AfterDawn: Glossary

Global Motion Compensation

Global Motion Compensation, or GMC, is a technique used in MPEG-4 encoding that allows greater compression for scenes with camera pans and other motion that affects the entire video frame simultaneously. By contrast, older formats like MPEG-2 always use separate calculations for each 16x16 pixel block in the frame, requiring more bits.

Due to the increased complexity of GMC over standard block based motion estimation, hardware MPEG-4 encoders often don't support it, making it risky to use for encoding in many situations. There are also differences in how its implemented in different MPEG-4 codecs, with DivX using a much simpler version than XviD. GMC complexity can be determined by the number of warp points supported. DivX uses a single warp point, while XviD can use up to three. Most hardware that supports GMC is only capable of rendering video with 1 warp point.

Related guides:
How to play MP4 files
How to play AVI
Convert DVD to XviD with meGUI


Related glossary terms

Related software tools

Rating: 3.11
Rating: 2.75
Shareware for Windows Rating: 3.09
Shareware for Mac Rating: 2.50
Freeware for Windows Rating: 3.15
Shareware for Windows Rating: 3.06
Shareware for Windows Rating: 3.06
Freeware for Windows Rating: 3.30
Shareware for Windows Rating: 4.67
Freeware for Linux Rating: 3.19
Shareware for Mac Rating: 3.06
Shareware for Windows Rating: 2.91
Freeware for Mac Rating: 2.93
Freeware for Windows Rating: 3.20
Freeware for Windows Rating: 3.27


Select a term to see the explanation