ATSC Chief IDs 5 HDR Proposals as Likely Amendments to ATSC 3.0 Video Book
The A/341 document on ATSC 3.0 video that went out for ballot late January for elevation to the status of a proposed standard (see 1701200004) largely is silent on choosing a preferred high-dynamic-range technology for the next-generation broadcast system. A/341 does express dual support for perceptual quantization HDR systems like HDR10 and Dolby Vision and also the hybrid log-gamma approach proposed for HDR broadcasts by BBC and NHK.
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But now ATSC’s Technology Group 3, which supervises the framing of ATSC 3.0, “is considering amendments” to add five HDR technologies to A/341, ATSC President Mark Richer emailed us Wednesday. TG3's intent is to float the five technology amendments as candidate standards, each of which would go out for a vote to ATSC’s membership, Richer previously told us.
The five technology proposals, which Richer disclosed to us for the first time publicly, draw heavily from existing standards already on the books at the European Telecommunications Standards Institute (ETSI), the ITU and the Society of Motion Picture and TV Engineers. Several of the proposals also prominently feature “supplemental enhancement information” (SEI) messaging used in processing images and data for decoding or display.
SEI messaging clearly is a hot topic these days, judging from the more than three dozen patents published on the subject just since Christmas at the U.S. Patent and Trademark Office. Apple, Arris, Canon, Dolby Labs, Fujitsu, Hitachi Maxell, Huawei, LG, Microsoft, Nokia, Qualcomm, Samsung, Sharp, Sony, STMicroelectronics and Thomson Licensing all were among those filing inventions at PTO that rely on SEI messaging in a wide variety of ways, including for coding and converting HDR and wide color gamut signals, 3D rendering, motion estimation and virtual and augmented reality.
Of the five technologies proposed to become A/341 amendments, one would be a “full range” document that would let Serial Digital Interface cabling that studios use to interconnect digital video equipment carry 10-bit “sample code values” over longer distances, Richer told us. Another amendment would incorporate ICtCp, the “luminance/chrominance representation” that is an alternative to YCrCb protocol, Richer said. ICtCp is now specified in ITU’s BT.2100 and version 4 of the High Efficiency Video Coding standard, Richer said. ICtCp is also one of the backbones of Dolby Vision, and an undated Dolby white paper touted it as a “more perceptually uniform” color representation than YCrCb, which is a staple of HDR10.
A proposed “2094-10" amendment for A/341 “draws on concepts” from the SMPTE 2094-10 standard that supports Dolby Vision “and proposes a new HEVC SEI message to transmit similar information, as well as other information contained in SMPTE 2094-1,” Richer told us. By design, HEVC signals can include SEI messages that, for instance, help a TV set down-convert wide color gamut signals for more accurate display on an older TV set. Similar, but not identical, SEI messaging is included for informational purposes in CTA 861-G, Richer said.
CTA 861-G, finalized as a standard in November, specifies four different types of what are called Extended InfoFrames to carry HDR dynamic metadata “that is usually, but not always, delivered as SEI messages,” Brian Markwalter, CTA senior vice president-research and standards, emailed us Thursday. “Support for SMPTE 2094-10 is accommodated through one of the Extended InfoFrames (Type 1) in a Display Management message,” Markwalter said. “The information conveyed in this DM message corresponds to the metadata specified in SMPTE ST 2094-1 and SMPTE ST 2094-10.” The CTA working group that wrote CTA-861-G recognized that work on SEI messages continues in other standards organizations, and future versions of CTA-861 “may specify the data format for future versions of type 1 metadata,” Markwalter said.
Of the two remaining technology proposals up for A/341 amendments, both have involved the work of Philips and other technology companies. One proposal, for “Color Remapping Information,” is another kind of HEVC SEI message that's used for the HDR system jointly proposed by Philips and Technicolor, to improve compatibility between HDR and standard dynamic range signals and displays. CRI “specifies a method for transforming images in a video sequence using a pipeline of processing blocks which are commonly available on CE devices, particularly Blu-ray players,” Richer told us.
The other proposal is for an “SL-HDR1" amendment that covers an HDR system from STMicroelectronics, Philips, CableLabs and Technicolor. Now standardized at the ETSI as the TS 103 433 spec, SL-HDR1 uses SEI messages to let an existing SDR TV network carry both HDR and SDR signals, without the need to waste airspace on simulcasting separate HDR and SDR versions. The SL-HDR1 solution “transforms HDR to SDR+metadata prior to encoding, and inverts the process after decoding,” Richer told us. “The value of this transform is to deliver HDR and SDR simultaneously to heterogeneous devices without simulcasting."