Dolby Laboratories Licensing Corporation

Tsung-Wei Huang

Guan-Ming Su

Harshad Kadu

Neeraj J Gadgil

Tao Chen

In an encoder, a high-dynamic range (HDR) image is encoded using a family of local forward reshaping functions selected according to an array of forward mapping indices (FMI) indicating which local forward reshaping function needs to be used for each pixel in the HDR image to generate a reshaped standard dynamic range (SDR) image. A decoder, given the reshaped SDR image, iteratively generates a reconstructed HDR image and estimated reshaped SDR images by adjusting a local FMI array and a local array of backward mapping indices (BMI) until an error metric related to the difference between the local BMI and FMI arrays and the difference between the estimate SDR images and the reshaped SDR image satisfy a convergence criterion. Techniques for generating families of local forward reshaping functions and local backward reshaping functions based on a global forward reshaping function are also presented.

Blind local reshaping in HDR imaging

Guided filtering is applied, with a camera raw image as a guidance image, to a first image to generate an intermediate image. A dynamic range mapping is performed on the intermediate image to generate a second image of a different dynamic range. The second image is used to generate specific local reshaping function index values for selecting specific local reshaping functions. The specific local reshaping functions are applied to the second image to generate a locally reshaped image.

Generating HDR image from corresponding camera raw and SDR images

Novel methods and systems for processing a single-layer backward compatible codec with multiple-channel multiple regression coefficients either provided in or pointed to in metadata such that the coefficients have been biased to prevent a shift in neutral colors. Pseudo neutral color patches are used along with a saturation weighting factor to bias the coefficients.

Neutral color preservation for single-layer backward compatible codec

A global index value is generated for selecting a global reshaping function for an input image of a relatively low dynamic range using luma codewords in the input image. Image filtering is applied to the input image to generate a filtered image. The filtered values of the filtered image provide a measure of local brightness levels in the input image. Local index values are generated for selecting specific local reshaping functions for the input image using the global index value and the filtered values of the filtered image. A reshaped image of a relatively high dynamic range is generated by reshaping the input image with the specific local reshaping functions selected using the local index values.

Adaptive local reshaping for SDR-to-HDR up-conversion

In a cloud-based system for encoding high dynamic range (HDR) video, each node receives a video segment and bumper frames. Each segment is subdivided into primary scenes and secondary scenes to derive scene-based forward reshaping functions that minimize the amount of reshaping-related metadata when coding the video segment, while maintaining temporal continuity among scenes processed by multiple nodes. Methods to generate scene-based forward and backward reshaping functions to optimize video coding and improve the coding efficiency of reshaping-related metadata are also examined.

Recursive segment to scene segmentation for cloud-based coding of HDR video

Methods and systems to detect and blend a surround area to avoid filtering artifact due to the area in image filtering are disclosed. The described methods include a compensation step and can be applied to arbitrary images with padded areas of arbitrary shape, such as letterboxes, pillar-boxes, ovals, or other shapes, including logos and close captions. Such methods detect the surround areas in the image with possible compression artifact and noise, and then perform blending to minimize the effects of the surround areas for any arbitrary image filtering operations.

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Sunnyvale, CA, United States of America

Tsung-Wei Huang