MPEG is releasing three new video codecs in 2020-2021 called Versatile Video Coding (H.266), Essential Video Coding (EVC MPEG-5 Part 1), and Low Complexity Enhancement Video Coding (LCEVC MPEG-5 Part 2). Let’s take a look at the highlights of each of these codecs and what they bring to the table.
Video Compression is Critical To Your Infrastructure
Video traffic is growing by the day and that is not going to stop any time soon. The pandemic might have stymied other industries, but, has actually given a filip to the streaming industry, because people are stuck indoors, and watching videos provides a much-needed escape from the daily routine!
Video Compression is a critical component in the video delivery pipeline and can make a massive make-or-break impression in the minds of the end-user. If you “tune” your encoders to maximize video quality, you’ll have to compromise on compression efficiency and spend more bits; and vice-versa. If you compromise on compression efficiency and create larger files, then you will have to spend more on CDN delivery costs.
So, the goal of every encoder team is to create a fine-balance between quality and bitrate. In other words, balance video quality with dollars.
The easiest way to perform this balancing act is to upgrade to the best encoder or encoding technology on the market. Hypothetically, this is simple, but practically, this is difficult. You need to make sure that the quality-complexity-efficiency trade-offs are met and decoder support is available amongst other things.
The Failure of HEVC
When we talk about encoders, the discussion isn’t complete without mentioning H.264/AVC which is still ruling supreme since its introduction by MPEG (in 2003, I think). The MPEG announced a successor to H.264/AVC and called it H.265/HEVC (High Efficiency Video Coding) that had a slew of new coding tools such as quadtree decomposition, new picture types, SAO filtering, etc.
However, HEVC turned out to be a flop and the failure of HEVC had almost nothing to do with the algorithms. For HEVC R&D teams, getting 20-30% gains over AVC was easy.
You may disagree, but, as someone who wrote HEVC code for years, I stand by what I said.
The “failure” of MPEG’s H.265/HEVC was due to patent-pools and licensing issues and this created the need for a new codec to fill the gap left by HEVC and to replace H.264/AVC (which by-design will struggle to compress 4K, UHD, and large resolutions).
In this regards, MPEG has announced that three new video codecs will soon be standardized and they are :-
- Versatile Video Coding (H.266)
- Essential Video Coding (EVC MPEG-5 Part 1)
- Low Complexity Enhancement Video Coding (LCEVC MPEG-5 Part 2)
Let’s take a quick look at the objective of each of these codecs and see what gap they’re trying to plug, shall we?
Versatile Video Coding – VVC / H.266
Touted as a successor to HEVC, the Versatile Video Coding standard has a lofty goal of achieving at least a 30% improvement in compression efficiency over HEVC. This should be doable considering the allowance of the “10x complexity increase” that the committee has provided.
In the MPEG Requirements document for VVC (H.266), a few interesting points stand out with regards to compression efficiency, coding complexity, etc.
- A substantial improvement in compression efficiency compared to HEVC Main Profile is required for the target application(s); at no point of the entire bit rate range shall it be worse than existing standard(s). 30% bitrate reduction for the same perceptual quality is sufficient for some important use-cases and may justify a future video coding standard. Other use-cases may require higher bit-rate reductions such as 50%.
- Encoding complexity of approximately 10 times or more than that of HEVC is acceptable for many applications.
- The standard shall enable the use of efficient prediction structures (e.g. so-called open groups of pictures) without compromising from the fast and seamless representation switching capability between representations of different properties, such as different spatial resolutions.
- Support for progressive scanning shall be required for all Profiles and Levels.
What stands out to me the most in the Requirements document are the references to “fast-switching” and “progressive scanning“. This is a clear indication of the importance that the MPEG body is placing on OTT streaming (and the implicit absence of interlaced video in OTT).
This was a HUGE problem in HEVC where interlaced support was an after-thought; and it lead to a lot of code-wrangling to retro-fit interlaced support into commercial codecs. I hope VVC does not tread the same interlaced path.
The second comment about fast-switching is interesting and might put pressure on codec vendors to insert more IDRs in the bitstream to support smaller segment sizes and clean, fast, switching between profiles in the ABR bitrate ladder. The reference to open-gops is interesting, because Open-GOPs are very helpful in increasing compression efficiency – so this is something fun to watch out for.
