Power consumption is very critical for portable video applications such as portable videophone and digital camcorder. Motion estimation (ME) in the video encoder requires a huge amount of computation, and hence consumes the largest portion of power. We propose a novel method of reducing power consumption of the ME by adaptively changing the pixel resolution during the computation of the motion vector. The pixel resolution is changed by masking or truncating the least significant bits of the pixel data, which is governed by the bit-rate control mechanism. Experimental results show that on average more than 4 bits ran be truncated without significantly affecting the picture quality. This results in more than 60% reduction in power consumption.
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