Optimized Interpolation and Cached Data Access in LUT-Based RGB-to-RGBW Conversion

Abstract

In recent display panels, the RGBW color domain becomes popular because it improves the brightness of the display panel compared to the conventional RGB domain. An RGBW display system, in general, uses a look-up table (LUT) for fast RGB-to-RGBW conversion. However, a large-sized LUT is implemented in external memory, which slows down system speed and increases power consumption. For robust LUT-based RGB-to-RGBW conversion, this brief proposes two schemes. First, the data mapping of the LUT is sub-sampled. For fast conversion, the sub-sampled data are approximately interpolated. Moreover, the interpolation performance is improved by using a refinement scheme. Second, a small internal buffer that caches the information from the LUT is used for the conversion. When the information stored in the buffer is used for conversion, the access to the LUT of the external memory is skipped, thereby reducing the execution time during RGB-to-RGBW conversion. Experimental results show that the average of mean squared errors by the proposed sub-sampling and interpolation schemes varies from 0.00 to 21.72 when the quantization step is changed from 1 to 5, respectively. Compared to the trilinear interpolation, the proposed interpolation scheme reduces the number of accesses to the LUT from 8 to 2 and that of linear interpolation executions from 7 to 1. The proposed caching scheme with a 2.2 KB buffer reduces the execution time by 81.93%.