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TELE-audiovision International — The World‘s Leading Digital TV Industry Publication

— 1 -12/2014


New Standard

AVS2 is a third generation cod-

ing standard under development

by the Audio Video Coding Stand-

ard Workgroup of China. It will

be a successor of AVS. The AVS

standard is comparable in per-

formance with the H.264/MPEG-4

AVC commonly used all over the

world for coding HD video. The

tests showed that both stand-

ards achieved almost identical

performance for HD signals. Per-

formance is here understood as

the PSNR (Peak Signal-to-Noise

Ratio). Only for smaller resolu-

tions (SD), MPEG-4 proved to be

a little better. An important fea-

ture of the AVS standard is its

lower complexity of the encoder

and decoder what makes it more


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 organiza-

tions. 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 Chi-

nese 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, re-

quires good background in mathemat-

ics and only a narrow group of experts

really can fully understand that. But

what we can understand are at least

the basic concepts underlying the

methods used in AVS2.

Let’s start with the texture analysis

and synthesis. The readers more fa-

miliar with computer games certainly

understand that their software games

synthesize various textures on differ-

ent 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 trans-

ferring information of many pixels of

a wavy sea or a distant flowerbed the

AVS2 encoder will analyze what tex-

ture is needed for this part of the pic-

ture 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


Another interesting method is super-

resolution based video coding. To put

it simply, a high resolution image is

reconstructed from multiple sequen-

tial low resolution images. During this

process high frequency modeling as

well as spacial-temporal interpolation

is performed. Interpolation means re-

constructing correct values for an un-

known image pixel located between

known pixels. Located either in space

(left/right/top/bottom) or time (previ-


Learning based video coding is may-

be even more interesting. The encoder

analyzes the video sequence in which

one or more objects are moving. It

yields information about size, loca-

tion 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 contain-

ing 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 Trans-

form (ABT), Directional transform, Ad-

vanced motion vector prediction and

Rate Distortion Optimization Quantiza-

tion (RDOQ).

We can say that up to the second

generation (AVS and MPEG-4) video

coding standards relied mainly on tak-

ing advantage of various imperfec-

tion 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 resem-

bling 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 real-

ity 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 compres-

sion ratio improvement over AVS as

HVEC has demonstrated over MPEG-

4? Can it save up to 50% of the band-

width? 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.

How to artificially

re-create a HD video

Jacek Pawlowski