Phase B recruits content-aware encoding to cut UHD bandwidth

As expected, this year’s NAB has been a UHD centric event, preparing broadcasters for delivery of major upcoming events, namely the 2018 World Cup and Tokyo 2020 Olympics, in what will be a make or break couple of years for many broadcasters and indeed the future of the UHD format, which has promised so much, yet driving bodies have struggled to ignite engagement.

In the same week the Ultra HD Forum rolled out its Phase B guidelines for UHD and HDR formats, US security firm Verimatrix scooped up a major contract upgrade at Taiwan’s Chunghwa Telecom for UHD content, while encoding expert Harmonic nailed a UHD deployment in Japan.

To UHD Phase B first of all, laying out guidelines for six essential areas for the development of UHD and HDR formats, selected on the basis that at least two services providers, or one major provider, have demonstrated interest in the technologies. The 80-page report covers content-aware encoding, dual-layer HDR technologies, high frame rate (100/120fps), dynamic HDR metadata systems, AVS2 video codec (pending public availability of the English language spec), and next-generation audio including Dolby AC-4 Audio and MPEG-H Audio.

An important Phase B building block is describing two dynamic metadata systems for HDR, with both Dolby Vision and SL-HDR1, whereas Phase A described use of Hybrid Log Gamma (HLG), the ten-bit variant of Perceptual Quantizer (PQ10) and HDR10, for which the guidelines were made commercially available in 2016. By upgrading to Dolby Vision, the Ultra HD Forum says the guidelines can use dynamic HDR metadata to create, distribute and render HDR content, plus preserve artistic intent across a wide variety of distribution systems and displays.

Here the Ultra HD Forum has rolled in Technicolor’s SL-HDR1 single-layer system, an incremental step to adding HDR, once broadcasters have their basic ATSC 3.0 signals up and running. SL-HDR1 allows broadcasters to simultaneously deliver a signal which can be rendered as SDR and HDR. In short, the bitstream is SDR but contains an extra packet which allows for HDR reconstruction, also known as a method of down-conversion. For example, in a compressed bitstream the metadata is called an SEI (supplemental enhancement information) message, so the SDR and HDR metadata is encapsulated within a video bitstream, meaning devices which do not view HDR can ignore the message, while devices supporting SL-HDR1, such as some LG TV sets, can read, decode and reconstruct HDR pictures. The graphic below, provided by the Ultra HD Forum, demonstrates the process in action.

Naturally, these formats will hike bandwidth to unprecedented levels. The Ultra HD Forum has outlined how HDR results in around 20% bandwidth increase, rising to a 25% increase for 60fps (standard frame rate) and 50% for 120fps (high frame rate), spiking all the way to a 300% bandwidth increase for full 4K UHD TV.

This brings us to a critical part of Phase B, introducing content aware encoding, otherwise known as content adaptive encoding (CAE), a class of techniques for improving coding efficiency, exploiting properties of the content to reduce bitrate. For example, content with little motion and static images is encoded using few bits, while content with high-motion scenes is encoded using the necessary bits for quality reproduction. The Ultra HD Forum stresses that “simple” content is prevalent, meaning content adaptive encoding can result in significant bandwidth savings.

Netflix is renowned for its R&D in CAE in partnership with the University of Southern California, the University of Nantes and University of Texas in Austin, complementing H.264 and H.265 codecs by applying content aware compression algorithms and reporting 20% bitrate savings per title in its entire catalog. Israeli compression company Beamr is also respected for its work in the adaptive encoding space.

The compression element is one of many reasons the take up of UHD and HDR formats by broadcasters and TV manufacturers has not fulfilled its potential, so taking a leaf from the Netflix book of encoding looks a solid move. While industry players get to work testing Phase B guidelines, the Ultra HD Forum is wary not to disrupt all the work which has gone into Phase A.

Not to be confused with the UHD Alliance, which handles CPE, content and the camera ends, the Ultra HD Forum is responsible for orchestrating standards development and deployment within the infrastructure.

Madeleine Noland, Chair of the Guidelines Work group said: “Our guidelines are regularly updated, and further technologies will be addressed. Also, as with the Phase A guidelines, we remain strongly focused on backwards compatibility so that the introduction of new solutions doesn’t break what’s already in place. Phase B guidelines will soon include end-to-end workflows for all distribution systems including OTA, MVPD and OTT, which is a hallmark of the Forum’s work.”

Moving on now to where a handful of instrumental vendors are making UHD moves at NAB. Taiwanese operator Chunghwa Telecom has been a Verimatrix customer for six years, this week upgrading its multimedia on-demand offering to include 4K UHD streaming and deploying the Verimatrix Video Content Authority System (VCAS) Ultra to secure its new premium content.

Ultra is the upgraded version of VCAS taking on board UHD services and advanced hybrid networks deployments, geared towards the transition to IP and software-based delivery and supporting cloud integrations. VCAS Ultra features multi-network Video-Mark watermarking technology, trusted execution environment support, and meets the MovieLabs’ defined UHD service requirements. However, the upgrade does not appear to include the ViewRight Ultra white label video services app, a component of VCAS Ultra which integrates the downloadable DRM ViewRight Web, Secure Player SDK for cross platform HLS and DASH stream playback, VideoMark watermarking, and Verspective client for monitoring performance.

Chunghwa Telecom’s multimedia on-demand service has 1.5 million subscribers. Taiwan’s largest telco also has over 10.5 million mobile subscribers, 10.7 million fixed line customers and 4.5 million broadband accesses.

UHD momentum is clearly with Asia Pacific, as Harmonic landed a small but respectable deal at NAB with QVC Japan, a TV shopping company founded in 1986 by Comcast and Liberty Media. Harmonic is supplying QVC Japan with its Spectrum X advanced media server for enabling UHD workflows, including support for HDR pass-through, featuring 14 ingest channels and 45 playout channels – for live and file-based production of UHD broadcasts.

Japanese TV households will be fully UHD by 2025, according to Masayuki Suga, deputy director, Ministry of Internal Affairs and Communications.

Harmonic is a founding member of the Ultra HD Forum, along with Comcast, Dolby, Ericsson, LG, NeuLion and Sony.