Human visual system features enabling watermarking

Digital watermarking consists of hiding subliminal information into digital media content, also called host data. It can be the basis of many applications, including security and media asset management. In this paper, we focus on the imperceptibility requirement for image watermarking. We present the main features of the human visual system (HVS) to be translated into watermarking technology. This paper highlights the need for dedicated inputs from the human vision community. The human visual system (HVS) is very complex and able to deal with a huge amount of information. Roughly speaking, it is composed of a receiver with a pre-processing stage, the eye and the retina, a transmission channel, the optic nerve, and a processing engine, the visual cortex. Mainly because of our lack of knowledge about brain behavior, i.e. about the way a stimulus is processed through its huge neural network, the large effort to understand and model the HVS behavior has partly remained fruitless. The aim of this paper is not to provide a thorough description of the HVS. For complete HVS models and more specific details, the reader is referred to existing literature. Here, we only try to understand, in a synthetic way and from an engineering perspective, the HVS features on which the designer of a watermarking algorithm can rely, i.e. its sensitivity and masking capabilities.