Rate Control Adaptation for High-Dynamic Range Images

摘要

A high dynamic range input video signal characterized by either a gamma-based or a perceptually-quantized (PQ) source electro-optical transfer function (EOTF) is to be compressed. Given a luminance range for an image-region in the input, for a gamma-coded input signal, a rate-control adaptation method in the encoder adjusts a region-based quantization parameter (QP) so that it increases in highlight regions and decreases in dark regions, otherwise, for a PQ-coded input, the region-based QP increases in the dark areas and decreases in the highlight areas.

主权项

1. A method for rate-control adaptation in an image encoder, the method comprising:
accessing by the encoder an input image to be compressed, the image comprising one or more image regions; determining by the encoder a threshold for the image;
for an image region in the image, using the encoder:computing a metric of luminance for pixels in the image region;determining a quantization parameter delta (QPdelta) for the image region based on the metric of luminance; andadjusting a base quantization parameter (QPBase) based on the quantization parameter delta and the threshold to generate a new quantization parameter (QPnew), wherein the new quantization parameter is smaller than the base quantization parameter if the metric of luminance is higher than the threshold, and the new quantization parameter is larger than the base quantization parameter if the metric of luminance is lower than the threshold.