Transitioning from a traditional AVC workflow may seem daunting for video providers streaming in multiple formats, but the move to HEVC will be cost-saving and result in consumer satisfaction, writes Anthonypillai Stanislous of Rohde & Schwarz.
Across the Middle East, broadcasters are planning their launch strategies for new HD, 4K and UHD services. Inevitably, this will have important implications on their infrastructure upgrade strategies. However, before you start thinking about major capex projects, it is important to look at the challenge in a broader perspective. How important could something as simple as your choice of video encoding codec be to system capacity and bandwidth requirements? Here, we explain how HEVC could be the ideal technology to help broadcasters make this key migration.
For more than a decade, H.264, also known as AVC, has been the go-to video compression standard. Whenever you download a movie, view HDTV broadcasts or watch cable TV, there’s a very good chance that the video stream has been encoded with H.264. However, many broadcasters in the Middle East are still using MPEG-2, a 20-year-old codec.
H.264 is a great compression standard for a number of reasons. It provides very good quality at relatively low bitrates, and its widespread use means it’s supported by essentially every video playback device made in the past five to ten years. It’s also very versatile, not only allowing compression to small file sizes, but also to high-quality, high-bitrate files suitable for production and playout.
However, any discussion about ultra-high resolutions or more HD services in DTH or DVB-T2 terrestrial broadcasts eventually turns to the question of H.264 compression suitability, and this is where HEVC comes in. Professional HD cameras generate a huge amount of raw data, requiring some form of compression before it can be ingested into a production workflow and then transmitted. Dealing with the far larger volume of data that comes with UHD/4K compounds the problem.
High Efficiency Video Coding (HEVC), a video codec jointly developed by ISO/MPEG and ITU-T Video Coding Expert Group, is the natural successor to the Advanced Video Coding (AVC) codec, also known as H.264.
Half the bitrate
HEVC divides the required bitrate by two compared to H.264, for the same level of quality. HEVC can be regarded as a considerable enhancement over H.264, with its ability to take advantage of the significant improvements in CPU power in the intervening years and be able to both deliver UHD over broadcast networks and extend the footprint of HD delivery over broadcast networks such as DTH and DVB-T2. HEVC promises a bandwidth reduction of around 35% – while delivering similar quality to H.264 – in live encoding applications. In the context of video-on-demand (VoD) applications, this increases to around 50% with no quality compromise and half the bitrate.
Adopting HEVC in DVB-T2 terrestrial broadcast in the Middle East is definitely an advantage while the low-resolution SD services are migrating to HD services without occupying additional bandwidth.
A 50% bitrate saving from H.264 means twice as many HD services using the same bandwidth, or the same number of HD services with approximately double the coverage area. There are many new-generation TVs with a built-in DVB-T2 receiver and HEVC decoder. Many DVB-T2 in-car receivers with HEVC decoding are also popping up in the market, taking advantage of DVB-T2 being natively good for mobile reception.
A number of satellite service providers in the Middle East are still providing SD video, which looks very odd when displayed on the new-generation high-resolution TVs. These SD video services need to be migrated to HD services soon to cater to the quality of these TVs.
HEVC leverages more bandwidth savings when DTH services are migrating from SD to HD, and gives the opportunity to add more HD services along with the existing HD services.
Introducing HEVC to HD services will release more bandwidth to roll out ultra-HD channels for DTH satellite providers in the Middle East.
Unlike H.264 macroblocks, H.265 processes information in what’s called Coding Tree Units (CTUs). Whereas macroblocks can span 4×4 to 16×16 block sizes, CTUs can process as many as 64×64 blocks, giving the ability to compress information more efficiently. HEVC also has better motion compensation and spatial prediction than AVC.
Using existing infrastructure
One of the key advantages of the technology is that it allows broadcasters to use existing HD TV network infrastructure to distribute 4K, bearing in mind that an uncompressed use signal needs a bitrate four times higher than an uncompressed HD signal. At this stage we are seeing that a 4K TV signal will need a bitrate of 20-30Mbps for contribution and between 10-15Mbps for distribution, comparable to the bitrate used with a codec H264 for an HD signal.
HEVC adoption in the contribution encoding presents the least scope for disruption. The cost implications will be marginal, as there won’t be a major impact on the consumption of space segment versus HD H.264 contribution. The main impact will be on the renewal of video encoders and decoders to support HEVC.
On the distribution side, the economic impact will be significantly different, as moving from H.264 to HEVC implies renewing set-top boxes. However, the consumer electronics industry moves much faster than the broadcasters and wants to increase fourfold the number of pixels on every device. Without HEVC, this will quadruple the storage requirements for video content and clog the already limited network bandwidths. To bring 4K or UHD to the consumer, the HEVC standard is essential, as it can cut these requirements at least by half.
The broadcast industry moves very slowly. It will have the biggest advantages in cost saving and consumer satisfaction by adopting HEVC. The industry is pushing for additional video enhancement tools such as Higher Dynamic Range, more colour information and better colour representation (BT 2020). UHD support in broadcast may not be feasible without upgrading the infrastructure, and with the advantage that HEVC can provide to UHD video, including it in the infrastructure upgrade is the optimal choice. On the other hand, contribution encoding can heavily benefit from HEVC with reasonable change in infrastructure.
Now is the time for Middle East broadcasters to move to 4K/UHD production, including archiving contribution with HEVC and preparing for future UHD distribution, among other factors. A UHD video downscaled to HD video looks better than native HD video. All these are strong drivers for the widespread adoption of HEVC throughout the Middle East.