Video

Video: Colour

Posted on by Russell Trafford-Jones

With the advent of digital video, the people in the middle of the broadcast chain have little do to with colour for the most part. Yet those in post production, acquisition and decoding/display are finding it life more and more difficult as we continue to expand colour gamut and deliver on new displays.

Google’s Steven Robertson takes us comprehensively though the challenges of colour from the fundamentals of sight to the intricacies of dealing with REC 601, 709, BT 2020, HDR, YUV transforms and all the mistakes people make in between.

An approachable talk which gives a great overview, raises good points and goes into detail where necessary.

An interesting point of view is that colour subsampling should die. After all, we’re now at a point where we could feed an encoded with 4:4:4 video and get it to compress the colour channels more than the luminance channel. Steven says that this would generate more accurate colour than by stripping it of a fixed amount of data like 4:2:2 subsampling does.

Given at Brightcove HQ as part of the San Francisco Video Tech meet-ups.

Watch now!

Speaker

Steven Robertson Steven Robertson
Software Engineer,
Google

Video: Using PTP & SMPTE 2059 A Practical Experience Perspective

Posted on by Russell Trafford-Jones

NAB 2019 saw another IP Showcase with plenty of talks on the topic on many people’s minds: PTP and timing in IP systems. It seems there’s a lot which needs to be considered and, truth be told, a lot of people don’t feel they have the complete list of questions to be asking and certainly don’t know all the answers.

So, here, Greg Shay from Telos talks about the learnings from his extensive experience with timing IP signals and with PTP under SMPTE 2059. He hits the following topics;

  • Must you always have a GPS reference for the PTP master?
  • Are PTP-aware switches always necessary?
  • Can you safely not use PTP Peer Delay requests / responses?
  • What is the effect of internal oscillator tolerance and stability when designing PTP client equipment?

To my ears, these are 4 well placed questions because I’ve heard these asked; they are current in the minds of people who are grappling with current and prospective IP installations.

Greg treats gives each one of these due time and we see some interesting facts come out:
You don’t always need a time-synchronised PTP master (pretending to be in 1970 can work just fine).
Compensating for PTP Peer Delay can make things worse – which seems counter-intuitive to the point of PTP Peer Delay requests.
We also see why PTP-aware switches matter and a statistical method of managing without.

This is a talk which exemplifies IP talks which ‘go deeper’ than simply explaining the point of standards. Implementation always takes thought – not only in basic architecture but in use-cases and edge-cases. Here we learn about both.

Watch now!

Speakers

Greg Shay Greg Shay
CTO,
The Telos Alliance

Video: ABR Streaming and CDN Performance

Posted on by Russell Trafford-Jones

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

Watch the video now!

Speaker

Yuriy Reznik Yuriy Reznik
VP, Research
Brightcove

Video: Adaptive Bitrate Algorithms: How They Work

Posted on by Russell Trafford-Jones

Streaming on the net relies on delivering video at a bandwidth you can handle. Called ‘Adaptive Bitrate’ or ABR, it’s hardly possible to think of streaming without it. While the idea might seem simple initially – just send several versions of your video – it quickly gets nuanced.

Streaming experts Streamroot take us through how ABR works at Streaming Media East from 2016. While the talk is a few years old, the facts are still the same so this remains a useful talk which not only introduces the topic but goes into detail on how to implement ABR.

The most common streaming format is HLS which relies on the player downloading the video in sections – small files – each representing around 3 to 10 seconds of video. For HLS and similar technologies, the idea is simply to allow the player, when it’s time to download the next part of the video, to choose from a selection of files each with the same video content but each at a different bitrate.

Allowing a player to choose which chunk it downloads means it can adapt to changing network conditions but does imply that each file has contain exactly the same frames of video else there would be a jump when the next file is played. So we have met our first complication. Furthermore, each encoded stream needs to be segmented in the same way and in MPEG, where you can only cut files on I-frame boundaries, it means the encoders need to synchronise their GOP structure giving us our second complication.

These difficulties, many more and Streamroot’s solutions are presented by Erica Beavers and Nikolay Rodionov including experiments and proofs of concept they have carried out to demonstrate the efficacy.

Watch now!

Speakers

Erica Beavers Erica Beavers
Head of Marketing & Partnerships,
Streamroot
Nikolay Rodionov Nikolay Rodionov
Co-Founder, CPO
Streamroot