Table of Contents
Advertisement
Inputting sources that use film alpha, such as Avid (Invert Alpha option)
Video systems conventionally interpret an alpha channel value of 0 to indicate complete
transparency. Film systems conventionally interpret an alpha channel value of 0 to indicate
complete opacity. When importing a video source from a system that uses film alpha (such as
Avid), use the Invert Alpha option on the Input tab.
Set the field order (interlaced video clips only)
Interlaced video is divided into alternating fields, called upper and lower. Field order specifies
which field of interlaced video is drawn to the screen first. You must ensure that the field order
setting for each interlaced video clip is the same as that clip's native field order.
Standard-definition video (such as NTSC DV) is typically lower-field first, whereas PAL D1
and many high-definition formats (such as DVCProHD 1080i) are upper-field first. If you
choose the wrong field order for a clip, you'll see a comb-like edge around the subject and
stuttering with movement in the image.
Assign the video clip to the desired layer, and select it as the active layer.
1.
Select the appropriate setting from the Field Order list on the Input tab.
2.
Matching the aspect ratio of a basic set's background with a
session
Each virtual set has a native aspect ratio. In most cases, you should match the aspect ratio of
the set to the aspect ratio of the session that is specified on the Output tab. However, Ultra
lets you mix them if that suits your purposes.
Matching input clips and virtual sets
You should match each input clip with a virtual set that roughly matches the framing. For
most virtual sets, the title indicates the framing, with Tight, Medium, or Wide in parentheses.
The exceptions are VirtualTrak sets, which are designated as Trak, and sets where the input
clip appears as an inset, which have nothing in parentheses in the titles. For VirtualTrak sets,
you must preview the tracking shot to determine its framing. For sets that display the input
clip as an inset, any framing works.
Creating and assigning sources and virtual sets
65
Advertisement
Table of Contents
