An Introduction to Video in QLab 3
QLab 3 uses AVFoundation to render video which is a change from the video engine used in previous versions. Applications such as iTunes11 and Final Cut X use this engine as well. Media which worked in previous versions may not work in QLab 3.
Supported Video Codecs:
| Abbreviation | Codec | Notes |
|---|---|---|
| mp4v | MPEG-4 | |
| mp2v | MPEG-2 | |
| mp1v | MPEG-1 | |
| apcs | ProRes 422 LT | Recommended for general use. |
| apco | ProRes 422 Proxy | |
| apcn | ProRes 422 | |
| ap4h | ProRes 4444 | Use for videos with an alpha channel (transparency). |
| avc1 | H.264 | |
| apch | ProRes 422 HQ | |
| h263 | H.263 | |
| jpeg | Photo-JPEG | |
| dv5p | DVCPRO50 PAL | |
| dvpp | DVCPRO PAL | |
| dvcp | DV PAL | |
| dvc | DV/DVCPRO NTSC |
It should be noted that the extension at the end of a media file is merely a wrapper and not an indication of the video codec contained. A wrapper is similar to a box as it is just holds the content with in it. A wrapper can hold many different types of contents such as video and audio which are encoded with a codec by the publisher of the video in order to reduce the size of the file and then decoded by QLab.
It is best to create content which matches the size of your video surface(s) although not a requirement.
Syphon Support [Pro Video or Bundle]
QLab 3 has support for the open-source framework Syphon. This enables QLab to ingest and deliver full-frame video to/from other syphon-enabled applications. Available Syphon inputs will automatically appear as camera cues and Syphon Outputs can be created when setting up a video surface.
Camera Input Support
Up to eight Live Camera feeds can be brought into QLab via Firewire, USB, Thunderbolt, or PCI Bus Devices. QLab 3's camera cue provides access to all current Blackmagic Design DeckLink, Multibridge and Intensity products (as of October 2013).
Other Tested Devices:
| Make | Model |
|---|---|
| GrassValley | ADVC-55 |
Video Surfaces
Video surfaces reflect your multimedia scenario and make programming quicker in multiple-device configurations. Surfaces are made up of screens whcih are the projectors, televisions, and other output devices you will use in your production. Video surfaces have buit-in edge-blending and the ability for custom corner-pinning .
Getting Started
Setting your desktop backgrounds to black
QLab outputs video atop the desktop of attached displays so when there is no video playing then the desktop background is visible. To set your desktop backgrounds to black click on Tools and then Blackout Out Desktop Backgrounds .
Diving Into Video Settings
Click the Settings Icon [the sprocket in the bottom right of QLab] and then click on the Video section.
Default Mode - Full Screen vs. Custom Geometry
There are two operating modes when using QLab for Video - Full Screen and Custom Geometry.
Full Screen - automatically scales and positions video content to fit within your selected video surface
Custom Geometry - allows you to choose an exact position video along the X,Y, and Z axis and choose the the scale of your content.
There's no wrong answer and either mode can be selected on individual cues. This setting is just choosing which modes new cues will default.
Creating a Video Surface
Click the + icon at the bottom left of the Video Settings window to create a new surface. Click "Edit" next to the new surface to open the Surface Editor.
Click the + icon in the surface editor to add the displays you wish to be a part of this surface.
Dimensions - Width and Height in pixels of the total size of the video surface.
Partial Screens [Matrox2Go Products..etc]
Partial Screens are useful when using display expanders such as Matrox TripleHead2Go devices. QLab breaks displays into Virtual Screens and allows you to perform edge blending and corner-pinning for each display attached to the display extender. Partial screens support up-to a four-wide configuration with each attached device.
Syphon
Adding a syphon screen will allow QLab to mirror the surface to another syphon-enabled application. You can only add one syphon screen per surface but can use multiple screens for multiple syphon outputs.
Tip: Syphon is a valuable tool in pre-programming because it can stand-in for a physical device. If you need two displays then add two surfaces with syphon and use the Syphon Simple Client and Recorder application as preview monitors.
Bonus Tip: If you need complex projection mapping you can use QLab's Syphon output in conjunction with MadMapper
Adjusting Screens
To assist with the adjustment of screens each screen has the ability to display a test pattern by checking the Grid text box to the right of the screen.
- QLab's Test Grid has Large and small pixel boxes to help with masking and positioning
- Large boxes are 128 x 128 pixels
- Small boxes within large boxes are 32 x 32 pixels
When a screen is selected on the left column you can adjust the following settings
Origin - the position (X,Y) in pixels in which the screen is located within the surface.
- (0,0) is the bottom left corner
Rear - flips the screen output horizontally to facilitate rear-projection
Ceiling - flips the screen output vertically to facilitate ceiling-projection
Corner Pin - drag the yellow dots on the outside corners of a screen inward to fix projector keystone effects.
- Note: You are not able to go outside the boundaries of a surface with corner pin.
- Click Reset Corner Pin to reset corner pin positions to their defaults
Mirroring Displays
If two or more displays within a surface overlap more than 90% then their outputs will mirror.
Edge-Blending
A common technique to create larger projected images is to overlap two or more projectors. When displays overlap within a surface, QLab automatically creates a gradient between screens to perform edge blending in order to create a seamless image.
Blend Gamma - This is the adjustment of the edge-blend gamma per surface.
Note: the higher the gamma value the darker the blend
Using Shutters
Note: since version 3.1.7, “shutters” have been replaced by “constraints” thus we can no longer drag edges of the surface. Following paragraph is therefore deprecated.
Dragging the outside edges of the suface window inward allows you to shutter parts of the image. Masked sections will appear darker to indicate a shutter has been pulled in.
Advanced Masking
Save grid image... - This action saves a copy of surfaces' grid image in PNG format to aid in masking. The image exported will not have an indication of the screens being used - only the total area of the surface.
- Open up the grid image in your favorite image editing application (I am using Photoshop in this example)
- Create a new layer and use the paintbucket tool to fill the background white
- Use the grid as an aide in your masking or import your own test pattern
- Create additional layers with black shapes in order to mask-out the sections of the image you wish to avoid.
Hide the Test Pattern and save the file.
- If the test-pattern isn't hidden then it will appear in all cues
- Remember to keep your white background or else no video will pass through!
Save the image as a PSD or PNG file
Mask Image - double-click the blank area and browse to your mask image or drag your mask from Finder into this area.
You can continue to edit your mask in another application and Qlab will automatically pull changes from this file.