Improved interpolation of 4∶2∶0 colour images to 4∶4∶4 format exploiting inter-component correlation

The paper deals with the interpolation problem of colour images or video whose chrominance components are downsampled according to 4:2:0 scheme. Such interpolation is traditionally done using a linear 7-tap FIR filter which introduces some blurring and colour artifacts across the edges and details. The idea discussed in the paper is to improve the interpolation through adaptive filtering. The paper shows that strong higher-order correlation is present between luminance and chrominance channels regardless of the colour representation. This correlation may be exploited to support the interpolation of low resolution chrominance using fine detail information extracted from the luminance component of higher resolution. Experimental results show that the error due to the loss of high-frequency data in downsampling and subsequent upsampling is significantly reduced by the use of the proposed technique.