Shulou(Shulou.com)11/24 Report--

HDR is the abbreviation of High dynamic range (High Dynamic Range). Compared with SDR (Standard dynamic range, Standard Dynamic Range), HDR can display a wider luminance range, and the screen peak brightness can reach 10000 Nits. the display ability of highlight and dark areas is significantly improved compared with SDR, so it can display the picture content of both highlight and dark light areas at the same time, and the contrast, layering and transparency are stronger and more suitable for the real world than SDR. Therefore, the subjective quality experience of the audience will be greatly improved.

In recent years, with the progress and market promotion of HDR shooting and production, video codec, screen display and other technologies, a large number of terminal devices supporting HDR codec and rendering display are widely used, and the demand and frequency of users for HDR playback are increasing rapidly.

In order to meet the increasing demands of users for picture quality, Tencent Video introduced the Dolby Vision,2019 high-quality technology brand in 2017 and upgraded to "Color Vision" in 2020 to provide cinema-level HDR picture quality experience for users.

In the latest version released in June 2023, Tencent Video deeply optimized video SDR2HDR automatic reproduction technology, HDR Vivid dynamic metadata technology, optimal code control and playback adaptation, and significantly improved the picture brightness, contrast, clarity and color of HDR video.

Tencent Video is committed to continuously improving the sense of immersion and presence in video watching. Based on the faithful director's style and intention, Tencent Video's SDR2HDR automated reproduction technology optimizes inverse tone mapping, color enhancement, ROI intelligent protection, adaptive sharpness enhancement and other algorithms to achieve the most realistic light and shadow effects, light and shade contrast, hue and retina (real human eyes) level of particle clarity.

SDR2HDR automatic reproduction technology is a problem that needs to be weighed, not only to achieve a significant picture quality enhancement effect, but also to respect the creative intention of the original director (for example, some other similar products are oversaturated), which puts forward high requirements for the intelligence of the algorithm. Through the above optimization, Tencent Video's current algorithm has achieved a fairly good balance in all aspects and significantly improved the picture quality effect.

The mainstream distribution format standards of HDR are Dolby Vision, HDR10, HLG, HDR10 + and HDR Vivid. The differences in the main parameters of these standards are shown in the following table, of which the core difference is metadata:

Considering the openness of technology, the advanced nature of technology, the license fee and the degree of equipment support, Tencent Video chose HDR Vivid as the main distribution format of HDR video. HDR Vivid is a series of HDR standards independently developed by China and led by the World Ultra High definition Video Industry Alliance (UHD World Association, abbreviated as UWA). Its dynamic metadata scheme can not only solve the terminal rendering consistency problem of static metadata schemes such as HDR10, but also dynamically adjust the mapping algorithm according to the changes of video content, maximize the display ability of terminal devices and improve the rendering quality of rendered images.

Tencent Video, as an executive director and member of UWA, deeply participated in the whole process of standard formulation and ecological construction, becoming the first video platform to support HDR Vivid, self-developed HDR Vivid dynamic metadata content production technology, and supported frame-level dynamic light and shadow changes. compared with HDR10 using static metadata, it is more real and more restores the senses of the real world, as if watching movies at the shooting scene. At present, Tencent Video color video has been fully online in HDR Vivid format, covering movies, dramas, documentaries and other head boutique content.

Although it has high-quality video content, Tencent Video has a large number of users, users have different models, the models are seriously fragmented, and the equipment capabilities of the models are also quite different, which makes it quite difficult to popularize HDR. Some devices certified by UWA Alliance HDR Vivid are supported on hardware, such as Huawei Mate50,P50. This kind of device can play HDR Vivid using the same scheme as playing ordinary SDR video (MediaCodec decoding + SurfaceView rendering), giving full play to the hardware capabilities of the device without the need for software Tone Mapping processing. While more devices are not certified by the UWA Alliance, or have been on the market before the release of the UWA Alliance and HDR Vivid standards, such devices require additional adaptation. However, HDR Vivid has certain requirements for the performance of the equipment, especially for the display ability of the device screen, hardware decoder, system HDR interface and so on. How to distinguish the ability of the equipment and adopt an appropriate adaptation scheme is a difficult point for HDR Vivid to land in the terminal.

In the process of participating in the formulation of HDR Vivid standards, Tencent Video and other colleagues of the UWA Alliance continued to explore and research, under the professional guidance of the alliance experts to provide Tone Mapping algorithm implementation, after more than a year of iteration and optimization, combined with the current situation that Tencent Video users' terminal devices are widely distributed in four different HDR capability levels, explore a HDR Vivid terminal solution that is more in line with the needs of end users. And has been in Tencent Video full platform (iOS platform, Android platform, Windows platform, macOS platform) full online, and coverage of the vast majority of terminal equipment.

With the recent hit TV dramas such as "Yugu Yao", "Acacia" and "West out of Yumen" have provided users with a new version of HDR Vivid video experience online, our team is also following up users' image quality feedback at any time, continuously optimizing the algorithm and viewing experience.

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