Video: LCEVC, The Compression Enhancement Standard

MPEG released 3 codecs last year, VVC, LCEVC and EVC. Which one was unlike the others? LCEVC is the only one that is an enhancement codec, working in tandem with a second codec running underneath. Each MPEG codec from last year addressed specific needs with VVC aiming at comprehensive bitrate savings while EVC aims to push encoding further whilst having a patent-free base layer.

In this talk, we hear from Guido Meardi from V-Nova who explains why LVECV is needed and how it works. LCEVC was made, Guido explains, to cater to an increasingly crowded network environment with more and more devices sending and receiving video both in residential and enterprise. LCEVC helps by reducing the bitrate needed for a certain quality level but, crucially, reduces the computation needed to achieve good quality video which not only benefits IoT and embedded devices but also general computing.

LCEVC uses a ‘base codec’ which is any other codec, often AVC or HEVC, which runs at a lower resolution than the source video. By using this hybrid technique, LCEVC aims to get the best video compression out of the codec yet by running the encode at a quarter resolution, allowing this to be done on low-power hardware. LCEVC then deals with reconstructing two enhancement layers and a, relatively simple, super-resolution upsample. This is all achieved with a simple toolset and all of the LCEVC computation can be done in CPU, GPU or other types of computation; it’s not bound to hardware acceleration.

Guido presents a number of results from tests against a whole range of codecs from VVC to AV1 to plain old AVC. These tests have been done by a number of people including Jan Ozer who undertook a whole range of tests. All of these tests point to the ability of LCEVC to extend bandwidth savings of existing codecs, new and old.

Guido shows an example of a video only comprising edges (apart from mid-grey) and says that LCEVC encodes this not only better than HEVC but also with an algorithm two orders of magnitude less. We then see an example of a pure upsample and an LCEVC encode. Upsampling alone can look good, but it can’t restore information and when there are small textual elements, the benefit of having an enhancement layer bringing those back into the upsampled video is clear.

On the decode side, Guido presents tests showing that decode is also quicker by at least two times if nor more, and because most of the decoding work is involved in decoding the base layer, this is still done using hardware acceleration (for AVC, HEVC and other codecs depending on platform). Because we can still rely on hardware decoding, battery life isn’t impacted.

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Speakers

Guido Meardi Guide Meardi
CEO & Co-Founder,
V-Nova

Video: Low-latency DASH Streaming Using Open Source Tools

Low Latency Dash also known as LL-DASH is a modification of MPEG DASH to allow it to operate with close to two seconds’ latency bringing it down to meet, or beat, standard broadcast signals.

Brightcove’s Bo Zhang starts by outlining the aims and methods of getting there. For instance, he explains, the HTTP 1.1 Chunked Transfer element is key to low-latency streaming as it allows the server to start sending a video segment as its being written, not waiting until the file is complete. LL-DASH also has the ability to state an availability window (‘availabilityTimeOffset’).

As LL-MPEG DASH is a living standard, there are updates on the way: Resync points will allow a player to receive a list of places where it can join a stream using SAP types in the ISO-BMFF spec, the server can send a ‘service description’ to the player which can use the information to adjust its latency. Event messages can now be inserted in the middle of segments.

Bo then moves on to explain that he and the team have set up and experiment to gain experience with LL-DASH and test overall latency. He shows that they decided to stream RTMP out of OBS, into a github project called ‘node-gpac-dash’ then to the dash.js player all. between Boston and Seattle. This test runs at 800×600, 30fps with a bitrate of 2.5Mbps and shows results of between 2.5 and 5 seconds depending on the network conditions.

As Bo moves towards the Q&A, he says that low-latency streaming is less scalable because a TCP connection needs to be kept open between the player and the CDN which is a burden.
Another compromise is that smaller chunk sizes in LL-DASH give reduced latency but IO increases meaning sometimes you may have to increase the chunk sizes (and hence latency of the stream) to allow for better performance. He also adds that adverts are more difficult with low-latency streams due to the short amount of time to request and receive the advertising.

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More detail about the experiments in this talk can be found in Bo’s
blog post.
Speakers

Bo Zhang Bo Zhang
Staff Video System Engineer, Research
Brightcove

Video: The Video Codec Landscape 2020

2020 has brought a bevy of new codecs from MPEG. These codecs represent a new recognition that the right codec is the one which fits your hardware and your business case. We have the natural evolution of HEVC, namely VVC which trades on complexity to achieve impressive bit rate savings. There’s a recognition that sometimes a better codec is one that has lower computation, namely LCEVC which enables a step-change in quality for lower-power equipment. And there’s also EVC which has a license-free mode to reduce the risk for companies which prefer low-risk deployments.

Christian Feldmann from Bitmovin takes the stage in this video to introduce these three new contenders in an increasingly busy codec landscape. Christian starts by talking about the incumbents namely AVC, HEVC, VP9 and AV1. He puts their propositions up against the promises of these new codecs which are all at the point of finalisation/publication. With the current codecs, Christian looks at what the hardware and software support is like as well as the licencing.

