codecs

Video: Comparison of EVC and VVC against HEVC and AV1

Posted on by Russell Trafford-Jones

AV1’s royalty-free status continues to be very appealing, but in raw compression is it losing ground now to the newer codecs such as VVC? EVC has also introduced a royalty-free model which could also detract from AV1’s appeal and certainly is an improvement over HEVC’s patent debacle. We have very much moved into an ecosystem of patents rather than the MPEG2/AVC ‘monoculture’ of the 90s within broadcast. What better way to get a feel for the codecs but to put them to the test?

Dan Grois from Comcast has been looking at the new codecs VVC and EVC against AV1 and HEVC. VVC and EVC were both released last year and join LCEVC as the three most recent video codecs from MPEG (VVC was a collaboration between MPEG and ITU). In the same way, HEVC is known as H.265, VVC can be called H.266 and it draws its heritage from the HEVC too. EVC, on the other hand, is a new beast whose roots are absolutely shared with much of MPEG’s previous DCT-based codecs, but uniquely it has a mode that is totally royalty-free. Moreover, its high-performant mode which does include patented technology can be configured to exclude any individual patents that you don’t wish to use thus adding some confidence that businesses remain in control of their liabilities.

Dan starts by outlining the main features of the four codecs discussing their partitioning methods and prediction capabilities which range from inter-picture, intra-picture and predicting chroma from the luma picture. Some of these techniques have been tackled in previous talks such as this one, also from Mile High Video and this EVC overview and, finally, this excellent deep dive from SMPTE in to all of the codecs discussed today plus LCEVC.

Dan explains the testing he did which was based on the reference encoder models. These are encoders that implement all of the features of a codec but are not necessarily optimised for speed like a real-world implementation would be. Part of the work delivering real-world implementations is using sophisticated optimisations to get the maths done quickly and some is choosing which parts of the standard to implement. A reference encoder doesn’t skimp on implementation complexity, and there is seldom much time to optimise speed. However, they are well known and can be used to benchmark codecs against each other. AV1 was tested in two configurations since

AV1 needs special treatment in this comparison. Dan explains that AV1 doesn’t have the same approach to GOPs as MPEG so it’s well known that fixing its QP will make it inefficient, however, this is what’s necessary for a fair comparison so, in addition to this, it’s also run in VBR mode which allows it to use its GOP structure to the full such as AV1’s invisible frames which carry data which can be referenced by other frames but which are never actually displayed.

The videos tested range from 4K 10bit down to low resolution 8 bit. As expected VVC outperforms all other codecs. Against HEVC, it’s around 40% better though carrying with it a factor of 10 increase in encoding complexity. Note that these objective metrics tend to underrepresent subjective metrics by 5-10%. EVC consistently achieved 25 to 30% improvements over HEVC with only 4.5x the encoder complexity. As expected AV1’s fixed QP mode underperformed and increased data rate on anything which wasn’t UHD material but when run in VBR mode managed 20% over HEVC with only a 3x increase in complexity.

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Speaker

Dan Grois Dan Grois
Principal Researcher,
Comcast

Video: Benjamin Bross and Adam Wieckowski on Fraunhofer HHI, VVC, and Compression

Posted on by Russell Trafford-Jones

VVC was finalised in mid-2020 after five years of work. AVC’s still going strong and is on its 26th version, so it’s clear there’s still plenty of work ahead for those involved in VVC. Heavily involved in AVC, HEVC and now VVC is the Fraunhofer Heinrich Hertz Institute (HHI) who are patent holders in all three and for VVC they are, for the first time, developing a free, open-source encoder and decoder for the standard.

In this video from OTTVerse.com, Editor Krishna Rao speaks to Benjamin Bross and Adam Więckowsk both from Fraunhofer HHI. Benjamin has previously been featured on The Broadcast Knowledge talking at Mile High Video about VVC which would be a great video to check out if you’re not familiar with this new codec given before its release.

They start by discussing how the institute is supported by the German government, money received from its patents and similar work as well as the companies who they carry out research for. One benefit of government involvement is that all the papers they produce are made free to access. Their funding model allows them the ability to research problems very deeply which has a number of benefits. Benjamin points out that their research into CABAC which is a very efficient, but complex entropy encoding technique. In fact, at the time they supported introducing it into AVC, which remember is 19 years old, it was very hard to find equipment that would use it and certainly no computers would. Fast forward to today and phones, computers and pretty much all encoders are able to take advantage of this technique to keep bitrates down so that ability to look ahead is beneficial now. Secondly, giving an example in VVC, Benjamin explains they looked at using machine learning to help optimise one of the tools. This was shown to be too difficult to implement but could be replaced by matrix multiplication which and was implemented this way. This matrix multiplication, he emphasises, wouldn’t have been able to be developed without having gone into the depths of this complex machine learning.

