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The autos are created by clicking on an automation curve to establish the time position for the new keyframe anchor point. The basic nature of these simple auto values make them primitive operations that are easy to apply when needed.
There are many automation curve types, and most are not normally visible or clickable. To make them visible, use the View pulldown, or open the Window → Show Overlays . This window allows toggling of the parameters in the View pulldown but is more convenient because you can leave the window up to change values quickly. If all of the automation curves are turned on, the timeline will be quite cluttered, and so usually only the parameters of interest are enabled during use. When keyframes are selected, they are drawn on the timeline over the tracks to which they apply. The keyframe is represented on the timeline as a little square on the curve, for example as in fade, or as a symbol as in a mask. This square, timeline attachment point, can be used for positioning by clicking on a keyframe anchor and using drag and drop to set the new position.
The automation keyframes include:
mute/play audio; camera translation x,y and zoom; projector translation x,y and zoom; fade blending; audio panning; overlay mode; mask point sets and sampling speed.
Except for the mask auto, the values are all simple numbers. Mute is different from the other autos in that it is simply a toggle of either on or off. Mute keyframes determine where the track is processed but not rendered to the output. An example usage would be to use auto keyframes to fade in a clip by setting the transparency to 100% at the first keyframe and adding another keyframe 5 seconds later in the timeline with a transparency of 0%.
The Keyframes pulldown on the main timeline is used for Cut, Copy, Paste, Clear, Change to linear, Change to smooth, Create curve type of Smooth, Linear, Tangent, or Disjoint, Copy default keyframe or Paste default keyframe. If you right click on a curve keyframe on the timeline, a set of options popup including the choices keyframe type (such as Fade, Speed, etc.), Hide keyframe type, Delete keyframe, Copy keyframe, smooth curve, linear segments, tangent edit, or disjoint edit.
Usually, the use of the keyframe values are more pleasing when the data varies smoothly between keyframe anchors on the timeline. This is useful in many cases that are familiar, like a video fade in/out, or audio pan between channels. To make the auto value change smoothly as the media is played, the keyframes auto values are points on curves that are created according to the design of the effect. Most of the primitive types can create anchor points on curves that are piecewise linear, smooth, sloped, or broken at the keyframe anchor points.
Curve smoothing is called interpolation and it uses keyframe point values and control values that determine how the curve will react at the time the media is played or rendered. Interpolation uses 2 keyframes to create a set of intermediates which are used as active values between the previous and next keyframe anchors on the timeline. The way the intermediate data is generated depends on the type of curve used to invent these values. CINELERRA-GG interpolates the intermediate values making the change happen smoothly and gradually over time. The simple linear mathematical formula for interpolation is: a×(1 - t) + b×t where 0≤t≤1 uniformly.
Autos are handled inside the main executable. Therefore CINELERRA-GG knows exactly what a particular Auto does, how to interpret it, and how it can be interpolated.
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