EVC (Essential Video Codec) is the first focus of the presentation whose headline feature is more reliably licence landscape. The first offer is the baseline profile which has no licencing as it uses technologies which are old enough to be outside of patents. The main profile does require licencing and does allow much better performance. Furthermore, the advanced tools in the main profile can each be turned off individually hence avoiding patents that you don’t want to licence. The hope is that this will encourage the patent holders to licence the technology in a timely manner else the customer can, relatively easily, walk away. Using the baseline only should provide 32% better than AVC and the main profile can give up to a 25% benefit over HEVC.

LCEVC (Low Complexity Enhancement Video Coding) is next which is a new technique for encoding which is actually two codecs working together. It uses a ‘base’ codec at low resolution like AVC, HEVC, AV1 etc. This low fidelity version is then accompanied by enhancement information so that the low-resolution base can be upscaled to the desired resolution can be corrected with relevant edges etc. added. The overall effect is that complexity is kept low. It’s designed as a software codec which can fit into almost any hardware by using the hardware decoders in SoCs/CPUs (i.e. Intel QuickSync) plus the CPU itself which deals with the enhancement application. This ability to fit around hardware makes the codec ideal for improving the decoding capability to existing hardware. It stands up well against AVC providing at least 36% improvement and at worst improves slightly upon HEVC bitrates but with much-reduced encoder computation.

VVC (Versatile Video Coding) is discussed by Christian but not in great detail as Bitmovin will be covering that separately. As an evolution of HEVC, it’s no surprise that bitrate is reduced by at least 40%, though encoding complexity has gone up 10-fold. This is similar to HEVC compared to its predecessor AVC. VVC has some built-in features not delivered as standard before such as special modes for screen content (such as computer games) and 360-degree video.

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Speaker

Christian Feldmann Christian Feldmann
Lead encoding engineer,
Bitmovin

Video: ATSC 3.0 Seminar Part III

ATSC 3.0 is the US-developed set of transmission standards which is fully embracing IP technology both over the air and for internet-delivered content. This talk follows on from the previous two talks which looked at the physical and transmission layers. Here we’re seeing how IP throughout has benefits in terms of broadening choice and seamlessly moving from on-demand to live channels.

Richard Chernock is back as our Explainer in Chief for this session. He starts by explaining the driver for the all-IP adoption which focusses on the internet being the source of much media and data. The traditional ATSC 1.0 MPEG Transport Stream island worked well for digital broadcasting but has proven tricky to integrate, though not without some success if you consider HbbTV. Realistically, though, ATSC see that as a stepping stone to the inevitable use of IP everywhere and if we look at DVB-I from DVB Project, we see that the other side of the Atlantic also sees the advantages.

But seamlessly mixing together a broadcaster’s on-demand services with their linear channels is only benefit. Richard highlights multilingual markets where the two main languages can be transmitted (for the US, usually English and Spanish) but other languages can be made available via the internet. This is a win in both directions. With the lower popularity, the internet delivery costs are not overburdening and for the same reason they wouldn’t warrant being included on the main Tx.

Richard introduces ISO BMFF and MPEG DASH which are the foundational technologies for delivering video and audio over ATSC 3.0 and, to Richard’s point, any internet streaming services.

We get an overview of the protocol stack to see where they fit together. Richard explains both MPEG DASH and the ROUTE protocol which allows delivery of data using IP on uni-directional links based on FLUTE.

The use of MPEG DASH allows advertising to become more targeted for the broadcaster. Cable companies, Richard points out, have long been able to swap out an advert in a local area for another and increase their revenue. In recent years companies like Sky in the UK (now part of Comcast) have developed technologies like Adsmart which, even with MPEG TS satellite transmissions can receive internet-delivered targeted ads and play them over the top of the transmitted ads – even when the programme is replayed off disk. Any adopter of ATSC 3.0 can achieve the same which could be part of a business case to make the move.

Another part of the business case is that ATSC not only supports 4K, unlike ATSC 1.0, but also ‘better pixels’. ‘Better pixels’ has long been the way to remind people that TV isn’t just about resolution. ‘Better pixels’ includes ‘next generation audio’ (NGA), HDR, Wide Colour Gamut (WCG) and even higher frame rates. The choice of HEVC Main 10 Profile should allow all of these technologies to be used. Richard makes the point that if you balance the additional bitrate requirement against the likely impact to the viewers, UHD doesn’t make sense compared to, say, enabling HDR.

Richard moves his focus to audio next unpacking the term NGA talking about surround sound and object oriented sound. He notes that renderers are very advanced now and can analyse a room to deliver a surround sound experience without having to place speakers in the exact spot you would normally need. Options are important for sound, not just one 5.1 surround sound track is very important in terms of personalisation which isn’t just choosing language but also covers commentary, audio description etc. Richard says that audio could be delivered in a separate pipe (PLP – discussed previously) such that even after the
video has cut out due to bad reception, the audio continues.

The talk finishes looking at accessibility such as picture-in-picture signing, SMPTE Timed Text captions (IMSC1), security and the ATSC 3.0 standards stack.

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Speaker

Richard Chernock Richard Chernock
Former CSO,
Triveni Digital