A frequency adaptive line compression system for mobile display devices

Abstract

The high resolution of the latest high-performance mobile display devices has resulted in an increase in the main frame buffer size and related bandwidth, and this is one of the main causes of a reduced battery life. As a means to solve this problem, one-dimensional line-based compression methods have been studies in order to be implemented in the limited chip design environment of the mobile display driver ICs. Conventional lossless compression techniques do not have a high compression ratio enough for complex images to ensure a sufficient power reduction. On the other hand, a wavelet-based 1D SPIHT method has been studied for use as a lossy-compression method with a high compression ratio while keeping the image quality. However, this method requires large hardware resources due to the performance for iterative calculations and sorting process. This paper proposes a novel wavelet-based lossy compression system that can achieve high compression and image quality while maintaining low complexity. The Frequency Adaptive Line Compression composed of 4-level DWT, horizontal predictive coding for the low-frequency regions, frequency selective zero-zone quantization for high-frequency regions, and frequency component entropy coding. Experimental results confirmed that the proposed technique could achieve a higher compression ratio than the one required of conventional lossless compression methods and could also be implemented with a significantly less complexity than the conventional SPIHT method at the same compression ratio.