Krishna suggests there must be a lot of ‘push back’ from chip manufacturers, which Benjamin acknowledges though, he says people are just doing their jobs. It’s vitally important, he continues, for chip manufacturers to keep chip costs down or nothing would actually end up in real products. Whilst he says discussions can get quite heated, the point of the international standardisation process is to get the input at the beginning from all the industries so that the outcome is an efficient, implementable standard. Only by achieving that does everyone benefit for years to come.e

The conversation then moves on to the open source initiative developing VVenC and VVdeC. These are separate from the reference implementation VTM although the reference software has been used as the base for development. Adam and Benjamin explain that the idea of creating these free implementations is to create a standard software which any company can take to use in their own product. Reference implementations are not optimised for speed, unlike VVenC and VVdeC. Fraunhofer is expecting people to take this software and adapt it for, say 360-degree video, to suit their product. This is similar to x264 and x265 which are open source implementations of AVC and HEVC. Public participation is welcomed and has already been seen within the Github project.

Adam talks through a slide showing how newer versions of VVenC have increased speed and bitrate with more versions on their way. They talk about how some VVC features can’t really be seen from normal RD plots giving the example of open vs closed GOP encoding. Open GOP encoding can’t be used for ABR streaming, but with VVC that’s now a possibility and whilst it’s early days for anyone having put the new type of keyframes through their paces which enable this function, they expect to start seeing good results.

The conversation then moves on to encoding complexity and the potential to use video pre-processing to help the encoder. Benjamin points out that whilst there is an encode increase to get to the latest low bitrates, to get to the best HEVC can achieve, the encoding is actually quicker. Looking to the future, he says that some encoding tools scale linearly and some exponentially. He hopes to use machine learning to understand the video and help narrow down the ‘search space’ for certain tools as it’s the search space that is growing exponentially. If you can narrow that search significantly, using these techniques becomes practical. Lastly, they say the hope is to get VVenC and VVdeC into FFmpeg at which point a whole suite of powerful pre- and post- filters become available to everyone.

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Full transcript of the video
Speakers

Benjamin Bross Benjamin Bross
Head of Video Coding Systems Group,
Fraunhofer Heinrich Hertz Institute (HHI)
Adam Więckowski Adam Więckowski
Research Assistant
Fraunhofer HHI
Krishna Rao Vijayanagar Moderator: Krishna Rao Vijayanagar
Editor,
OTTVerse.com

Video: MPEG-5 Essential Video Coding (EVC) Standard

Posted on by Russell Trafford-Jones

Learning from the patent miss-steps of HEVC, MPEG have released MPEG-5 EVC which brings bitrate savings, faster encoding and clearer licencing terms including a royalty-free implementation. The hope being that with more control over exposure to patent risk, companies large and small will adopt EVC as they improve and launch streaming services now and in the future.

At Mile High Video 2020, Kiho Choi introduced the MPEG 5 Essential Video Coding. Naturally, the motivation to produce a new codec was partly based on the continued need to reduce video bitrates. With estimates of the video traffic share on the internet, both now and in the future all hovering between 75% and 90% any reduction in bitrate will have a wide benefit, best exemplified by Netflix and Facebook’s decision to reduce the bitrate at the top of their ABR ladder during the pandemic which impacted the quality available to viewers. The unspoken point of this talk is that if the top rung used EVC, viewers wouldn’t notice a drop in quality.

The most important point about EVC, which is in contrast to the MPEG/ISO co-defined standard form last year, VVC, is that it provides businesses a lot of control over their exposure to patent royalties. It’s no secret that much HEVC adoption has been hampered by the risk that large users could be approached for licencing fees. Whilst it has made its way into Apple devices, which is no minimal success, big players like ESPN won’t have anything to do with it. EVC tackles this problem in two ways. One is to have a baseline profile which provides bitrate savings over its predecessors but uses a combination of technologies which are either old enough to not be eligible for royalty payments or that have been validated as free to use. Companies should, therefore, be able to use this level of codec without any reasonable concern over legal exposure. Moreover, the main profile which does use patentable technologies allows for each individual part of the profile to be switched off meaning anyone encoding EVC has control, assuming the vendor makes this possible, over which technologies they are using and hence their exposure to risk. Kiho points out that this business-requirements-first approach is new and in contrast to many codecs.

