Abstract

In past years, several visual saliency algorithms have been proposed to extract salient regions from multimedia content in view of practical applications. Entropy is one of the important measures to extract salient regions, as these regions have high randomness and attract more visual attention. In the context of perceptual video coding (PVC), computational visual saliency models that utilize the charactertistics of the human visual system to improve the compression ratio are of paramount importance. To date, only a few PVC schemes have been reported that use the visual saliency model. In this paper, we conduct the first attempt to utilize entropy based visual saliency models within the high efficiency video coding (HEVC) framework. The visual saliency map generated for each input video frame is optimally thresholded to generate a binary saliency mask. The proposed HEVC compliant PVC scheme adjusts the quantization parameter according to visual saliency relevance at the coding tree unit (CTU) level. Efficient CTU level rate control is achieved by allocating bits to salient and non-salient CTUs by adjusting the quantization parameter values according to their perceptual weighted map. The attention based on information maximization has shown the best performance on newly created ground truth dataset, which is then incorporated in a HEVC framework. An average bitrate reduction of is achieved by the proposed HEVC compliant PVC scheme with the same perceptual quality and a nominal increase in coding complexity of when compared with HEVC reference software. Moreover, the proposed PVC scheme performs better than other HEVC based PVC schemes when encoded at low data rates.

Highlights

  • The majority of information being communicated and shared on the Internet is in the form of multimedia

  • Images and videos captured from imaging and handheld devices possess an enormous amount of redundant information, which needs to be exploited for efficient transmission and storage

  • Video content has a high impact on encoder performance, test video sequences for high efficiency video coding (HEVC) are defined according to resolution, application domain and genre [1]

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Summary

Introduction

The majority of information being communicated and shared on the Internet is in the form of multimedia. Images and videos captured from imaging and handheld devices possess an enormous amount of redundant information, which needs to be exploited for efficient transmission and storage. Image and video coding techniques are developed with the aim to remove redundant information to reduce size, while preserving visual quality. Telecommunication Union (ITU) and the International Standards Organization (ISO) have developed a series of video coding standards over the last three decades. In 2010, the ITU video coding experts’. Group (VCEG) and the ISO motion picture experts’ group (MPEG) created a joint collaborative team on video coding (JCT-VC) for the development of high efficiency video coding (HEVC), with the aim of achieving high compression gain [1]. Since the first draft of HEVC in April 2013, the research community has contributed to improving the performance of HEVC and its implementation on Entropy 2019, 21, 964; doi:10.3390/e21100964 www.mdpi.com/journal/entropy

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