Streaming Forum: HEVC and OTT

"The competitive over-the-top market calls for broadcast quality," said Alain Pellen, Thomson's marketing director for OTT and web TV solutions, "so quality of experience is key to success."

Pellen made his statement during his "HEVC and OTT: Challenges and Opportunities" presentation at the Streaming Forum in London.

He noted that OTT's transition to a broadcast market is evident in multiple areas, with both display sizes and resolutions are increasing, and expectations around 50 fps and 1080 progressive playback are emerging.

Pellen showed statistics that the monthly average video consumption within Europe is 4.5GB of data. Compared to 27GB in North America, which grew at 40% last year, Europe is lower than North America in terms of total peak-time video consumption via OTT: European consumption accounts for only 40% of all peak-time, fixed-network traffic but European consumption is expected will grow by three times within the next three years.

That growth provides an opportunity for H.265/HEVC, given that fixed broadband in the EU is currently 75% xDSL but that 39% of those EU broadband users are below 10Mbps.

"HEVC could be used to reach those customers with two simultaneous HD streams," said Pellen.

Pellen noted that the use of ABR protocols on access networks may not solve the cost issue, as ABR protocols are designed to fill the data pipe. As such, he suggested that HEVC is a better solution than ABR.

"We prefer to jump to a new standard, the HEVC standard," said Pellen, referring to the option of improving H.264 incrementally or shifting focus to H.265 instead. "HEVC halves the H.264 bitrate and addresses Ultra HD."

"HEVC is really an extension of H.264 with improvements," he said. "There are some serious improvements."

The first improvement Pellen noted is the expanded block size within H.265: HEVC can use 64x64 blocks instead of 16x16 block limitation in AVC.

"HEVC brings the capability to encode blocks that are much bigger," he said, "and blocks can be divided into sub-blocks, so that areas with little information can use the large blocks, while areas with higher content detail can be subdivided the block."

"We can spend the bits where they need to be spent," said Pellen, noting that this improvement is probably half of the gain of HEVC over AVC.

The second improvement is greater prediction accuracy, with two additional improvements being lower encoding noise and temporal stability. Both increase subjective quality, thank to the intra-inter prediction accuracy.

"The gain of HEVC, compared to AVC, is based on the initial resolution," he said, adding that HEVC is really the standard to push full HD and beyond, referring to 1080p and 4K.

"We are comfortable we can achieve 50% for 720p and 60% for 1080p," he said. "For SD, we feel we can achieve 40-44% over AVC."

Speaking of the initial HEVC codec that Thomson has created, Pellen says that it is similar to well-mastered H.264 technology. This first implementation requires five times the resources to encode H.265 versus H.264 and is not completely optimized.

Pellen said he expect efficiency will improve over time, illustrating this point with a chart of H.264 optimization from 2003 until the present. Thomson's H.264 codec had a 50% gain within the first six years, but Pellen noted it took almost a decade to get to 68% improvement.

On the HEVC front, Pellen said that a 50% gain could be achieved within three years of the standard adoption (early 2013), based on learnings from how to implement the H.264 codec. The first launch of the Thomson software-based H.265 codec generates about a twenty per cent decrease in bandwidth.

Another way to look at it, though, is the equivalent bandwidth for today's 720p25 will allow 720p50 delivery by mid-2014, which is beneficial for sports content: 50 frames per second removes the jerkiness evident in sports content that's normally broadcast at 25 frames per second.

What about Ultra HD? Pellen touched briefly on Ultra HD and predicted the target bitrate for 2160p50 (4K) will be 12-15Mbps within the next three years.

Finally, when it comes to implementing HEVC, Pellen said it's no longer a technical barrier.

"Encoding is not the blocking part," he said, noting that players and decoders are not yet readily available in the market, and that interoperability and licensing issues both need to be addressed.

Watch the full presentation below:

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