| abstract |
The perceived quality of a dithered or dithered/dedithered video signal can be improved under some circumstances by skewing the dither sequence. The dither sequence, whether a 1-bit or 2-bit sequence, repeats continuously on a given line but is phase shifted on different lines. Many possible skewing schemes are possible. Two skewing sequences can be particularly advantageous in hiding artifacts in the display due to the dithering process itself. One and two pixel, field to field skews are those in which all the lines of one field have the same phase and all the lines of the next field are skewed one or two pixels with respect to the first field. The field to field skews on 2-bit dithered signals work best for frozen pictures. Some line structure can be visible during live video, where there are flat areas in motion. The one pixel skew is particularly advantageous for 2-bit dithers if the signal will be dedithered, but the two pixel skew is particularly advantageous if the signal will not be dithered. Whether or not the signal should be dedithered depends upon the display format. |