Update of variables, dynamic HDR and more in 2018


Earlier this week, the HDMI forum, the industry's open consortium to develop the HDMI specification, officially finalized and released the HDMI 2.1 specification. Previously announced in January, HDMI 2.1 is a combination and transport function update that introduces and expands several bits of functionality, but also allows higher resolutions and refresh rates thanks to a new 48 Gbps cable and badociated signaling.

The big news here is, of course, on the front of the resolution, where HDMI provides a resolution and refresh rate support of up to colossal 10240 x 4320 pixels, or what the HDMI forum refers to as "10K" , at 120Hz. Less eye-catching, but arguably more important is the support for dynamic HDR, updating of variables and improved Audio Return Channel (eARC) functionality. The HDMI forum is also introducing new features aimed at improving the refresh rates and low latency. The official release of the specification brings HDMI 2.1 a significant step to power and connect commercial devices.

The previously announced HDMI 2.1 specification remains in line with current trends in monitor and display technology: increasing resolutions to faster update rates, variable update rate and high dynamic range (HDR) functionality, everyone needs more and more data bandwidth. At the same time, HDMI 2.1 offers many new features over its predecessors, including over the current generation cables, one of which is the dynamic HDR, where the HDR metadata is much granular and can describe images frame by frame. This allows for higher quality through adjustments of contrast, brightness, detail and more per scene or frame, something that is not possible for static HDR because their same metadata are applied essentially to all scenes and frames of the title.

The new HDMI 2.1 standard also canonizes the variable update to an official HDMI standard. This has grown from the previous efforts of AMD in the field, where the company added FreeSync vaivable refresh to HDMI as a proprietary extension. As we have seen in FreeSync and G-Sync in recent years, the variable update technology eliminates tearing and greatly reduces stuttering, allowing for a more fluid game. The addition of variable update to the official HDMI standard means that the benefits of technology can now be brought to a much wider range of products and content.

For eARC, the technology itself allows televisions to send audio to a receiver or sound bar on the only HDMI connection cable. The ARC functionality is not new to HDMI, but the previous version was essentially limited to DVD quality audio, as there was not enough bandwidth for newer audio standards with lossless audio or more channels. Along with enhanced auto-discovery, eARC specifies much more channel bandwidth (~ 37 Mbps), allowing support for high-bit rate audio formats including DTS Master and Dolby TrueHD, object-based audio including DTS: X and Dolby Atmos , uncompressed 5.1 and 7.1, and 32-channel uncompressed audio.

In real world terms, this allows HDMI to work better without a dedicated audio receiver. Instead of routing the entire video + adio stream of 18 Gbps through a receiver, and all the problems that arise when having a device in the chain between a source and a television, the television can be the center of a system of home entertainment. audio through HDMI to a relatively simple sound bar or similar device. In other words, HDMI focuses on television instead of focusing on the receiver. Along with new eARC device discovery and control capabilities, applications, consoles, set-top boxes, Blu-ray players and other multimedia devices can be connected directly to a TV and controlled more easily with a single TV remote control.

However, a lot still depends on the device manufacturers. eARC can run some current cables and some manufacturers will provide firmware updates to add eARC to current products. However, this varies by product, and not all products can (or will be) updated to support eARC. As a result, the eARC standard will also be retrocompatible, but only to the extent that it can resort to ARC.

With all the bandwidth consumed by these functions, the HDMI Forum continues with its 48 Gbps high-speed HDMI cable, with its own logo and color requirements not yet published. Previously known as the 48G cable, it is still backward compatible with previous HDMI standards, features low EMI emission and comes with the flavors of existing Type A, C and D connectors. While the specification does not describe the length of the cable, the HDMI License considers 2 to 3 meters as the maximum length for pbadive cables. In addition to pbadive cables, the specification allows category 3 cables, badets and cable converters.

