| JCTVC-B084 [C. Lan, J. Xu, F. Wu, G. J. Sullivan (Microsoft)] Screen content coding
Screen content (computer generated, not camera generated) was not explicitly mentioned in the HEVC project requirements. Such content reportedly has very different statistics – no noise, sharp edges, smooth motion. Two new coding tools were proposed: Residual scalar quantization (intra prediction, bypassing the transform, scalar quantization with deadzone like APEC in KTA); index map for colors (like vector quantization); each block represented by 1-4 colors and index.
The proposed tools were implemented in the JM; and the results reportedly show for one image "mix" and a normal webpage gain around 10 db vs. TMuC; less for a PowerPoint presentation slide.
It was remarked that it would be more interesting to also test with other material, e.g. animated graphics, mixture of video and graphics, scrolling text etc.
It was remarked that adapting QP might help for HEVC.
Was comparison made against GIF, JPEG-XR? No
Would it be a good idea to burden any decoder by implementing these tools?
It was remarked that other standards bodies (Wireless HD) are looking into this issue.
It was remarked that wireless desktop is an important topic, but industry is looking for other ways of doing it (e.g. JPEG-XR) and it should be avoided to use many different ways of doing it.
Another opinion expressed was that most probably, HEVC will face the necessity to encode mixed content. Therefore the design should take care of this.
A further opinion expressed was that if specific tools would be designed for this, they should be absolutely light-weight and potentially be switched on the profile level. Delay may also be an issue. Scalability may be important.
It was agreed to establish AHG to further study the subject and applications.
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