Luma Range Scaling for Enhanced VVC Efficiency in Video Coding for Machines

Recent years have shown significant growth in video data traffic for machine vision applications, catalyzing new standardization efforts in video coding for machines (VCM). These activities focus on compressing images and videos for machine vision tasks, rather than for human viewing. In this work, we propose a novel method that scales down the luma range to enhance the coding efficiency of Versatile Video Coding (VVC) for machine consumption. This method results in a lower bitrate after encoding and has only minimal adverse effects on the accuracy of machine vision tasks. In our experiments, we down-scale the luma channel of the input video using luma-scaling factors from 0.2 to 0.9 and evaluate coding results with optional back-scaling to the original range before machine vision tasks. Our results with the VVC Test Model (VTM) demonstrate that the proposed technique achieves coding gain of up to 37.9 % and 46.1% for the same object detection and tracking accuracy, respectively.