Video: Outlook on the future codec landscape

VVC has now been released, MPEG’s successor to HEVC. But what is it? And whilst it brings 50% bitrate savings over HEVC, how does it compare to other codecs like AV1 and the other new MPEG standards? This primer answers these questions and more.

Christian Feldmann from Bitmovin starts by looking at four of the current codecs, AVC, HEVC, VP9 and AV1. VP9 isn’t often heard about in traditional broadcast circles, but it’s relatively well used online as it’s supported on Android phones and brings bitrate savings over AVC. Google use VP9 on Youtube for compatible players and see a higher retention rate. Netflix and Twitch also use it. AV1 is also in use by the tech giants, though its use outside of those who built it (Netflix, Facebook etc.) is not yet apparent. Christian looks at the compatibility of the codecs, hardware decoding, efficiency and cost.

Looking now at the other upcoming MPEG codecs, Christian examines MPEG-5 Essential Video Coding (EVC) which has two profiles: Baseline and Main. The baseline profile only uses technologies which are old enough to be outside of patent claims. This allows you to use the codec without the concern that you may be asked for a fee from a patent holder who comes out of the woodwork. The main profile, however, does have patented technology and performs better. Businesses which wish to use this codec can then pay licences but if an unexpected patent holder appears, each individual tool in the codec can be disabled, allowing you to protect continue using, albeit without that technology. Whilst it is a shame that patents are so difficult to account for, this shows MPEG has taken seriously the situation with HEVC which famously has hundreds of licensable patents with over a third of eligible companies not part of a patent pool. EVC performs 32% better than AVC using the baseline profile and 25% better than HEVC with the main profile.

Next under the magnifying glass is Low Complexity Enhancement Video Coding (LCEVC). We’ve already heard about this on The Broadcast Knowledge from Guido, CEO of V-Nova who gave a deeper look at Demuxed 2019 and more recently at Streaming Media West. Whilst those are detailed talks, this is a great overview of the technology which is actually a hybrid approach to encoding. It allows you to take any existing codec such as AVC, AV1 etc. and put LCEVC on top of it. Using both together allows you to run your base encoder at a lower resolution (say HD instead of UHD) and then deliver to the decoder this low-resolution encode plus a small stream of enhancement information which the decoder uses to bring the video back up to size and add back in the missing detail. The big win here, as the name indicates, is that this method is very flexible and can take advantage of all sorts of available computing power in embedded technology as and in servers. In set-top boxes, parts of the SoC which aren’t used can be put to use. In phones, both the onboard HEVC decoding chip and the CPU can be used. It’s also useful in for automated workflows as the base codec stream is smaller and hence easier to decode, plus the enhancement information concentrates on the edges of objects so can be used on its own by AI/machine learning algorithms to more readily analyse video footage. Encoding time drops by over a third for AVC and EVC.

Now, Christian looks at the codec-du-jour, Versatile Video Codec (VVC), explaining that its enhancements over HEVC come not just from bitrate improvements but techniques which better encode screen content (i.e. computer games), allow for better 360 degree video and reduce delay. Subjective results show up to 50% improvement. For more detail on VVC, check out this talk from Microsoft’s Gary Sullivan.

The talk finishes with answers so audience questions: Which will be the winner, what future device & hardware support will be and which is best for real-time streaming.

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Speakers

Christian Feldmann Christian Feldmann
Team lead, Encoding,
Bitmovin

Video: AV1 – A Reality Check

Released in 2018, AV1 had been a little over two years in the making at the Alliance of Open Media founded by industry giants including Google, Amazon, Mozilla, Netflix. Since then work has continued to optimise the toolset to bring both encoding and decoding down to real-world levels.

This talk brings together AOM members Mozilla, Netflix, Vimeo and Bitmovin to discus where AV1’s up to and to answer questions from the audience. After some introductions, the conversation turns to 8K. The Olympics are the broadcast industry’s main driver for 8K at the moment, though it’s clear that Japan and other territories aim to follow through with further deployments and uses.

“AV1 is the 8K codec of choice” 

Paul MacDougall, Bitmovin
 CES 2020 saw a number of announcements like this from Samsung regarding AV1-enabled 8K TVs. In this talk from Google, Matt Frost from Google Chrome Media explains how YouTube has found that viewer retention is higher with VP9-delivered videos which he attributes to VP9’s improved compression over AVC which leads to quicker start times, less buffering and, often, a higher resolution being delivered to the user. AV1 is seen as providing these same benefits over AVC without the patent problems that come with HEVC.

 
It’s not all about resolution, however, points out Paul MacDougall from BitMovin. Resolution can be useful, for instance in animations. For animated content, resolution is worth having because it accentuates the lines which add intelligibility to the picture. For some content, with many similar textures, grass, for instance, then quality through bitrate may be more useful than adding resolution. Vittorio Giovara from Vimeo agrees, pointing out that viewer experience is a combination of many factors. Though it’s trivial to say that a high-resolution screen of unintended black makes for a bad experience, it is a great reminder of things that matter. Less obviously, Vittorio highlights the three pillars of spatial, temporal and spectral quality. Temporal refers to upping the bitrate, spatial is, indeed, the resolution and spectral refers to bit-depth and colour-depth know as HDR and Wide Colour Gamut (WCG).

