For a long time I have been thinking about using a small, low energy computer as a HTPC - a multimedia playback machine. A novelty inspired me to look again at what and how you can watch the PC in 4K resolution with HDR.

1. What can you watch on a PC in 4K with HDR?

Examples:

• 4K videos on YouTube or Vimeo - available for free (unfortunately, the range of available content is limited mainly to short demonstration films such as those displayed in showrooms and supermarkets to advertise TV sets);

• a film recorded by itself (many new smartphones and sports cameras record video in 4K resolution, although rarely in 60 fps);

• movies and TV series streamed in the Netflix service (to be able to watch 4K and HDR video, you have to pay the most expensive version of the service for PLN 52 a month, and I will tell you about other requirements);

• film na płycie Blu-ray UHD (niestety, napędy Blu-ray UHD do pecetów są jeszcze słabo dostępne). Wrócę do tej kwestii niebawem, kiedy będę dysponował odpowiednim napędem.

2. Technical Limitations

The device, which would play materials in 4K resolution and with HDR, must have the appropriate technical features. High-definition movies are mostly coded using one of two codecs: H.265 (HEVC) or VP9. The former is used, for example, in movies on Blu-ray UltraHD discs and in Netflix and Amazon Prime Video services. The latter is used by YouTube in movies with resolutions above 1920 × 1080 and liquidity above 30 fps. (lower resolutions are available in VP9 and H.264 formats, and higher - only in VP9).

Decoding VP9 or HEVC using a general purpose processor is expensive computationally and energetically, therefore hardware decoders are usually used in equipment adapted for 4K display. They have almost all modern smartphones, televisions and graphics cards of the latest generation. In the case of PCs, it is important not only whether the graphics card can hardware-decode a given format in the appropriate resolution and bit rate, but also whether the software can use this possibility. As I will show in a moment, there are a lot of software shortcomings.

3. Non - Technical Limitations

HDCP 2.2

One such limitation is the HDCP 2.2 (High-Bandwidth Digital Copy Protection) security system used in the overwhelming majority of commercial 4K movies. HDCP limits access to the data stream flowing from the source (the device that decompresses the video) to the display. Netflix, Amazon Prime Video, Blu-ray movies UHD - all these ways of distributing content to PCs require that the graphics card driver and display device are compatible with HDCP 2.2.

As I mentioned, the HDCP 2.2 requirement only results from contracts between film suppliers. There are exceptions to this: for example, movies from the Netflix service can be streamed in 4K from a PlayStation 4 (slim) console, although it only supports the previous HDCP security standard, 1.4. We guess that Sony's position in the negotiations and that PS4 is a closed, secured by other methods of the system, convinced Netflix and all who provide him with films that they are not threatened with an extreme scale of piracy.

The HDCP security system was developed by Digital Content Protection, the founder and owner of which is Intel. Manufacturers and sellers of HDCP-compliant equipment and content protected by HDCP must purchase a valid license from Digital Content Protection. One of the reasons why entertainment companies collectively use such security is the US DMCA law. On the one hand, it allows the users to dispose of the purchased cultural goods quite freely. On the other hand, it prohibits the distribution of devices and software that break security - you can only do it yourself and in secret. Even publishing information on the operation of security systems on the Internet can be treated as a violation of the intellectual property of security authors. The use of HDCP can therefore provide content providers with a very favorable position in lawsuits to breach copy protection.

Microsoft PlayReady 3.0

On Windows PCs, PlayReady 3.0 is also used (see Microsoft's documentation). This restricts access to said data stream before it goes under the control of HDCP security, and at the same time is to ensure that the HDCP 2.2 subsystem is not "controlled" by software to bypass security (e.g., a virtual machine). You could say that PlayReady is a link between content security on a Blu-ray disc or in an Internet stream and HDCP protection. PlayReady requires the appropriate version of Windows 10, a compatible GPU driver, and some way to provide an encrypted, cut-off enclave for video playback software: either Intel Software Guard Extensions (for Intel processors) or TrustZone (for AMD processors, probably also Qualcomma).

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