[citation needed] It is used in many modern video coding formats such as MPEG-4 ASP and H.264/AVC.
[1] Though higher precision motion vectors take more bits to encode, they can sometimes result in more efficient compression overall, by increasing the quality of the prediction signal.
Quarter-pixel resolution can improve the quality of the video prediction signal as compared to half-pixel resolution, although the improvement may not always be enough to offset the increased bit cost of the quarter-pixel-precision motion vector; additional techniques such as rate-distortion optimization, which takes both quality and bit cost into account, are used to significantly improve the effectiveness of quarter-pel motion estimation.
Different specific schemes are used in different designs: Videos encoded with quarter-pixel precision motion vectors require up to twice as much processing power to encode, and 30-60% more processing power to decode.
As a result, to enable wider hardware compatibility, Qpel is disabled in the default DivX encoding profiles.