Variance Adaptive Quantization and Adaptive Offset Selection in High Efficiency Video Coding

Video compression uses encoding to reduce the number of bits that are used for representing a video file in order to store and transmit it at a smaller size. A decoder reconstructs the received data into a representation of the original video. Video coding standards determines how the video compression should be conducted and one of the latest standards is High Efficiency Video Coding (HEVC). One technique that can be used in the encoder is variance adaptive quantization which improves the subjective quality in videos. The technique assigns lower quantization parameter values to parts of the frame with low variance to increase quality, and vice versa. Another part of the encoder is the sample adaptive offset filter, which reduces pixel errors caused by the compression. In this project, the variance adaptive quantization technique is implemented in the Ericsson research HEVC encoder c65. Its functionality is verified by subjective evaluation. It is investigated if the sample adaptive offset can exploit the adjusted quantization parameters values when reducing pixel errors to improve compression efficiency. A model for this purpose is developed and implemented in c65. Data indicates that the model can increase the error reduction in the sample adaptive offset. However, the difference in performance of the model compared to a reference encoder is not significant. effektivare komprimeringsmetod.