What Does DVB’s Adoption of VVC Mean for the 8K Community?
To get some deeper understanding into what DVB’s adoption of VVC means, especially for the 8K community, we reached out to the organization and had a chat with Elfed Howells and Paul Szucs.
Elfed represents High Silicon/Huawei at DVB and chairs its Promotion & Communications Module. Paul is the Vice-Chair of the DVB technical group on codec adoption. He chaired the task force adopting VVC and is Senior Manager of Technology Standards at Sony Europe.
The key message from our meeting
Technology adoption by DVB
Since 1993, the DVB has designed open technical specifications for digital media delivery. The details of the working group activities are confidential. However, we know that the panel of next-generation codecs that have been presented comprise:
- MPEG EVC (MPEG-5 part 1)
- LCEVC (MPEG-5 part 2)
We’ve already covered the news in the 8K Monitor that VVC has just been accepted into the DVB toolbox, making VVC a DVB-approved codec.
No comparisons are made between codecs, so VVC hasn’t “won”, just it has been looked at first and fulfils the commercial requirements, part of which are based on technical performance.
VVC has been examined since a September 2020 workshop. That was the actual kick-off, as some preliminary ad hoc work had already been done within DVB to establish the rationale for considering next-generation video codecs. The working group starts with use cases leading to commercial requirements (VVC saw this phase in Q1 21) and technical specifications as the last step.
Almost a decade ago, DVB defined UHD Phase 1 that went up to 4K resolution and an associated Phase 2 that also supports HDR and HFR. Both profile groups ensure interoperability for streaming and broadcast services.
8K profiles were added to HEVC for UHD Phase 2 services in October 2021. Note that HEVC, standardized in 2013, has been in the toolbox for several years, but the DVB profiles only previously went up to 4K. So as of March 2022, there are two DVB-compliant ways of compressing 8K: HEVC and VVC, and very probably, others in the pipeline, such as AV1 and AVS3, will join them later in the year.
VVC adoption process
VVC is the first of the list of candidate Next-Generation codecs above to be added to the toolbox – the working group is “proud to have got it out so quickly”. This decision must not imply a codec race, and VVC’s inclusion in no way means that other candidates are less worthy. I was, however, told that EVC is not currently being pursued as it was never formally proposed. It could, of course, come back into consideration.
Three other codecs are still being actively considered (AV1, AVS3 and LCEVC).
8K video resolution up to 7680×4320 pixels is a critical commercial requirement that each solution must pass to become a Next-Generation DVB codec. But the 8K experience goes beyond mere resolution, and DVB also stated that “High dynamic range (HDR) and high frame rates (HFR) are also to be supported”.
DVB’s Jason Power wrote in DVB Scene, “Scaling 8K video service delivery to end-users will require more efficient video codecs. This applies to both broadcast (DVB-S2/C/T2) and broadband (DVB-DASH) delivery. One of the goals of this work is to enable 8K standard frame rate delivery over legacy broadcast multiplexes at ‘excellent’ video quality”.
Subject to successfully validating technical and IPR compliance, DVB expects to add the other candidate codecs to its toolbox to support 8K in 2022.
As DVB had no prior data, required compression gains were only specified up to 4K resolution, which must be at least 27% for broadcast and 30% for broadband, compared to existing codecs like HEVC. Therefore, we can expect at least the same for 8K content, probably more.
Other standard requirements
DVB requires Next-Gen codecs to be readily deployable within DVB-DASH, CMAF and DVB-I environments.
High Frame Rate helps the visual experience, “even if it’s not yet ready for commercial deployment,” said Szucs. He clarified that “DVB isn’t into the business of specifying a minimum frame rate but acknowledges that greater resolutions may call for greater frame rates.”
Tidying up the standards
Profiles are consensus-based, which avoids non-sensical combinations within a profile. For example, some old legacy TV features like “interlaced” have been dropped from the 8K profiles. DVB considers cleaning out any legacy or profiles no longer in use whenever new operating points are added.
DVB doesn’t perform any codec performance testing; they rely on member organizations to provide detailed documentation of tests which is then evaluated. Subjective testing needs to have been conducted by independent labs. With objective tests, reference material must be supplied so other members can perform the same tests.
DVB testing guidelines are based on the MPEG testing guidelines, which rely on methods developed in the ITU.
Any subjective testing is also “brought in” by the codec proponents then evaluated by the DVB working group.
HEVC 8K functionality test content can be found here. The HLG and PQ10 streams were created using uncompressed high dynamic range (HDR) content. The test sequence has been up-converted from 3840×2160 to 7680×4320 using the FFmpeg bicubic interpolation filter.
The purpose of these streams is to show how a DVB 8K stream should be signaled and constructed, not to show or test video quality or compression rate, nor is it intended for performance testing.
VTM – the reference implementation from MPEG – is the preferred codec for testing.
A note on AVS
AVS has been running for over two decades. This Chinese consortium has produced three major codecs that can be compared to MPEG codec generations. DVB is considering its adoption into the toolbox at the request of several global member organizations.
|Chinese standard||MPEG equivalent|
*AVS1 and AVS2 are not included in the DVB toolbox, but AVS3 is being considered for inclusion as part of the Next Generation Video Coding process.
8K Monitor comment
8K Association executive director Chris Chinnock commented on DVB’s adoption of VVC, “DVB looks to be the first broadcast organization to add VVC to its toolbox. VVC is the MPEG-approved follow-on to HEVC and should ultimately deliver similar quality video signals at close to half the data rate required by HEVC. But this benefit comes at the cost of added encoding complexity. This can be very significant in the early stages of the codec commercialization but has historically been greatly reduced over time. VVC is thought to be a key enabler for 8K video services.”