ITU to ratify both BBC and Dolby HDR standards

The persistent question mark hanging over the introduction of High Dynamic Range to the home is about to be settled. The two proposals before standards body the ITU have for a while been thought to be competing for the same prize. With diplomacy fitting of a United Nations agency, the ITU is understood to be ratifying both as standard on July 4.

The two recommendations for High Dynamic Range are Hybrid Gamma Log (HLG), devised by the BBC and NHK; and PQ [Perceptual Quantizer], which was principally developed by Dolby.

“These are two different, not competing, positions to solving two different problems,” says Andy Quested, BBC HD & UHD, head of technology. “Both solve their own problem elegantly. PQ is focused more on the display and is based on what we see in controlled environments like the cinema. The other acknowledges that broadcast TV is a bit of a wild west and that it is harder to control display characteristics.”

He adds: “The BBC NHK version is primarily designed with a live broadcast environment in mind and with a infrastructure through which a signal has to pass, which in the US can include multiple syndicated broadcasters.”

Dolby’s proposal is aimed more at HDR mastering for recorded content such as Hollywood movies and studio drama for home entertainment.

“We believe the market will sort out which format it wants, as it always does,” says Quested. “In the broadcast environment it is important to be able to interchange – or make a seamless conversion – between a PQ HDR with a HLG HDR so that programming of both types can be run on the same channel.”

Quested added that he felt HDR “vital” to the quality of a UHD picture and far more so than resolution.

The Digital Production Partnership (DPP) the standards body for file delivery organised by the main UK broadcasters will incorporate the ITU’s recommendations into its guidelines for UHD delivery.

Backwards compatibility focus

The BBC has been working with the Joint Collective Team on Video Coding (JCT-VC) to standardise the required signalling in ITU-T H.265 (HEVC) compression, which allows both backwards compatible and ‘non-backwards compatible’ modes of operation for the HLG solution.

In a blog post the BBC explains that backwards compatibility is key for broadcasters as it allows a single UHDTV programme feed to serve both the new HDR enabled UHDTV sets, as well as standards compliant standard dynamic range (SDR) UHDTVs that have already been purchased.

“It will also save us money in TV production as only critical monitors need to be HDR capable, the vast majority of monitoring can continue to use SDR monitors and PC screens,” it states.

To demonstrate the concept of HDR and the technical capability of Hybrid Log Gamma BBC R&D shot tests including of from a RIB boat with BT Research and BT Sport capturing footage of the America’s Cup World Series in the Solent and footage shot at 2160p 100 fps at the rehearsal for the Eurovision 60th Anniversary Party at the Hammersmith Apollo with a camera loaned from Panasonic.

Other tests using HLG included Sky Europe’s broadcast of the DFL SuperCup in UHD with HDR, a trial by NASA in conjunction with Harmonic and the Vatican’s broadcast of the Ceremony of the Opening of the Holy Door, by the Pope Francis, in HLG HDR UHDTV – a broadcast which is shortlisted for an IBC 2016 Innovation Award.

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