Nathan Egge from Mozilla acknowledges that in their 2018 code release at NAB, the unoptimized encoder which was claimed by some to be 3000 times slower than HEVC, was ’embarrassing’, but this is the price of developing in the open. The panel discusses the fact that the idea of developing compression is to try out approaches until you find a combination that work well. While you are doing that, it would be a false economy to be constantly optimising. Moreover, Netflix’s Anush Moorthy points out, it’s a different set of skills and, therefore, a different set of people who optimise the algorithms.

Questions fielded by the panel cover whether there are any attempts to put AV1 encoding or decoding into GPU. Power consumption and whether TVs will have hardware or software AV1 decoding. Current in-production AV1 uses and AVC vs VVC (compression benefit Vs. royalty payments).

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Speakers

Vittorio Giovara Vittorio Giovara
Manager, Engineering – Video Technology
Vimeo
Nathan Egge Nathan Egge
Video Codec Engineer,
Mozilla
Paul MacDougall Paul MacDougall
Principal Sales Engineer,
Bitmovin
Anush Moorthy Anush Moorthy
Manager, Video and Image Encoding
Netflix
Tim Siglin Tim Siglin
Founding Executive Director
Help Me Stream, USA

Video: Futuristic Codecs and a Healthy Obsession with Video Startup Time

These next 12 months are going to see 3 new MPEG standards being released. What does this mean for the industry? How useful will they be and when can we start using them? MPEG’s coming to the market with a range of commercial models to show it’s learning from the mistakes of the past so it should be interesting to see the adoption levels in the year after their release. This is part of the second session of the Vienna Video Tech Meetup and delves into startup time for streaming services.

In the first talk, Dr. Christian Feldmann explains the current codec landscape highlighting the ubiquitous AVC (H.264), UHD’s friend, HEVC (H.265), and the newer VP9 & AV1. The latter two differentiate themselves by being free to used and are open, particularly AV1. Whilst slow, both the latter are seeing increasing adoption in streaming, but no one’s suggesting that AVC isn’t still the go-to codec for most online streaming.

Christian then introduces the three new codecs, EVC (Essential Video Coding), LCEVC (Low-Complexity Enhancement Video Coding) and VVC (Versatile Video Coding) all of which have different aims. We start by looking at EVC whose aim is too replicate the encoding efficiency of HEVC, but importantly to produce a royalty-free baseline profile as well as a main profile which improves efficiency further but with royalties. This will be the first time that you’ve been able to use an MPEG codec in this way to eliminate your liability for royalty payments. There is further protection in that if any of the tools is found to have patent problems, it can be individually turned off, the idea being that companies can have more confidence in deploying the new technology.

The next codec in the spotlight is LCEVC which uses an enhancement technique to encode video. The aim of this codec is to enable lower-end hardware to access high resolutions and/or lower bitrates. This can be useful in set-top boxes and for online streaming, but also for non-broadcast applications like small embedded recorders. It can achieve a light improvement in compression over HEVC, but it’s well known that HEVC is very computationally heavy.

LCEVC reduces computational needs by only encoding a lower resolution version (say, SD) of the video in a codec of your choice, whether that be AVC, HEVC or otherwise. The decoder will then decode this and upscale the video back to the original resolution, HD in this example. This would look soft, normally, but LCEVC also sends enhancement data to add back in the edges and detail that would have otherwise been lost. This can be done in CPU whilst the other decoding could be done by the dedicated AVC/HEVC hardware and naturally encoding/decoding a quarter-resolution image is much easier than the full resolution.

Lastly, VVC goes under the spotlight. This is the direct successor to HEVC and is also known as H.266. VVC naturally has the aim of improving compression over HEVC by the traditional 50% target but also has important optimisations for more types of content such as 360 degree video and screen content such as video games.

To finish this first Vienna Video Tech Meetup, Christoph Prager lays out the reasons he thinks that everyone involved in online streaming should obsess about Video Startup Time. After defining that he means the time between pressing play and seeing the first frame of video. The longer that delay, the assumption is that the longer the wait, the more users won’t bother watching. To understand what video streaming should be like, he examines Spotify’s example who have always had the goal of bringing the audio start time down to 200ms. Christophe points to this podcast for more details on what Spotify has done to optimise this metric which includes activating GUI elements before, strictly speaking, they can do anything because the audio still hasn’t loaded. This, however, has an impact of immediacy with perception being half the battle.

