1. Field of the Invention
This invention relates generally to processing of computer graphics for display on a television, and more particularly, to flicker filtering for computer graphics.
2. Description of the Related Art
As the result of the continuous development of new technologies, the distinction between computers, in particular computer monitors, and televisions is becoming increasingly blurred. In other words, the computer and television industries are converging. For example, computer networks such as the Internet and the World Wide Web used to be almost exclusively a computer phenomena. Now, however, televisions may also be used to access these networks. As another example, broadcast entertainment used to belong squarely in the television domain. Now, however, many service providers are offering entertainment to computer users through computer networks. As a result of this convergence, there is a need to display computer graphics originally intended for computers on televisions.
Televisions and computers, however, generally use incompatible graphics formats. For example, many formats for computer monitors and flat panel displays are non-interlaced. In other words, the entire frame of computer graphics is updated at once. In contrast, many common television formats are interlaced, meaning that the frame is divided into odd and even fields and only one field or half the frame is updated at a time.
As a result, in order to display computer graphics on a television, the computer graphics often must be converted from a (non-interlaced to an interlaced format). This conversion typically includes dropping lines of the display. However, this introduces undesirable visual effects as a result of the conversion from a non-interlaced to an interlaced format.
In addition to the conversion process, the prior art also performs flicker filtering to improve the image quality. Two common types of flicker filtering are 2-tap and 3-tap filtering, in which either two or three non-interlaced lines are combined to form each interlaced line. The prior art has attempted to accomplish flicker filtering by dropping lines in both even and odd fields to vertically make the non-interlaced image match the scans line common for interlaced displays.
However, there are two problems with the prior art approach. First, the prior art requires that flicker filtering and the conversion be performed serially, one after the other. Moreover, each process, flicker filtering and the conversion, requires its own hardware or a general purpose graphics processor with software to perform each process. Furthermore, the prior art does not provide a way to perform both 2-tap and 3-tap flicker filtering.
Thus, there is a need for approaches with the capability of implementing both 2-tap and 3-tap filtering. In addition, there is a need to perform these operations while minimizing hardware requirements.