Master thesis: Data reduction with the AV1 video codec compared to H.265
This work in cooperation with ORF deals with the codec of the future for ORF TVthek. Currently, H.264 is also used here for 4K UHD transmissions. In order to save both costs and transmitted data, the successor H.265 is evaluated in the context of the work and compared with the AV1 codec for use in the TVthek.
Nowadays, video compression is an important part of the internet. In order to reduce data, lossy video compression has become the standard. There are different methods of the types of video coding.
The H.264 AVC codec was first published in 2003 and gained over 80 percent market share in 2018 which makes it the most widely used video codec on the internet. Its successor H.265 HEVC as well as its competitor AOMedia V1 (AV1) allow even more data savings while maintaining the visual quality.
This thesis takes a look at the new video codecs AV1 and H.265 HEVC. While there are major differences in accessibility and licensing, both share the same core functions of coding. However, their implementation varies as both use different means and methods to save data. The ever-growing demand for video streaming platforms makes coding efficiency and the resulting data reduction key criteria for the industry.
These means and methods as well as the core coding functions of AV1 and H.265 will be explained at the beginning of this paper. Furthermore, industry-standards for technical measurements of the perceptual quality will be explained alongside their method of operation. The conclusions of the technical measurements with varying coding parameters and bit rates will be the foundation of the technical and subjective comparisons.
For these technical and subjective comparisons, three 4K Ultra HD videos with bit rates ranging from 2 to 8 Mb/s and 2-pass encoding are used. In the technical measurements (VMAF, PSNR, and SSIM) AV1 always outperforms the equivalent of H.265.
15 people participated in subjective testing to assess the quality of the codec videos compared to their original. While AV1 offers better performance than H.265 at low bit rates, the differences between these two are not conclusive at medium or high bit rates.
With slow camera pans (video 1) AV1 manages to have similar results across all bit rates whereas H.265 improves steadily outperforming AV1 at some point. When it comes to fast camera movements (video 2) AV1 has a far better subjective quality with results almost always twice as high as H.265. For fast pace cuts (video 3), AV1 achieves a better subjective quality than H.265 while using lower bitrates. It is only at the highest bitrate that H.265 outperforms the AV1 equivalent while both are interestingly worse than the second-highest bit rate of AV1.
AV1 surpasses H.265 at low bit rates. While H.265 sometimes offers a higher visual quality, AV1 uses less data while maintaining the same quality or even achieving a better one. Due to being open source and license-free, AV1 has advantages beyond visual quality. With future codecs like H.266 (VCC) at the starting position, AV1 will still be challenged in the future. Nevertheless, the widespread use of AV1 also depends on the compatibility and adaptation of industry giants.
February 2020 – January 2021
Supervisor: Dipl.-Ing. (FH) Matthias Husinsky
Second supervisor: Dipl.-Ing. (FH) Mario Zeller