1. An adaptive quantization method in a coding process for coding data values corresponding to each picture element (pel) of a portion of a video frame, the method comprising the steps of: selecting, for each portion of a video frame, a quantizer set R.sub.x of quantizer values from a group of quantizer sets R.sub.0 -R.sub.n, where each quantizer set differs from each other quantizer set in the group; traversing a trellis of decision levels corresponding to each of the quantizer values in the quantizer set R.sub.x and values for runs of consecutive zeros; correlating each data value with a decision level in the trellis; and determining an optimal path through the trellis based on distortion and bit rate characteristics provided by the decision levels.