Perceptually Optimized Bit-Allocation and Associated Distortion Measure for Block-Based Image or Video Coding

It is well known that input-invariant quantization in perceptual image or video coding often leads to visually suboptimal results and that quantization parameter adaptation (QPA) based on a model of the human visual system can improve subjective coding quality. This paper introduces a simple low-com...

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Bibliographic Details
Main Authors: Helmrich, Christian R., Bosse, Sebastian, Siekmann, Mischa, Schwarz, Heiko, Marpe, Detlev, Wiegand, Thomas
Format: Conference Proceeding
Language:English
Subjects:
Bit allocation
Distortion
Distortion measurement
human perception
psychovision
quality metrics
Quantization (signal)
Video coding
Visualization
Weight measurement
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Summary:It is well known that input-invariant quantization in perceptual image or video coding often leads to visually suboptimal results and that quantization parameter adaptation (QPA) based on a model of the human visual system can improve subjective coding quality. This paper introduces a simple low-complexity QPA algorithm, controlled using a block-wise perceptually weighted distortion measure representing a generalization of the PSNR metric. The weighting scheme of this WPSNR metric is based on a psychovisual model. It directly leads to a perceptually adapted scaling of the block-wise Lagrange parameter used in the bit-allocation process in the encoder and, consequently, to a block-wise QPA. Unlike prior QPA approaches, the proposal avoids classifications of picture regions and easily extends from still-image or grayscale to video or chromatic coding. The WPSNR metric also uses fewer algorithmic operations than e. g. the multiscale structural similarity measure (MS-SSIM). Due to the results of two formal subjective tests indicating its visual benefit, the QPA proposal has been adopted into VTM, the currently developed Versatile Video Coding (VVC) reference software.
ISSN:2375-0359
DOI:10.1109/DCC.2019.00025