UHD Calls for New TV Infrastructure

To deliver UHD performance, service providers must develop and deploy a new generation of set-top boxes and other equipment that take advantage of a new set of standards.

by Wade Wan

MANUFACTURERS are hoping that the promise of a dramatic new immersive TV viewing experience will compel consumers to invest in ultra-high-definition (UHD) TV.  Also known as 4K TV, UHD is already being embraced by major content producers in both film and television.  In 2013 alone, the number of movies filmed in 4K resolution increased five-fold from 10 to 50.  The infrastructure for filming in this format is nearly complete, so finding a way to deliver this next-generation content to home viewers is the next big hurdle (Fig. 1).

Fig. 1: High definition provided 6× the resolution of standard definition; now UHD offers 4 × the resolution of high definition.

Content providers in particular will need ways to deliver premium content at higher resolutions than are possible with current delivery methods – all while providing seamless quality of service to subscribers.  To find a solution to this dilemma, multiple players in the industry have collaborated to develop the new standards necessary to enable cable, satellite, and OTT (Over the Top, meaning via the Internet) providers to efficiently and cost effectively deploy UHD TV offerings in the near term.  Those efforts are already yielding promising results.

UHD is supported via a more efficient video-compression standard, High-Efficiency Video Coding (HEVC), which was ratified in January 2013.  The transition to HEVC marks a major shift in the industry.

The Coming Change in Technical Specs

HDTV offers 8-bit resolution of 1920 × 1080 pixels in an interlaced format of 60 fields/sec, which can be delivered at a bit rate of about 6 Mbits/sec (Mbps) using the current AVC compression standard.  UHD TV, on the other hand, will deliver a 10-bit resolution of 3840 × 2160 pixels in a progressive format of 60 frames/sec.  This would require about 30 Mbps if the current AVC compression standard is used, which would be quite significant and costly, but use of the HEVC compression standard can lower the bit rate to about 15 Mbps, making it more realizable for cost-efficient implementation and deployment (Table 1). 

---

Parameter	HDTV Format	UHD TV Format
Spatial Resolution (pixels/frame)	1920 × 1080	3840 × 2160
Pixel Depth (bits/pixel)	8	10
Frame Rate (frames/sec)	30	60
Uncompressed Pixel Rate (Mbits/sec)	497.664	4,976.640

Given the exponential increase in size and bandwidth required to deliver uninterrupted 4K 60-frame/sec transmissions, the HEVC standard significantly speeds the transmission of 4K content, allowing operators and users to receive UHD content in half the time or at 50% of the bit rate compared to the current AVC coding standard.

UHD displays that are fully compliant with the new standards will also offer an exponentially greater array of colors (color gamut).  The UHD color-gamut standard, BT.2020, replaces the BT.709 gamut standard previously used for HDTV.  Because BT.2020 can display more colors, it requires a larger bit depth than BT.709 to properly represent all the possible colors in this wider color gamut.  Thus, the 10- and 12-bit coding of BT.2020 will replace the 8- and 10-bit coding of BT.709.

The changes in technical specifications of UHD TV versus HDTV systems even reach down to the specs for the HDMI port, which affect both transmitters like STBs and receivers like display devices.  The present HDMI 1.4 interface standard does support UHD, but in a very limited fashion, offering support only when the pixel data standard is no more than 8 bit, the frame rate is no more than 30 frames/sec, and the maximum throughput is no more than 10.2 Gbits/sec (Gbps).  To overcome those limitations, a new HDMI 2.0 standard was developed that increases the bandwidth supported across the HDMI interface to 18 Gbps. The new specification can then support UHD resolutions at 50 or 60 Hz over a single interface, which potentially avoids the hassle of needing multiple cables and connectors to handle the increased throughput of UHD services.  Without HDMI 2.0, video would need to be cut into separate sections before the HDMI transmitter, then run separately through multiple HDMI links and assembled back together correctly with care to ensure every section came from the same picture.

Another crucial technical requirement for UHD services is content protection.  High-Bandwidth Digital Content Protection (HDCP) is a digital copy protection and digital rights management specification for securing audiovisual content between devices.  HDCP version 2.2 for mapping to the HDMI interface was established in February 2013.  Securing the HDMI digital interface with HDCP 2.2 is regarded as the minimum requirement for securing the transmission of UHD content in order to satisfy the distribution requirements of content providers.

As a system-on-chip (SoC) developer, Broadcom has been one of the most influential companies in the development of the HEVC/H.265 standard and has launched a broad portfolio of HEVC-enabled chipsets that are available for the full range of cable, satellite, and broadcast providers to expand current HD offerings and launch UHD content to subscribers.

Broadcom anticipates healthy adoption of HEVC/H.265 and has publicly engaged with leading encoder vendors, operators, and partners to ensure this codec’s success in the marketplace, whether that be through tech-nology demonstrations or new service offerings to subscribers around the world in 2014.

We believe that HEVC enables consumer-electronics manufacturers and service providers to bring faster video delivery to subscribers over consumer devices thanks to higher compression rates.  The compression standard also allows service providers to provide both higher-quality streaming media services at a lower bit rate and the same or even more content at an equivalent bit rate.  In the end, service providers can choose how to capitalize on this increased efficiency, from putting more channels on the same bandwidth to delivering similar quality video at half the bit rate or delivering better services using the same bit rate.

Potential Hurdles: Interoperability and Interlaced Content

One key technical hurdle for UHD may be the time it takes for the ecosystem to develop; more specifically, the interoperability between different implementations.  This is not a problem with how standards are specified, but rather reflects the fact that advanced technologies and specs do not immediately interoperate when a specification is published.  However, this begins a whole new phase in which true industry interoperability can be proved as devices are actually tested among different vendors.  As a key provider of these technologies, Broadcom has made considerable efforts in areas such as HEVC and HDMI interoperability, and one can easily see that much progress has been made since these standards were first published.

The coding of interlaced content is a heavily debated issue for HEVC as well.  In fact, there was initial confusion in the market that HEVC could not support interlaced formats, which is incorrect.  That said, critics still debate today whether interlaced content is as well supported in HEVC as it is in AVC, despite such support being a conscious decision of the HEVC standardization committee during evaluation.

Further UHD Support Is Needed

UHD has already spurred the introduction of new displays and set-top boxes and has been used to great effect in the production of films such as X-Men Origins: Wolverine, Night at the Museum, and World War Z, just to name a few.  And when it comes to sporting events, nothing delivers live action better than UHD, in part due to the frame rate and color depth incorporated into the new technology.  This year’s live UHD broadcasts of the Sochi Olympics and World Cup represented a significant proof point.  According to market information advisory firm DisplaySearch, the 2014 World Cup played a significant role in boosting adoption of UHD TVs.  In fact, analysts at Digitimes Research predict that UHD-TV panel shipments will have increased 475% by the end of 2014 alone.¹

In summary, UHD TV is poised to deliver a major new viewing experience to consumers with doubling of both the horizontal and vertical resolution available and a tenfold increase in the raw pixel data rate over HDTV.  But to deliver this superior performance, service providers must develop and deploy a new generation of set-top boxes and other equipment to meet the new industry standards for improved video compression, wider color gamut, HDMI interface, and content protection.

References

¹Digitimes Research; www.digitimes.com/news/a20140529PD216.html?chid=  •

---

Wade Wan is a Technical Director in the Broadband & Connectivity Group at Broadcom Corp.  His primary responsibility is to oversee the complete development cycle of video-compression technology in Broadcom’s system-on-chip (SoC) solutions, ranging from standardization to internal design and development to product deployment and support. The author can be contacted through tamaras@broadcom.com.