Abstract
AV1 is an open-source video coding technique developed by Alliance for Open Media (AOMedia). Many powerful coding tools introduced to AV1 has made its encoding time significantly increased. In this paper, we aim at simplifying the AV1 encoder by facilitating selection of some coding tools depending on users' specific application preference. We firstly design a coding tool OFF-test to evaluate coding performance of intra, inter, and in-loop filter coding tools in AV1 encoder in order to define a criterion to evaluate the importance of each coding tool by measuring the Bjøntegaard delta bit rate (BDBR) loss and time saving (TS) when each coding tool is turned OFF. Furthermore, the importance of each coding tool is analyzed based on the predefined criterion. Lastly, we suggest two intra coding tool selection methods, three inter coding tool selection methods, and three overall coding tool selection methods to simplify AV1 encoder based on users' preference of quality-priority or low-complexity-priority. Experimental results show that our proposed low-complexity-priority selection method saves 30.72% of encoding time with only 0.91% loss in BDBR sense, and the quality-priority selection method saves 4.64% of encoding time with 0.02% BDBR loss.
Highlights
A S DEMAND of high-quality video contents by users continues to grow fast, the development of more powerful video compression techniques becomes utmost important
From the results we can observe that the in-loop filter coding tools are very important to coding performance since turning OFF either constrained directional enhancement filter (CDEF) or restoration filter causes approximately more than 0.8% Bjøntegaard delta bit rate (BDBR) loss but saves very little time complexity especially under random access (RA) encoding configuration
The low-complexity priority selection achieves 30.72% of encoding time saving with less than 1% BDBR loss, and the moderate quality-complexity priority application suffers from 0.46% BDBR loss while saving 21.37% of encoding time
Summary
A S DEMAND of high-quality video contents by users continues to grow fast, the development of more powerful video compression techniques becomes utmost important. The authors in [7]–[17] investigated compression efficiency and encoding time complexity of different coding techniques under multiple coding configurations. It is always very desirable to design a fast encoder with only little coding performance loss In this context, many works [21]–[29] have focused on designing low complexity encoders irrespective of coding techniques. In [34] and [35], the authors evaluate the coding performance and time complexity of intra coding tools adopted in AV1 encoder. Since users can have many different encoding preferences based on their applications or usage scenarios, our target in this paper is to design a simplified AV1 encoder optimized for user’s different preference by selecting only necessary coding tools under certain user priority.
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