Sample adaptive offset control
Offset values, such as Sample Adaptive Offset (SAO) values in video coding standards such as the High Efficiency Video Coding standard (HEVC), may be improved by performing calculations and operations that improve the preciseness of these values without materially affecting the signal overhead needed to transmit the more precise values. Such calculations and operations may include applying a quantization factor to a video sample and at least some of its neighbors, comparing the quantized values, and classifying the video sample as a minimum, maximum, or one of various types of edges based on the comparison. Other sample range, offset mode, and/or offset precision parameters may be calculated and transmitted with metadata to improve the precision of offset values.
1. A decoding method, the method comprising:
receiving, by a decoder, a quantization factor, a value of coded video data at a first location of a frame, coded values of at least two locations each neighboring the first location;
decoding the coded video data at the first location, the decoding including scaling intermediate decoded video at the first location by the quantization factor;
evaluating, by the decoder, the value at the first location and the values at the neighboring locations;
classifying the decoded value of video data at the first location into a category based on the evaluation;
deriving an offset value based on the classification; and
performing sample adaptive offset filtering of the decoded video data at the first location according to the derived offset value.