I'm using an ADV7513 to drive a DVI monitor. When I drive the monitor with a six foot cable the video is fine. When I drive the monitor with a twenty foot cable the colors are distorted. The are red lines that follow the contours of images in the video. If I test with a color bar test pattern the video is clean. I can't tell if it is a drive problem or a skew problem with the output. Any suggestion on how to resolve this would be appreciated.