User Manual

However, if you need to disable or alter the interpretation of an alpha channel for any clip, for
example if a clip is being interpreted as having an alpha channel of the wrong type, you can
right-click that clip, choose Clip Attributes from the contextual menu, and use the Alpha Mode
pop-up menu of the Clip Attributes Video panel to correct the problem.
NOTE: If you’ve imported clips with alpha channels, those alpha channels can be
rendered back out for Round Trip workflows if you set Render to Individual Clips in the
Deliver page, choose a Format and Codec combination that supports alpha channel
output, and turn on the Export Alpha checkbox in the Video panel of the Render
Settings list.
Keying, External Mattes, and
Window Compositing
It’s also possible to use the Qualifier, Power Window controls, and External Matte clips in the
Color page to create compositing effects by connecting a key that you create to the optional
Alpha output that can be added to the Node Editor. In this way, you can pull a simple
greenscreen key using a qualifier, do rotoscoping or matte work using a Power Window, or use
an external matte to composite two or more clips together, and see these effects on the
Edit page.
For more information on the use of the Alpha output to do node-based compositing, see
Chapter 126, “Combining Keys and Using Mattes.”
Transform and Cropping
DaVinci Resolve is a resolution-independent application. This means that, whatever the
resolution of your source media, it can be output at whatever other resolution you like. This also
means that you can freely mix clips of any resolution, fitting 4K, HD, and SD clips into the same
timeline, and scaling each to fit the project resolution as necessary.
Your project’s resolution can be changed at any time, allowing you to work at one resolution,
and then output at another resolution. This also makes it easy to output multiple versions of a
program at different resolutions, for example, outputting both HD and 4K sized versions of the
same program.
DaVinci Resolve has a powerful toolset for making geometric transforms, using advanced
algorithms for optical-quality sizing operations. Within the Edit page, each clip has a set of
transform parameters, principally for use in storing sizing data imported from AAF or XML when
you turn on the “Use sizing information” checkbox. This has the advantage of keeping these
imported Edit Transform settings separate from the Input Sizing parameters found on the Color
page, which are typically used by the colorist to make pan and scan adjustments of
various kinds.
Of course, you can also use these controls to create your own adjustments while working in the
Timeline, zooming into clips, repositioning them to improve the composition, and so on.
While there is some overlap between these parameters and those in the sizing palette of the
Color page, they’re both separate sets of parameters, so you can keep each set of
adjustments separate.
Chapter – 41 Compositing and Transforms in the Timeline 826