OTT Archives – Page 9 of 45 – The Broadcast Knowledge

Video: Layer 4 in the CDN

Posted on 19th October 2020 by Russell Trafford-Jones

Caching is a critical element of the streaming video delivery infrastructure, but with the proliferation of streaming services, managing caching is complex and problematic. Open Caching is an initiative by the Streaming Video Alliance to bring this under control allowing ISPs and service providers a standard way to operate.

By caching objects as close to the viewer as possible, you can reduce round-trip times which helps reduce latency and can improve playback but, more importantly, moving the point at which content is distributed closer to the customer allows you to reduce your bandwidth costs, and create a more efficient delivery chain.

This video sees Disney Streaming Services, ViaSat and Stackpath discussing Open Caching with Jason Thibeault, Executive Director of the Streaming Video Alliance. Eric Klein from Disney explains that one driver for Open Caching is from content producers which find it hard to scale, to deliver content in a consistent manner across many different networks. Standardising the interfaces will help remove this barrier of scale. Alongside a drive from content producers, are the needs of the network operators who are interested in moving caching on to their network which reduces the back and forth traffic and can help cope with peaks.

Dan Newman from Viasat builds on these points looking at the edge storage project. This is a project to move caching to the edge of the networks which is an extension of the original open caching concept. The idea stretches to putting caching directly into the home. One use of this, he explains, can be used to cache UHD content which otherwise would be too big to be downloaded down lower bandwidth links.

Josh Chesarek from StackPath says that their interest in being involved in the Open Caching initiative is to get consistency and interoperability between CDNs. The Open Caching group is looking at creating these standard APIs for capacity, configuration etc. Also, Eric underlines the interest in interoperability by the close work they are doing with the IETF to find better standards on which to base their work.

Looking at the test results, the average bitrate increases by 10% when using open caching, but also a 20-40% improvement in connection use rebuffer ratio which shows viewers are seeing an improved experience. Viasat have used multicast ABR plus open caching. This shows there’s certainly promise behind the work that’s ongoing. The panel finishes by looking towards what’s next in terms of the project and CDN optimisation.

Watch now!
Speakers

	Eric Klein Director, CDN Technology, Disney+
	Dan Newman Product Manager, Viasat
	Josh Chesarek VP, Sales Engineering & Support Stackpath.com
	Jason Thibeault Executive Director, Streaming Video Alliance

Video: Optimal Design of Encoding Profiles for Web Streaming

Posted on 14th October 2020 by Russell Trafford-Jones

With us since 1998, ABR (Adaptive Bitrate) has been allowing streaming players to select a stream appropriate for their computer and bandwidth. But in this video, we hear that over 20 years on, we’re still developing ways to understand and optimise the performance of ABRs for delivery, finding the best balance of size and quality.

Brightcove’s Yuriy Reznik takes us deep into the theory, but start at the basics of what ABR is and why we. use it. He covers how it delivers a whole series os separate streams at different resolutions and bitrates. Whilst that works well, he quickly starts to show the downsides of ‘static’ ABR profiles. These are where a provider decides that all assets will be encoded at the same set bitrate of 6 or 7 bitrates even though some titles such as cartoons will require less bandwidth than sports programmes. This is where per-title and other encoding techniques come in.

Netflix coined the term ‘per-title encoding’ which has since been called content-aware encoding. This takes in to consideration the content itself when determining the bitrate to encode at. Using automatic processes to determine objective quality of a sample encode, it is able to determine the optimum bitrate.

Content & network-aware encoding takes into account the network delivery as part of the optimisation as well as the quality of the final video itself. It’s able to estimate the likelihood of a stream being selected for playback based upon its bitrate. The trick is combining these two factors simultaneously to find the optimum bitrate vs quality.

The last element to add in order to make this ABR optimisation as realistic as practical is to take into account the way people actually view the content. Looking at a real example from the US open, we see how on PCs, the viewing window can be many different sizes and you can calculate the probability of the different sizes being used. Furthermore we know there is some intelligence in the players where they won’t take in a stream with a resolution which is much bigger than the browser viewport.

Yuriy brings starts the final section of his talk by explaining that he brought in another quality metric from Westerink & Roufs which allows him to estimate how people see video which has been encoded at a certain resolution which is then scaled to a fixed interim resolution for decoding and then to the correct size for the browser windows.

The result of adding in this further check shows that fewer points on the ladder tend to be better, giving an overall higher quality value. Going much beyond 3 is typically not useful for the website. Shows only a few resolutions needed to get good average quality. Adding more isn’t so useful.

Yuriy finishes by introducing SSIM modeling of the noise of an encoder at different bitrates. Bringing together all of these factors, modelled as equations, allows him to suggest optimal ABR ladders.

Watch now!
Speaker

Yuriy Reznik
Technology Fellow and Head of Research,
Brightcove

Video: Scaling of Live Streaming on the Ingest Side

Posted on 13th October 2020 by Russell Trafford-Jones

You can quickly and easily ‘scale up’ in the cloud, but how? Life is seldom as easy as just clicking a button and the times you do find a button, chances are that will help you scale your outputs. But what happens when you need to scale your inputs? What should you consider when creating your scaling architecture in the cloud? Why is scaling down more difficult than scaling up for a peak? This webinar highlights what you need to know.

