Inter-Layer Prediction of Color in High Dynamic Range Image Scalable Compression

International audienceThis paper presents a color inter layer prediction (ILP) method for scalable coding of High Dynamic Range (HDR) video content with a Low Dynamic Range (LDR) base layer. Relying on the assumption of hue preservation between the colors of an HDR image and its LDR tone mapped version, we derived equations for predicting the chromatic components of the HDR layer given the decoded LDR layer. Two color representations are studied. In a first encoding scheme, the HDR image is represented in the classical Y'CbCr format. In addition, a second scheme is proposed using a colorspace based on the CIE u'v' uniform chromaticity scale diagram. In each case, different prediction equations are derived based on a color model ensuring the hue preservation. Our experiments highlight several advantages of using a CIE u'v' based colorspace for the compression of HDR content, especially in a scalable context. In addition, our inter-layer prediction scheme using this color representation improves on the state of the art ILP method which directly predicts the HDR layer u'v' components by computing the LDR layers u'v' values of each pixel