Kvazaar 2.0: Fast and efficient open-source HEVC inter encoder

High Efficiency Video Coding (HEVC) is the key to economic video transmission and storage in the current multimedia applications but tackling its inherent computational complexity requires powerful video codec implementations. This paper presents Kvazaar 2.0 HEVC encoder that is the new release of our academic open-source software (github.com/ultravideo/kvazaar). Kvazaar 2.0 introduces novel inter coding functionality that is built on advanced rate-distortion optimization (RDO) scheme and speeded up with several early termination mechanisms, SIMD-optimized coding tools, and parallelization strategies. Our experimental results show that the proposed coding scheme makes Kvazaar 125 times as fast as the HEVC reference software HM on the Intel Xeon E5-2699 v4 22-core processor at the additional coding cost of only 2.4% on average. In constant quantization parameter (QP) coding, Kvazaar is also 3 times as fast as the respective preset of the well-known practical x265 HEVC encoder and is still able to attain 10.7% lower average bit rate than x265 for the same objective visual quality. These results indicate that Kvazaar has become one of the leading open-source HEVC encoders in practical high-efficiency video coding.