The HDMI forum expects UHS cables to be available in the first half of 2018, bearing in mind that these cables can only be shipped after complying with the HDMI 2.1 conformance test specification not yet published. These cables will be necessary to enable the full functionality of HDMI 2.1, particularly any feature that requires more bandwidth, such as the 4K120 and 8K60 display modes. Chroma and bit depth considerations are also required to determine what kind of cable is required; HDMI 2.1 supports the latest color spaces such as BT.2020 (Rec. 2020) with 10, 12 and 16 bits per color, with higher bit depths that quickly consume the cable bandwidth.

Otherwise, there is some good news on the front of the cable when it comes to eARC. The new audio channel standard does not require the UHS cable, but instead works on any cable with an Ethernet channel. This means that Standard, High Speed, Premium High Speed ​​and UHS cables may be compatible with the eARC. However, not all cables (especially older ones) support the Ethernet channel, since it has not been a requirement.

Speaking of cable bandwidth, since even 48 Gbps is not enough bandwidth for some of the resolutions and refresh rates that HDMI 2.1 claims to enable, the standard also includes support for compression Link VESA DSC 1.2a. This is necessary to support some resolution modes from 5K, where the bandwidth requirements would vary from 50 to 120 Gbps of uncompressed data.

Returning to yesterday's announcement, the HDMI forum also describes some improvements to the refresh rate to join the variable update: Fast Media Switching (QMS) and Fast Frame Transport (QFT). The first focuses on videos and movies, which allows source devices to change the resolution or frame rate of content instantly. The idea is to mitigate possible delays and interruptions when switching between media with different resolutions, update frequencies or television viewing modes. In most current products, the switching of the source signal causes stuttering or momentary shielding of the screen, which while harmless is a distraction and has led to bad decisions by manufacturers in the name of fluid interactions (eg, AppleTV HDR) , QMS is a more appropriate solution to the problem.

Regarding QFT, the HDMI forum described the function as allowing video frames to be transmitted faster from the source without increasing the source frame rate. In turn, this aims to reduce the latency and tearing of the screen in the game and interactive virtual reality in real time, although the HDMI forum also points to a more receptive karaoke as another use case. While these capabilities can be combined, the HDMI forum reiterates that the HDMI 2.1 feature set depends on the manufacturer's implementations, and that features must be enabled both at the source and on the screen.

Along with these refresh rate features is the new Automatic Low Latency Mode (ALLM), which uses what is described as automatic latency mode switching of applications such as movies and videos to low latency applications, for example games and virtual reality. In other words, ALLM seeks to optimize the latency configuration for a wide range of applications and to recognize especially those sensitive to latency. The details were very scarce, but the given description seems to imply some inconvenience or cost not mentioned, since otherwise the low latency configuration would be enabled at all times.

In terms of other features, the details are vague, which is typical of these types of industry standard closed specifications. And while full-featured HDMI 2.1 products will not be available for some time. The HDMI 2.1 Compliance Test Specification is still in development and will be published in stages during the first three quarters of 2018. Since today's version marks a delay from the originally planned Q2 2017 window, it may be until mid-2019 before that consumers are able to take advantage of what HDMI 2.1 has to offer, if manufacturers provide them.

Taken together, the HDMI 2.1 specification has many additional features that complement each other: variable update and improved refresh rate capability on smart TVs and consoles may allow higher resolutions than another mode could not be played or not seen The broad HDR provides a broad incentive to get more HDR content, and even with all modern multimedia devices in the digital living room, the eARC can make such a design (high-end audio included) ) is really manageable. All these features are made with cables compatible with previous versions designed to easily coexist with the current ecosystem. But none of these is mandatory and depends largely on the implementation, so it is up to the manufacturers to work with all the options and translate them into products that are accessible and applicable to the consumer. The other side of the coin is that these non-mandatory features are likely to be the most useful for consumers; outside of very specific industrial, medical or commercial uses, resolutions of 8K and beyond are not very practical at this time due to lack of content.

For more information, the HDMI forum has a public slide panel while HDMI Licensing Administrator has a Frequently Asked Questions on HDMI 2.1 available. The full specification can be accessed on the Adopter Extranet.

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