QLab 5VideoFading Video and Video Effects

Fading Video and Video Effects

The Fading Video tutorial is a hands-on exploration of the topics discussed in this section.

A Fade cue can be used to adjust the geometry and video effect parameters of a targeted Video, Camera, or Text cue. Fade cues can also adjust audio parameters of Video and Camera cues. When a Fade cue is selected, the inspector will only show the tabs relevant to the type of cue that the Fade cue is targeting.

The word “fade” can often be taken to mean one thing or another, but in QLab “fade” simply means “change a value over time.”

Fade cues require a cue target, have a duration, and must adjust at least one level or parameter of their cue target in order to be considered functional.

The Inspector for Fade Cues

When a Fade cue which targets a Video cue or Camera cue is selected, the inspector shows the Basics tab and Triggers tab, used by all cues, as well as the following tabs:

The Curve Tab

The fade curve, drawn in yellow on the right side of the tab, determines the rate of change of the parameters being faded. The curve on the left is for levels which increased by the fade, and the curve on the right is for levels which are decreased by the fade.

The horizontal axis of the curve represents time and the labels across the top will change based on the duration of the Fade cue. The vertical axis represents percentage of the total change made by the Fade cue. For the rising curve, the one of the left, the bottom left corner represents the beginning of the fade, which is to say “time = 0, completion = 0%.” The top right corner represents the end of the fade, or “time = (duration of the Fade cue), completion = 100%.” For the falling curve, the top left corner represents the beginning and the bottom right corner represents the end.

The curve shape that appears by default is set according to the Fade cue’s cue template, but you can choose another fade shape from the pop-up menu in the top left corner of the tab.

The Curve tab

There are four options for Fade curve shapes:

  • S-Curve. QLab’s default curve shape follows an “ease-in, ease-out” envelope designed to sound natural with audio levels and look smooth with video geometry.
  • Custom Curve. This option allows you to click anywhere along the fade curve and a create control points, which can be dragged to change the shape of the curve. Moving control points will smoothly bend the curve in the direction of the control point. To delete a control point, click on it to select it and press the delete key on your keyboard. To start over entirely, click Reset to Default Shape in the bottom left corner of the tab.
  • Parametric Curve. This option adds a text field labeled Intensity below the pop-up menu which allows you to use a mathematically precise parametric fade shape.
  • Linear Curve. This option is similar to the custom curve option but instead of smoothly ending the curve, control points create a precise, sharp bend. To delete a control point, click on it to select it and press the delete key on your keyboard. To start over entirely, click Reset to Default Shape in the bottom left corner of the tab.

Both the rising and the falling curve use the same fade shape type, but if you use custom curve or linear curve you can create individual curve shapes for each.

The Audio Domain pop-up menu is only relevant if the target cue contains audio and if anything pertaining to audio is being faded. You can learn about this control from the Fading Audio section of this manual.

The Levels Tab

The Levels tab will only appear if the target cue contains audio. It behaves the same as the Levels tab for Fade cues targeting Audio cues.

The Geometry Tab

The Geometry tab allows you to specify which parameters of the target cue you wish to fade, and what their final value will be.

The Geometry tab

The left side of the Geometry tab contains a few setup tools:

Clicking the Set Geometry from Target button, or using the keyboard shortcut ⌃⌥⌘V, will invoke the paste cue properties sheet in a special way. First, it will behave as though the target cue was selected and copied, and second it will automatically select the “Video” set of properties to paste. You can choose other properties if you like, but if you simply hit the enter key, QLab will paste the geometry from the target cue onto the Fade cue. This is a convenient way to get started building a fade, as it will help you keep track of the starting point from which you will be fading.

Stop Target When Done. If this box is checked, the target cue will stop once the fade is complete. If the box is unchecked, the target cue will continue to run after the fade is complete.

Absolute Fade. This drop-down menu lets you choose between an absolute fade, which is QLab’s default, and a relative fade. Relative fades are discussed in detail below.

Preview. This button provides quick access and a visual reference to the live fade preview setting.

The center section of the Geometry tab contains controls for the fade-able parameters of a Video, Camera, or Text cue. By default, the checkbox next to each parameter is unchecked which means that the Fade cue will not adjust that parameter. To “activate” a parameter, so that the Fade cue will adjust it, check the box next to that parameter.

Opacity. You can fade the opacity of the target cue to any whole-number opacity between 0% and 100%.

Translation. You can move the target cue left to right and up to down by fading translation. Change the position of the video along the X-axis and/or Y-axis by entering values in the text fields or by clicking and dragging the thumbnail image in the preview box to the desired location.

Scale. You can scale the target cue in both the X and Y axes together, or individually by clicking the icon to unlock the axes and adjust them separately. You can also adjust the scale by scrolling vertically on the thumbnail image in the preview box.

