1. A method for encoding video data, said method comprising: encoding a portion of the video data; generating a metric, said metric measuring complexity of the portion of the video data; and encoding another portion of the video data, wherein a rate of encoding said another portion of the video data is based on the metric, wherein generating the metric is comprised of: generating a complexity metric estimate; generating an actual complexity metric; and generating the metric based on a difference between the complexity metric estimate and the actual complexity metric.