Whenever a discussion about MPEG’s video codecs comes up, the elephant in the room has to be licensing. Fraunhofer HHI said in their newsletter that,
A uniform and transparent licensing model based on the FRAND principle (i.e., fair, reasonable, and non-discriminatory) is planned to be established for the use of standard essential patents related to H.266/VVC. For this purpose, the Media Coding Industry Forum (MC-IF) was founded.
I hope VVC pans out because I’d love to see it in action crunching 4K/8K videos!
Essential Video Coding – EVC (MPEG-5 Part 1)
MPEG-5 EVC or Essential Video Coding is an MPEG standard backed by Samsung, Huawei, Qualcomm, Divideon as a response to the patent pool mess that HEVC ran it that essentially stymied large-scale adoption of a powerful video compression standard.
The requirements of the EVC standard were very clearly specified by MPEG as follows –
- The test model should consist of two tool sets: a base and an enhanced tool set
- The base tool set should be configured with tools that were made public more than 20 years ago or for which a Type 1 declaration is received
- There should be additional tools in the enhanced tool set, each of which shall provide a significant improvement in coding efficiency and be capable of being cleanly switched off on an individual basis
EVC’s aim is crystal-clear – provide a royalty-free option for content producers while also providing adequate tools, algorithms, and knobs to produce higher quality video (than the base tool set). And, the enhancement layer’s tools (also referred to as the Main layer) will be subject to royalties.
Sounds good, eh?
It is also interesting to note the following sentence from the IBC 2019 paper on EVC and I quote,
No considerations have been taken on licensing aspects of the technology other than a requirement for FRAND commitment by the contributors. Commercial aspects, and in particular, licensing aspects have been handled externally and independently of MPEG.
They’ve been handled, huh? Okay cool, but I still cross my fingers and say a prayer when I hear “MPEG” and “Licensing” in the same sentence.
Let’s hope that EVC is adopted and supported in the industry quickly – its a good concept and means well.
In a future article, we will do a deep dive into the tools supported in the Base and the Main layers of EVC.
Low Complexity Enhancement Video Coding – LCEVC (MPEG-5 Part 2)
MPEG-5 Part 2 LCEVC is being introduced with the aim of increased compression efficiency for existing codecs at little or no-increase in coding complexity by using a base bitstream and an enhancement bitstream.
The LCEVC codec’s output is essentially a combination of a “base bitstream” produced by an existing video codec such as AVC, HEVC, VP9, AV1, etc. along with enhancement layers that can be used conditionally to improve the quality of the video.
If the decoder/end-device supports LCEVC, the enhancement layers are decoded, else, the base codec alone is used to decode the bitstream and the video is rendered to the user. This ensures backward-compatibility and encourages roll-out of the LCEVC codec without the fear of breaking the end-user’s experience.
This concept is nicely captured in the figure below taken from Guido Meardi’s presentation at the ITU Workshop on the Future of Media in Geneva.
For further details on LCEVC, please read
On a final note, V-Nova has been instrumental in driving the LCEVC standard through their research and work on the Perseus codec. More information on that here.
I think 2020 and 2021 present great challenges and opportunities for the field of video compression.
With consumption increasing due to the COVID-19 situation, most content providers are under the gun to reduce their streaming costs. Dropping the bitrates is one way of reducing your streaming costs, but, conversely, it will be hard to compete with the likes of Netflix, Hulu, HBO, Peacock, fuboTV, DAZN with poor video quality.
If the compression experts can pull off VVC’s goals of 30% bitrate savings over HEVC, then it will be a huge win. The only thing they’ll have to ensure is that they don’t blow their foot off with licensing issues (a-la-HEVC). If things work out properly, VVC should be a good competitor to AV1 especially at high resolutions such as 4K and 8K.
However, that being said, I think that among the three codecs (i.e, VVC, EVC, and LCEVC), EVC and LCEVC have an advantage over VVC mainly due to the fact that they are explicitly trying to improve existing codecs, or avoid licensing issues, and decrease coding complexity (or no change at all).
If LCEVC can get support from the player companies (i.e., support for the enhancement layers), then, it becomes very attractive for companies who want to continue using their existing codecs (AVC, HEVC, or AV1) and squeeze more bits/watt!
Who would say no to that?
Let the codec wars begin! 🎺
PS: I know they’ve begun, but, it just feels good saying that 🙂