Rotation. Click and drag on each of the (X), (Y), and (Z) buttons to fade the rotation of the target cue.

3D orientation. By default, Fade cues use three-dimensional quaternion math to rotate their target. This results in smooth, natural movements when rotating along multiple axes, but necessarily means that a fade will never pass through more than 180 degrees of movement in each axis. If you instead want to rotate the target a specific number of degrees about a single axis, you can use this pop-up menu to choose an axis, and then enter the number of degrees you wish to rotate.

Reset. Clicking the Reset button will zero out the rotation values in the Fade cue on all three axes, which means the Fade cue will rotate its target cue to the default “front facing” rotation.

The right section of the Geometry tab contains a blue preview box, representing the stage that the target cue is assigned to, and a thumbnail image of the target cue.

The Audio FX Tab

The Audio FX Tab tab will only appear if the target cue contains audio. It behaves the same as the Audio FX tab for Fade cues targeting Audio cues.

The Video FX Tab

Fade cues automatically recognize video effects added to their target cues, and list all of the parameters of all of the video effects in use. By default, the checkbox next to each effect parameter is unchecked, which means the Fade cue will not adjust that parameter. To fade a parameter, just check the box next to that parameter. Fade cues can adjust any number of parameters simultaneously.

Clicking the Set Video FX from Target button will set all video effects parameters to the levels that they contain in the target cue. This is a convenient way to get started building a fade, as it will help you keep track of the starting point from which you will be fading.

Checking the box labeled Fade rate to, and setting a target rate, allows you to fade the playback rate of the target cue. The maximum playback rate in QLab is 33, or 33× normal speed, and the minimum is 0.03. This control has no effect on Camera or Text cues.

Stop Target When Done. If this box is checked, the target cue will stop once the fade is complete. If the box is unchecked, the target cue will continue to run after the fade is complete.

Preview. This button provides quick access and a visual reference to the live fade preview setting.

Relative Fades

By default, Fade cues are Absolute. This means that any parameters that you adjust with a Fade cue will arrive at their final levels regardless of their status before the Fade cue runs. If you use a Fade cue to set the scale of a target Video cue to 2, then the scale of that Video cue will end up at 2 after running the Fade no matter where that level was set to begin with.

However, using the pop-up menu on the left side of the Levels tab or Geometry tab, you can set a Fade cue to be a relative fade. Instead of setting levels to a specific value, relative fades either add or subtract a given amount or multiply or divide a given amount from, to, or by the active parameters, so the starting point of those parameters very much matters. When set to relative, the cue’s icon changes to the relative form.

The Geometry tab - relative fade

In this screen shot, the Fade cue has its scale set to 0.9 which has the effect of reducing the size of the target to 90% of its current size. If you ran the Fade cue three times, the cumulative result would be reducing the size of the target cue to 72.9% of its original size, since each time the Fade cue runs, it causes a 90% reduction of the then-current size.

Relative opacity changes are similarly multiplicative; a relative Fade cue set to an opacity of 90% will reduce the opacity of its target by 10% of its then-current opacity.

Relative translation and rotation changes are additive, so a relative Fade cue set to an X-axis translation of 100 will add 100 pixels to the X-axis translation of its target each time it runs.

Relative fades which adjust 3D rotation or video effects can have results which are difficult to predict, and so this manual will refrain from making blanket statements about them.

In QLab 4, using absolute Fade cues on a parameter that had previously been adjusted by relative Fade cues could have unpredictable results. In QLab 5, however, absolute fades supersede relative ones. In QLab 5, an absolute fade is absolutely more absolute.

Reverting Fades

QLab has a sort of special-case undo command that applies only to Fade cues, called Revert Fade Action. You can find this command under the Tools menu when a Fade cue is selected, or you can use the keyboard shortcut ⇧⌘R.

When Revert Fade Action is invoked on a Fade cue after that Fade cue has been run, QLab reverts the levels of that Fade cue’s target to whatever they were before the Fade ran except for levels which have been otherwise changed. That is to say, the only adjustments that are reverted are the ones that the selected Fade cue caused.

Broken Fade Cues

Fade cues can become broken for the following reasons:

Missing cue target

Assign a target cue to this cue.

No parameters set to fade

Set this cue to adjust at least one parameter. You can enable or disable an audio parameter by clicking in it; active controls will be highlighted in yellow. You can enable or disable a video parameter by checking or unchecking the box next to it.

Missing cue audio effect

Either install the missing audio effect and restart QLab, or remove the missing effect from the Audio FX tab of the inspector of the target cue.

License required

An audio or video license is required to fade playback rate, fade audio effects, or use Timecode triggers. A video license is required to fade video geometry or video effects. Install the appropriate type of license or adjust the cue to avoid using licensed features to clear this warning.

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