Combining SD and HD Video
Many video producers find that they need to combine HD footage with SD footage, or
combine several HD video sizes, within the same project. Converting a video format to a
higher-resolution format is called upconverting, and the reverse is called downconverting.
The process of upconverting and downconverting is not as simple as scaling a video
frame. Changes in aspect ratio (4:3 for SD and 16:9 for HD), frame rate, and scanning
method (interlaced and progressive) may also be involved.