Kiho highlights a number of the individual tools within both the baseline and main codecs which provide the bitrate savings before showing us the results of the objective and subjective testing. Within the EVC docs, the testing methodology is spelt out to allow EVC to be compared against predecessors AVC and HEVC. The baseline codec shows an improvement of 38% against 1080p60 material and 35% for UHD material compared to AVC doing the same tasks yet it achieves a quicker encoder (less compute needed) and the decode is approximately the same. The main profile, being more efficient is compared against HEVC which is, itself, around 50% more efficient than AVC. Against HEVC, Kiho says, EVC main profile produces an improvement of around 30% encoding gain for UHD footage and 25% for 1080p60 footage. Encoding is close to 5x longer and decoder is around 1.5x longer than HEVC.

Kiho finishes by summarising subjective testing of SDR and HDR videos which show that, in contrast to the objective savings which are calculated by computers, in practice perceived quality is higher and enables a higher bitrate reduction, a phenomenon which has been seen in other codec comparisons such LCEVC. SDR results show a 50% encoding gain for 4K and 30% for 1080p60 against AVC. Against HEVC, the main profile is able to deliver 50% coding gains for 4K content and 40% for 1080p60. For HDR, the main profile provides an approximately 35% encoding gain for both 1080p60 and 4k.

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Speakers

Kiho Choi Kiho Choi
Senior Engineer & Technical Lead for Multimedia Standards at Samsung Electronics
Lead Editor of MPEG5 Part 1 Essential Video Coding

Video: Cloud Encoding – Overview & Best Practices

Posted on by Russell Trafford-Jones

There are so many ways to work in the cloud. You can use a monolithic solution which does everything for you which is almost guaranteed by its nature to under-deliver on features in one way or another for any non-trivial workflow. Or you could pick best-of-breed functional elements and plumb them together yourself. With the former, you have a fast time to market and in-built simplicity along with some known limitations. With the latter, you may have exactly what you need, to the standard you wanted but there’s a lot of work to implement and test the system.

Tom Kuppinen from Bitmovin joins Christopher Olekas from SSIMWAVE and host of this Kirchner Waterloo Video Tech talk on cloud encoding. After the initial introduction to ‘middle-aged’ startup, Bitmovin, Tom talks about what ‘agility in the cloud’ means being cloud-agnostic. This is the, yet unmentioned, elephant in the room for broadcasters who are so used to having extreme redundancy. Whether it’s the BBC’s “no closer than 70m” requirement for separation of circuits or the standard deployment methodology for systems using SMPTE’s ST 2110 which will have two totally independent networks, putting everything into one cloud provider really isn’t in the same ballpark. AWS has availability zones, of course, which is one of a number of great ways of reducing the blast radius of problems. But surely there’s no better way of reducing the impact of an AWS problem than having part of your infrastructure in another cloud provider.

Bitmovin have implementations in Azure, Google Cloud and AWS along with other cloud providers. In this author’s opinion, it’s a sign of the maturity of the market that this is being thought about, but few companies are truly using multiple cloud providers in an agnostic way; this will surely change over the next 5 years. For reliable and repeatable deployments, API control is your best bet. For detailed monitoring, you will need to use APIs. For connecting together solutions from different vendors, you’ll need APIs. It’s no surprise that Bitmovin say they program ‘API First’; it’s a really important element to any medium to large deployment.

 

 

When it comes to the encoding itself, per-title encoding helps reduce bitrates and storage. Tom explains how it analyses each video and chooses the best combination parameters for the title. In the Q&A, Tom confirms they are working on implementing per-scene encoding which promises more savings still.

To add to the complexity of a best-of-breed encoding solution, using best-of-breed codecs is part and parcel of the value. Bitmovin were early with AV1 and they support VP9 and HEVC. They can also distribute the encoding so that it’s encoded in parallel by as many cores as needed. This was their initial offering for AV1 encoding which was spread over more than 200 cores.

Tom talks about how the cloud-based codecs can integrate into workflows and reveals that HDR conversion, instance pre-warming, advanced subtitling support and AV1 improvements are on the roadmap while leads on to the Q&A. Questions include whether it’s difficult to deploy on multiple clouds, which HDR standards are likely to become the favourites, what the pain points are about live streaming and how to handle metadata.

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Speakers

Tom Kuppinen Tom Kuppinen
Senior Sales Engineer,
Bitmovin
Moderator: Christopher Olekas
Senior Software Engineer,
SSIMWAVE Inc.