-line approach, you may find that modifying the height of horizontal gridlines interactively, and then using the results as a luma matte will cause portions of the interferring video to become more or less visible over the original.

Alternatively, you could use solids of different sizes and move then up and down on the “screen” to generate “breakthrough”. If you make them white or gray against black, then the resulting contrasts become your luma or alpha matte, and you could then pre-render this out to a clip for use. The same idea applies to “digital” blocks.

If you are looking to distort left to right, the mesh warp filter is a fairly organic approach, but you might also find using Time Displacement can give you some interesting effects.

You might also want to take a look at the Digieffects plug-ins Delirium and Damage. Delirium includes some general video distortion effects among others, and Damage is specifically designed to create the look of “bad video”. Even if you want to do it “by hand”, the movie samples shown for these plug-ins may help you crystalize your own vision of the effect.

Ultimately it comes down to a intuitive approach. You see what it is you are expecting in your head already. Now you just have to start putting together the pieces to make it look like that. I hope some of these suggested tutorials will help.

Larry S. Evans II
Executive Producer
Digital I Productions