“for every additional second of startup delay, an additional 5.8% of your viewership leaves”

Christophe also draws on Akamai’s 2012 white paper which, among other things, investigated how startup time puts viewers off. Christophe also cites research from Snap who found that within 2 seconds, the entirety of the audience for that video would have gone. Snap, of course, to specialise in very short videos, but taken with the right caveats, this could indicate that Akamai’s numbers, if the research was repeated today, may be higher for 2020. Christophe finishes up by looking at the individual components which go towards adding latency to the user experience: Player startup time, DRM load time, Ad load time, Ad tag load time.

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Speakers

Christian Feldmann Dr. Christian Feldmann
Team Lead Encoding,
Bitmovin
Christoph Prager Christoph Prager
Product Manager, Analytics
Bitmovin
Markus Hafellner Markus Hafellner
Product Manager, Encoding
Bitmovin

Video: OTT Fundamentals & hands-on video player lab

Whilst there are plenty of videos explaining the basics streaming, few of them talk you through the basics of actually implementing a video player on your website. The principles taught in this hands-on Bitmovin webinar are transferable to many players, but importantly at the end of this talk you’ll have your own implementation of a video player which you can make in real time using their remix project at glitch.com which allows you to edit code and run it immediately in the browser to see your changes.

Ahead of the tutorial, the talk both explains the basics of compression and OTT led by Kieran Farr, Bitmovin’s VP of marketing and Andrea Fassina, Developer Evangelist. Andrea outlines a simplified OTT architecture where he looks at the ‘ingest’ stage which, in this example, is getting the videos from Instagram either via the API or manually. It then looks at the encoding step which compresses the input further and creates a range of different bitrates. Andrea explains that MPEG standards such as H.264, H.265 are commonly used to do this making the point that MPEG standards typically require royalty payments. This year, we are expecting to see VVC released by MPEG (H.266).

Andrea then explains the relationship between resolution, frame rate and file sizes. Clearly smaller files are better as they require less time to download leading to quicker downloads so faster startup times. Andrea discusses how the resolutions match the display resolutions with TVs having 1920×1080 resolution or 2160×3840 resolution. Given that higher resolutions have more picture detail, there is more information to be sent leading to larger file sizes.

Source: Bitmovin https://bit.ly/2VwStwC

When you come to set up your transcoder and player, there are a number of options you need to set. These are determined by these basics, so before launching into the code, Andrea looks further into the fundamental concepts. He next looks at video compression to explain the ways in which compression is achieved and the compromises within. Andrea starts from the first MJPEG codecs where each frame was its own JPEG image and they simply animated from one JPEG to another to show the video – not unlike animated GIFs used on the internet. However by treating each frame on its own ignores a lot of compression opportunity. When looking at one frame to the next, there are a lot of parts of the image which are the same or very similar. This allowed MPEG to step up their efforts and look across a number of frames to spot the similarities. This is typically referred to as temporal compression as is it uses time as part of the process.

In order to achieve this, MPEG splits all frames into blocks, squares in AVC, which are called macro blocks which be compared between frames. They then have 3 types of frame called ‘I’, ‘P’ and ‘B’ frames. The I frames have a complete description of that frame, similar to a JPEG photograph. P frames don’t have a complete description of the frame, rather they some blocks which have new information and some information saying that ‘this block is the same as this block in this other frame. B frames have no complete new image parts, but create the frame purely out of frames from the recent future and recent past; the B stands for ‘bi-directional’.

Ahead of launching into the code, we then look at the different video codecs available. He talks about AVC (discussed in detail here), HEVC (detailed in this talk) and compares the two. One difference is HEVC uses much more flexible macro block sizes. Whilst this increases computational complexity, it reduces the need to send redundant information so is an important part of the achieving the 50% bitrate reduction that HEVC typically shows over AVC. VP9 and AV1 complete the line-up as Andrea gives an overview of which platforms can support these different codecs.

Source: Bitmovin https://bit.ly/2VwStwC

Andrea then introduces the topic of Adaptive bitrate, ABR. This is vital in the effective delivery of video to the home or mobile phones where bandwidth varies over time. It requires creating several different renditions of your content at various bitrates, resolutions and even frame rate. Whilst these multiple encodes put a computational burden on the transcode stage, it’s not acceptable to allow a viewer’s player to go black, so it’s important to keep the low bitrate version. However there is a lot of work which can go into optimising the number and range of bitrates you choose.

Lastly we look at container formats such as MP4 used in both HLS and MPEG-DASH and is based on the file format ISO BMFF. Streaming MP4 is usually called fragmented MP4 (fMP4) as it is split up into chunks. Similarly MPEG2 Transport Streams (TS files) can be used as a wrapper around video and audio codecs. Andrea explains how the TS file is built up and the video, audio and other data such as captions are multiplexed together.

The last half of the video is the hands-on section during which Andrea talks us through how to implement a video player in realtime on the glitch project allowing you to follow along and do the same edits, seeing the results in your browser as you go. He explains how to create a list of source files, get the player working and styled correctly.

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Download the presentation
Speakers

Kieran Farr Kieran Farr
VP of Marketing,
Bitmovin
Andrea Fassina Andrea Fassina
Developer Evangelist,
Bitmovin