Very low bit-rate video coding using arbitrary shaped patterns to represent moving regions in macroblocks has very good potential for improved coding efficiency. For any pattern based coding similarity threshold is used as a matching criterion between a moving region and a pattern. This metric together with quantization can control the coding efficiency curve. Unlike the quantization step size, the benefit of this metric is that it does not need to be transmitted any information in the decoder. Finer changes of coding efficiency curve can be possible by changing the similarity threshold instead of changing the quantization level, as a result a number of bits will be reduced. In this paper, we investigate the coding efficiency curves of different similarity thresholds.