Karel Boek from Raskenlund starts by explaining that, while CDNs allow scaling for delivery to end-users, there are fewer solutions for scaling up your ingest. Even if you’re streaming using WebRTC, which isn’t cacheable via CDNs, there are companies such as NanoCosmos who will scale that for you. But for ingest, scaling gets more bespoke more quickly.

There is, Karel explains, the option to outsource entire operation to AWS. For many, this is on the face of it, ideal as there’s not that much work to be done. However, you may need to use more customisation than is possible on this general service and, more importantly, there’s a reason which also affects the second option: creating some of your own workflows but using the cloud to scale.

The problem with cloud autoscalers is that they’re built for HTTP. Karel details how they look at metrics from your servers to determine the point at which they need to be scaled. These could be metrics such as the number of HTTP connections, CPU usage, bandwidth etc. Although Google does allow custom metrics, you may quickly find that a key metric such as GPU load isn’t supported leaving you having to scale without the most important data driving the decision making. Worse, when it comes to scaling down, autoscalers don’t understand ingest. As ingest streams stop, the scaler could be looking at a server which is taking a feed but has very low utilisation and therefore gets killed distributing the stream.

Building your own system is the only way to fully mitigate or remove these problems as you’re putting yourself in full control of creating a system sensitive to the ‘unusual’ metrics of ingesting streams which are very different from serving HTTP files that many autoscalers are built around. Karel looks at the elements of scaling a solution including load balancers, proxy servers and creating an algorithm which listens to metrics and makes up- and down-scaling decisions.

Karel advises writing down the logic for when and how to scale up so that’s it’s clear and well thought-through. Similarly, you need a strategy for Load balancing (i.e. why is round-robin the right/wrong choice for you?) and a scaling down plan. In order to scale down with minimal impact, you need to scale up well. You should use as many clues as you can to group similar feeds onto similar servers. This means a whole server is more likely to be free than if you mix and match long-lived and short-lived feeds on the same server, say.

Finally, Karel details the three main Pitfalls: Scaling down, time taken to scale up (can you wait 3 minutes?), and creating upper limits on your scaling to prevent your algorithm autoscaling you into debt by spinning up tens, hundreds or thousands of unnecessary servers.

Watch now!
Speakers

Karel Boek
CEO,
Raskenlund

Video: CMAF And The Future Of OTT

Posted on 12th October 2020 by Russell Trafford-Jones

Why is CMAF still ‘the future’ of OTT? Published in 2018, CMAF’s been around for a while now so what are the challenges and hurdles holding up implementation? Are there reasons not to use it at all? CMAF is a way of encoding and packaging media which then can be sent using MPEG DASH and HLS, the latter being the path Disney+ has chosen, for instance.

This panel from Streaming Media West Connect, moderated by Jan Ozer, discusses CMAF use within Akami, Netflix, Disney+, and Hulu. Peter Chave from Akamai starts off making the point that CMAF is important to CDNs because if companies are able to use just one CMAF file as the source for different delivery formats, this reduces storage costs for consumers and makes each individual file more popular thus increasing the chance of having a file available in the CDN (particularly at the edge) and reducing cache misses. They’ve had to do some work to ensure that CMAF is carried throughout the CDN efficiently and ensuring the manifests are correctly checked.

Disney+, explains Bill Zurat, is 100% HLS CMAF. Benefiting from the long experience of the Disney Streaming Services teams (formerly BAMTECH), but also from setting up a new service, Disney were able to bring in CMAF from the start. There are issues ensuring end-device support, but as part of the launch, a number were sunsetted which didn’t have the requirements necessary to support either the protocol or the DRM needed.

Hulu is an aggregator so they have strong motivation to normalise inputs, we hear from Hulu’s Nick Brookins. But they also originate programming along with live streaming so CMAF has an important to play on the way in and the way out. Hulu dynamically regenerates their manifests so can iterate as they roll out easily. They are currently part the way through the rollout and will achieve full CMAF compatibility within the next 18 months.

The conversation turns to DRM. CMAF supports two methods of DRM known as CTR (adopted by Apple) and CBC (also known as CBCS) which has been adopted by others. AV1 supports both, but the recommendation has been to use CBC which appears have been universally followed to date explains Netflix’s Cyril Concolato. Netflix have been using AV1 since it was finalised and are aiming to have most titles transitioned by 2021 to CMAF.

Peter comments from Akamai’s position that they see a number of customers who, like Disney+ and Peacock, have been able to enter the market recently and move straight into CMAF, but there is a whole continuum of companies who are restricted by their workflows and viewer’s devices in moving to CMAF.

Low latency streaming is one topic which invigorates minds and debates for many in the industry. Netflix, being purely video on demand, they are not interested in low-latency streaming. However, Hulu is as is Disney Streaming Services, but Bill cautions us on rushing to the bottom in terms of latency. Quality of experience is improved with extra latency both in terms of reduced rebuffering and, in some cases, picture quality. Much of Disney Streaming Services’ output needs to match cable, rather than meeting over-the-air latencies or less.

The panel session finishes with a quick-fire round of questions from Jan and the audience covering codec strategy, whether their workflows have changed to incorporate CMAF, just-in-time vs static packaging, and what customers get out of CMAF.

Watch now!
Speakers

	Cyril Concolato Senior Software Engineer, Netflix
	Peter Chave Principal Architect, Akamai
	Nick Brookins VP, Platform Services Group, Hulu
	Bill Zurat VP, Core Technology Disney Streaming Services
	Moderator: Jan Ozer Contributing Editor, Streaming Media Owner, StreamingLearningCenter.com

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