1.The cause of bad video is a poorly adjusted TV.
The high fidelity of DVD video demands much more from the display.
Turn the sharpness and brightness down.
See also What's the quality of DVD-Video?
If you get audio hum or noisy video, it's probably caused by interference or a ground loop. Try a shorter cable, because long cables can degrade the signal. Make sure the cables are good quality with shielding. Try turning off all equipment except the pieces you are testing. Try moving things farther apart. Try plugging into a different circuit. Make sure all equipment is plugged into the same outlet. If all else fails, ground your braces and wrap your entire house in tinfoil.
2. Video or audio problems is a faulty player or bad disk . If the video freezes or breaks up, it may be caused by scratches on the disk. It's normal for DVDs to freeze for a fraction of a second in the middle of a movie — this is a layer break.