User:CompVisExp/sandbox

= Definition = 'Screen content' is a term for images showing content that can be seen on computer screens during typical office work. This term is mainly used by the vidio compression community.

Unlike video data captured by video cameras, computer screens usually display text and graphics combined with pictorial elements. Text and graphics are also referred to as 'computer-generated', 'born-digital', or 'synthetic', while pictorial elements such as photographs or medical images (e.g. X-ray images) are called 'natural'. Note that computers can generate photorealistic images that appear natural. A former term for images that contain a mixture of synthetic and natural elements was 'compound images'.

Synthetic data is characterised by a small number of different colours and repetitive patterns. Natural images usually do not contain sharp colour or intensity edges but varying colour gradients. This is mostly combined with a certain amount of noisy texture.

= Dealing with screen content =

Applications dedicated to screen content
Main applications for processing screen content data include web-based application sharing and desktop sharing. Other keywords are 'virtualized desktop' or 'thin client'. The idea behind this is the 1:1 transfer of screen content from a computer to a remote display. .

Compression of screen content
The Video Electronics Standards Association (VESA) undertakes activities on display stream compression (DSC). The latest standard for video compression, High Efficiency Video Coding (HEVC), contains several tools for the treatment of synthetic image content which are summarised as 'screen content coding' (SCC). There are some academic-driven efforts to improve the compression of screen content as, for example, towards its efficient lossless compression.

Quality assessment
The quality assessment of screen content has high importance because the digital modification of synthetic image data (e.g. by lossy compression) leads to higher visual degradation than the modification of pure natural image data. Dedicated compression schemes must take the human visual system into account and should try to get a good compromise between high compression ratios and low quality degradation.

= References =