Video: WAVE (Web Application Video Ecosystem) Update

With wide membership including Apple, Comcast, Google, Disney, Bitmovin, Akamai and many others, the WAVE interoperability effort is tackling the difficulties web media encoding, playback and platform issues utilising global standards.

John Simmons from Microsoft takes us through the history of WAVE, looking at the changes in the industry since 2008 and WAVE’s involvement. CMAF represents an important milestone in technology recently which is entwined with WAVE’s activity backed by over 60 major companies.

The WAVE Content Specification is derived from the ISO/IEC standard, “Common media application format (CMAF) for segmented media”. CMAF is the container for the audio, video and other content. It’s not a protocol like DASH, HLS or RTMP, rather it’s more like an MPEG 2 transport stream. CMAF nowadays has a lot of interest in it due to its ability to delivery very low latency streaming of less than 4 seconds, but it’s also important because it represents a standardisation of fMP4 (fragmented MP4) practices.

The idea of standardising on CMAF allows for media profiles to be defined which specify how to encapsulate certain codecs (AV1, HEVC etc.) into the stream. Given it’s a published specification, other vendors will be able to inter-operate. Proof of the value of the WAVE project are the 3 amendments that John mentions issued from MPEG on the CMAF standard which have come directly from WAVE’s work in validating user requirements.

Whilst defining streaming is important in terms of helping in-cloud vendors work together and in allowing broadcasters to more easily build systems, its vital the decoder devices are on board too, and much work goes into the decoder-device side of things.

On top of having to deal with encoding and distribution, WAVE also specifies an HTML5 APIs interoperability with the aim of defining baseline web APIs to support media web apps and creating guidelines for media web app developers.

This talk was given at the Seattle Video Tech meetup.

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John Simmons John Simmons
Media Platform Architect,

Video: Bandwidth Prediction in Low-Latency Chunked Streaming

How can we overcome one of the last, big, problems in making CMAF generally available: making ABR work properly.

ABR, Adaptive Bitrate is a technique which allows a video player to choose what bitrate video to download from a menu of several options. Typically, the highest bitrate will have the highest quality and/or resolution, with the smallest files being low resolution.

The reason a player needs to have the flexibility to choose the bitrate of the video is mainly due to changing network conditions. If someone else on your network starts watching some video, this may mean you can no longer download video quick enough to keep watching in full quality HD and you may need to switch down. If they stop, then you want your player to switch up again to make the most of the bitrate available.

Traditionally this is done fairly simply by measuring how long each chunk of the video takes to download. Simply put, if you download a file, it will come to you as quickly as it can. So measuring how long each video chunk takes to get to you gives you an idea of how much bandwidth is available; if it arrives very slowly, you know you are close to running out of bandwidth. But in low-latency streaming, your are receiving video as quickly as it is produced so it’s very hard to see any difference in download times and this breaks the ABR estimation.

Making ABR work for low-latency is the topic covered by Ali in this talk at Mile High Video 2019 where he presents some of the findings from his recently published paper which he co-authored with, among others, Bitmovin’s Christian Timmerer and which won the DASH-IF Excellence in DASH award.

He starts by explaining how players currently behave with low-latency ABR showing how they miss out on changing to higher/lower renditions. Then he looks at the differences on the server and for the player between non-low-latency and low-latency streams. This lays the foundation to discuss ACTE – ABR for Chunked Transfer Encoding.

ACTE is a method of analysing bandwidth with the assumption that some chunks will be delivered as fast as the network allows and some won’t be. The trick is detecting which chunks actually show the network speed and Ali explains how this is done and shows the results of their evaluation.

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Ali C. Begen Ali C. Begen
Technical Consultant and
Computer Science Professor

Video: Optimizing ABR Encode, Compute & Control for Performance & Quality

Adaptive bitrate, ABR, is vital in effective delivery of video to the home where bandwidth varies over time. It requires creating several different renditions of your content at various bitrates, resolutions and even frame rate. These multiple encodes put a computational burden on the transcode stage.

Lowell Winger explains ways of optimising ABR encodes to reduce the computation needed to create these different versions. He explains ways to use encoding decisions from one version and use them in other encodes. This has a benefit of being able to use decisions made on high-resolution versions – which are benefiting from high definition to inform the decision in detail – on low-resolution content where the decision would otherwise be made with a lot less information.

This talk is the type of deep dive into encoding techniques that you would expect from the Video Engineering Summit which happens at Streaming Media East.

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Lowell Winger Lowell Winger
Former Senior Director of Engineering,
IDT Inc.

Video: ABR Streaming and CDN Performance

Hot on the heel’s of yesterday’s video all about Adaptive Bitrate (ABR) streaming we have research engineer Yuriy Reznik from Brightcove looking at the subject in detail. We outlined the use of ABR yesterday showing how it is fundamental to online streaming.

Brightcove, an online video hosting platform with its own video player, has a lot of experience of delivery over the CDN. We saw yesterday the principles that the player, and to an extent the server, can use to deal with changing network (and to an extent changing client CPU usage) by going up and down through the ABR ladder. However this talk focusses on how the CDN in the middle complicates matters as it tries its best to get the right chunks in the right place at the right time.

How often are there ‘cache misses’ where the right file isn’t already in place? And how can you predict what’s necessary?

Yuriy even goes in to detail about how to work out when HEVC deployment makes sense for you. After all, even if you do deploy HEVC – do you need to do it for all assets? And if you do only deploy for some assets, how do you know which? Also, when does it make sense to deploy CMAF? In this talk, we hear the answers.

The slides for this talk

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Yuriy Reznik Yuriy Reznik
VP, Research