Encoding

Video: Virtues of Recycling in Multi-rate Encoding

Posted on by Russell Trafford-Jones

Recycling may be good for the environment, but it turns out it’s good for bit rate too. Remembering that MPEG (and similar) video compression includes splitting the picture into blocks, decomposing them into basic patterns and also estimating their motion, this talk wonders whether calculations made on the blocks and the motion of these blocks done on the SD picture can be re-used on the HD picture and then again on the UHD picture. If so, this would surely reduce the computation needed.

“The content is perceptually identical,” explains Alex Giladi from Comcast, “…the only difference is how many pixels it occupies.” as he highlights the apparent wastefulness of ABR encoding where the same video is taken in multiple resolutions and encoded independently. The technique starts by analysing the lowest resolution video for motion and re-using the calculations at a higher resolution. Naturally there are aspects which can’t be captured in the lower resolutions, but also there are sensitivities to the bitrate so Alex explains the refinement options which have been developed to adapt to those.

As the talk wraps up, Alex presents the results found which show that the quality is not degraded and there is a better than 2x speed increase. Finally we look at a real-life flow of encoding.

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Speakers

Alex Giladi Alex Giladi
Distinguished Architect,
Comcast

Video: What to do after per-title encoding

Posted on by Russell Trafford-Jones

Per-title encoding is a common method of optimising quality and compression by changing the encoding options on a file-by-file basis. Although some would say the start of per-scene encoding is the death knell for per-title encoding, either is much better than the more traditional plan of applying exactly the same settings to each video.

This talk with Mux’s Nick Chadwick and Ben Dodson looks at what per-title encoding is and how to go about doing it. The initial work involves doing many encodes of the same video and analysing each for quality. This allows you to out which resolutions and bitrates to encode at and how to deliver the best video.

Ben Dodson explains the way they implemented this at Mux using machine learning. This was done by getting computers to ‘watch’ videos and extract metadata. That metadata can then be used to inform the encoding parameters without the computer watching the whole of a new video.

Nick takes some time to explain MUX’s ‘convex hulls’ which give a shape to the content’s performance at different bitrates and helps visualise the optimum encoding parameters the content. Moreover, we see that using this technique, we can explore how to change resolution to create the best encode. This doesn’t always mean reducing the resolution; there are some surprising circumstances when it makes sense to start at high resolutions, even for low bitrates.

The next stage after per-title encoding is to segment the video and encode each segment differently which Nick explores and explains how to deliver different resolutions throughout the stream seamlessly switching between them. Ben takes over and explains how this can be implemented and how to chose the segment boundaries correctly, again, using a machine learning approach to analysis and decision making.

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Speakers

Nick Chadwick Nick Chadwick
Software Engineer,
Mux
Ben Dodson Ben Dodson
Data Scientist,
Mux

Video: The Evolution of Video APIs

Posted on by Russell Trafford-Jones

APIs underpin our modern internet and particularly our online streaming services which all. An API is a way for two different programs or services to communicate with each other; allowing access, sharing locations of videos, providing recommendations etc.

Phil Cluff from Mux, takes a look at the evolution of these APIs, showing the simple ones, the complex and how they have changed as time has gone on, culminating in advice to the APIs writers of today and tomorrow.

Security is a big deal and increasingly is in focus for video companies. Whilst the API itself is usually sent over secure means, the service still needs to authenticate users and the use of DRM needs to be considered. Phil talks about this and ultimately the question comes down to what you are trying to protect and your attack surface.

APIs tend to come in two types, explains Phil, Video Platform vs ‘Encoding’ APIs. Encoding APIs a more than pure encoding APIs, there is transcoding, packaging, file transfer and other features built in to most ‘encoding’ services. Video Platform APIs are typically for a whole platform so also include CDN, Analytics, Cataloguing, playback and much more

In terms of advice, Phil explains that APIs can enable ‘normal’ coders – meaning people who aren’t interested specifically in video – to use video in their programs. This can be done through well thought out APIs which make good decisions behind the scenes and use sensible defaults.

API is so important, asserts Phil, that it should be considered as part of the product so treated with similar care. It should be planned, resourced properly, be created as part of a dialogue with customers and, most importantly, revisited later to be upgraded and improved.

Phil finishes the talk with a number of other pieces of advice and answers questions from the floor.

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Speaker

Phil Cluff Phil Cluff
Streaming Specialist,
Mux

Video: VVC, EVC, LCEVC, WTF? – An update on the next hot codecs from MPEG

Posted on by Russell Trafford-Jones


The next-gen codecs are on their way: VVC, EVC, LCEVC but, given we’re still getting AV1 up and running, why do we need them and when will they be ready?

MPEG are working hard on 3 new video codecs, one in conjunction with the ITU, so Christian Feldmann from Bitmovin is here to explain what each does, the target market, whether it will cost money and when the standard will be finalised.

VVC – Versatile Video Codec – is a fully featured video codec being worked on as a successor to H.265, indeed the ITU call it H.266. MPEG call it MPEG-I Part 3. Christian explains the ways this codec is outperforming its peers including a flexible block partitioning system, motion prediction which can overlap neighbouring macroblocks and triangle prediction to name but three.

EVC is the Essential Video Codec which, intriguingly, offers a baseline which is free to use and a main profile which requires licences. The thinking here is that if you have licensing issues, you have the option of just turning off that feature which could five you extra leverage in patent discussions.

Finally, LCEVC – the Low Complexity Essential Video Codec allows for enhancement layers to be added on top of existing bitstreams. This can allow UHD to be used where only HD was possible before due to being able to share decoding between the ASIC and CPU, for example.

These all have different use cases which Christian explains well, plus he brings some test results along showing the percentage improvement over today’s HEVC encoding.

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Speaker

Christian Feldmann Christian Feldmann
Codec Engineer,
Bitmovin