A video decoder in which 1) resolution quality can be improved for a given
bit count analog-to-digital converter, 2) a lower bit count
analog-to-digital converter can be used with substantially similar
quality or 3) a combination of improved resolution quality with a lower
bit count analog-to-digital converter can be done. In the preferred
embodiment, a DC bias is added to the video signal after the sync portion
of the composite signal has been received and prior to the active video
being received. This bias is then removed after the end of the active
video period. By applying this bias, the DC voltage level of the video
signals is actually reduced, so that the full scale value of the
analog-to-digital conversion process can also be reduced. Thus, compared
to using an unbiased signal, increased A/D converter resolution is
obtained. In an alternative embodiment, the sync portion can be biased
upwardly during the front porch and then be returned during the back
porch.