FEATURE New Standard AVS2 A New Video Coding Standard •requires even less of the original video information •re-creates parts of the original video by artificial intelligence •saves on the amount of data required to transmit •makes use of software developed for gaming 94 TELE-audiovision International — The World‘s Leading Digital TV Industry Publication — 11-12/2014 — www.TELE-audiovision.com www.TELE-audiovision.com — 11-12/2014 — TELE-audiovision International — 全球发行量最大的数字电视杂志 95 FEATURE New Standard HD video How to artificially re-create a HD video Jacek Pawlowski AVS2 is a third generation coding standard under development by the Audio Video Coding Standard Workgroup of China. It will be a successor of AVS. The AVS standard is comparable in performance with the H.264/MPEG-4 AVC commonly used all over the world for coding HD video. The tests showed that both standards achieved almost identical performance for HD signals. Performance is here understood as the PSNR (Peak Signal-to-Noise Ratio). Only for smaller resolutions (SD), MPEG-4 proved to be a little better. An important feature of the AVS standard is its lower complexity of the encoder and decoder what makes it more practical. Another reason for China developing the AVS standard is saving money by not paying royalties for MPEG-4. Most of the patents in AVS standard belong to Chinese companies and organizations. They charge for them much less than the Western world companies do for MPEG-4. In this way, a Chinese consumer can save maybe 5-10% when buying a AVS receiver without MPEG-4 decoder. But China didn’t stop at AVS and developed the standard further one. AVS2 will have a better compression ratio and thanks to that it will be more adequate for ultra high definition TV. Actually, AVS2 can be seen at the Chinese answer to the new HEVC/H.265 standard published recently by ISO/ IEC and ITU. In what ways will AVS2 ensure better performance? Well, the very accurate explanation is extremely complex, requires good background in mathematics and only a narrow group of experts really can fully understand that. But what we can understand are at least the basic concepts underlying methods used in AVS2. the Let’s start with the texture analysis and synthesis. The readers more familiar with computer games certainly understand that their software games synthesize various textures on different objects required in a game. And there is no need to store every pixel of the surface. The software program can create complex texture knowing only a small pattern of a bigger area. New compression algorithms in AVS2 can also do that. And instead of transferring information of many pixels of a wavy sea or a distant flowerbed the AVS2 encoder will analyze what texture is needed for this part of the picture and will send to the receiver only this information (only a small picture). Now, the decoder in your receiver will fill in holes in an image by synthesizing non-repetitive parts of an image, as in inpainting. Another interesting method is superresolution based video coding. To put it simply, a high resolution image is reconstructed from multiple sequential low resolution images. During this process high frequency modeling as well as spacial-temporal interpolation is performed. Interpolation means reconstructing correct values for an unknown image pixel located between known pixels. Located either in space (left/right/top/bottom) or time (previous/next). Learning based video coding is maybe even more interesting. The encoder analyzes the video sequence in which one or more objects are moving. It yields information about size, location and motion of the objects. Using computer graphics methods, it creates models of each object. It sends to the receiver decoder information about the model and animation information. This is sufficient for low resolution vid- eo. To make it suitable for HD video, some additional information containing residual pixel signal is sent. This is simply the difference between the model and the real image processed by the encoder. Except for the above new concepts described above, there are also more improvements in the methods and algorithms used so far. So, AVS2 will take advantage of: Super-macroblock prediction, Adaptive Block-size Transform (ABT), Directional transform, Advanced motion vector prediction and Rate Distortion Optimization Quantization (RDOQ). We can say that up to the second generation (AVS and MPEG-4) video coding standards relied mainly on taking advantage of various imperfection of the human eye to achieve high compression ratio. AVS2 takes a step further. Some elements of the video will be in fact computer animations or computer generated textures resembling real things. This is another step away from transmitting the original video: what you see on your monitor is a brand new artificially created video, which looks as the original, but in reality it is re-created by using only some parts of the original video. Compressed video already went away from a 1:1 transmission, as in the old analog times (the original is identical to the copy). Now even less of the original is needed, to re-created it. Will AVS2 achieve similar compression ratio improvement over AVS as HVEC has demonstrated over MPEG4? Can it save up to 50% of the bandwidth? Some scientific papers report up to 37% of bandwidth reduction. This can change because the standard is not finalized yet and very few test results have been published. So let’s see where all this will eventually end. 96 TELE-audiovision International — The World‘s Leading Digital TV Industry Publication — 11-12/2014 — www.TELE-audiovision.com