Table of Contents > Cues > Camera Cue
QLab Documentation
This page last modified: 25 Apr 2011 12:14:52 PM.

Camera Cue

QLab 2 supports live video feeds directly in your workspace using any FireWire camera. Camera Cues operate just like Video Cues, except they have no audio.
By default a Camera Cue will run until it is stopped. If you enter a non-zero action time for the cue, it will run for the duration you specify.
Please note that display latency can vary dramatically depending on the video camera you use. QLab displays each frame as soon as it is received, so you may need to experiment with different cameras to find a device which meets your latency requirements.
Camera Cue Subtopics:

Settings


A Camera Cue in full screen mode.

Camera

Use the Camera patch to pick which input device will be used for the Camera Cue. Camera numbers are assigned to physical cameras in the workspace preferences.

Opacity

The opacity specifies the initial visibility of the cue. For example, if you wish to fade in the cue you would set it to 0% so it would start out invisible. Then you would use an Animation Cue to fade it in to 100% opacity.

Layer

The order in which video frames are drawn is specified by the layer. A Camera Cue with a higher numbered layer will be drawn over cues with a lower numbered layer.
Entering "top" means the Camera Cue will be displayed over all other previously fired cues. The most recent cue in the "top" layer is always displayed on top.

Screens

The screens buttons allow you to select which screens your Camera Cue will use. Note that the screen numbers are like Camera patches: the actual map from number to physical device is set in the workspace preferences. So "Screen 1" can be any device connected to your computer, or no device at all. The actual device is set by how you have mapped "Screen 1" to a physical screen in the workspace preferences.
The tooltip for each screen button will show the name of the actual physical screen currently assigned to that number. Hold your mouse over the button for a moment to see the tooltip.
As noted in the Video Cue performance tips above, your Camera Cue will perform optimally when it is assigned to only one screen.

Full Screen Mode

When a Camera Cue is in full screen mode it will be displayed on all the selected screens. You may optionally preserve the aspect ratio or stretch the camera image to completely fill the screens.

Custom Geometry Mode


A Camera Cue in custom geometry mode.
When a Camera Cue is in custom geometry mode you can customize the translation, scale, and rotation of the camera feed.
You can use the stage interface to modify these parameters visually. Click anywhere on the stage and drag to adjust the translation. Click in the rotation bar handle and drag to adjust the rotation. Use the scroll wheel on the mouse to adjust the scale.
By default the X and Y scaled are locked to the same value. Click the lock button to toggle this setting on and off.
If you enter a negative value for the scale, QLab will flip the camera image along that axis.

The Stage

QLab 2 introduces a concept called the video stage. Instead of positioning your videos directly on the screens, you position them on the video stage. This allows you to more easily move a video workspace to a new computer with different screens.
The video stage GUI displays all the screens currently attached to your system. The screens selected for this cue are outlined in yellow. The camera cue itself is displayed as a translucent yellow rectangle with yellow borders.
The light white crosshairs indicate the global origin of the stage. This origin is set in the Video Cue preferences. This origin is used if, for example, you want to display all your videos centered on a different screen. Instead of moving individual cue to the new screen you can just change the origin of the stage.
Click anywhere on the stage and drag to adjust the translation. Click in the rotation bar handle and drag to adjust the rotation. Use the scroll wheel on the mouse to adjust the scale.

Composer


QLab provides flexibility by allowing you to use a custom Quartz Composer file to render the camera feed. By creating your own compositions, you can apply Core Image filters, render your feed in 3D, and apply even more complex animations.
QLab will provide your Quartz Composition frames from the camera feed as it runs. To receive the frames your composition must publish an "Image" input port. Other ports you may publish include "xPosition", "yPosition", "Width", "Height", "Rotation", and "Opacity". (Opacity is passed as a color.)
To learn how to use Quartz Composer with QLab, try downloading this example Quartz Composer file. It will work with QLab "out of the box", and you can modify it however you like.

Preferences


The preferences panel for Camera Cues allows you to map camera numbers to physical camera. To map a camera number to a physical camera, click on the number you wish to map and drag the patch connector to the desired display device. You may have more than one camera number assigned to the same camera.
The screen numbers and global origin used by the Camera Cue are specified in the Video Cue preferences.
© 2010 Figure 53, LLC. All rights reserved.