Video: 5 Myths About Dolby Vision & HDR debunked

There seem no let up in the number of technologies coming to market and whilst some, like HDR, have been slowly advancing on us for many years, the technologies that enable them such as Dolby Vision, HDR10+ and the metadata handling technologies further upstream are more recent. So it’s no surprise that there is some confusion over what’s possible and what’s not.

In this video, Bitmovin and Dolby the truth behind 5 myths surrounding the implementation and financial impact of Dolby Vision and HDR in general. Bitmovin sets the scene by with Sean McCarthy giving an overview on their research into the market. He explains why quality remains important, simply put to either keep up with competitors or be a differentiator. Sean then gives an overview of the ‘better pixels’ principle underlining that improving the pixels themselves is often more effective than higher resolution, technologies such as wide colour gamut (WCG) and HDR.

David Brooks then explains why HDR looks better, explaining the biology and psychology behind the effect as well as the technology itself. The trick with HDR is that there are no extra brightness values for the pixels, rather the brightness of each pixel is mapped onto a larger range. It’s this mapping which is the strength of the technology, altering the mapping gives different results, ultimately allowing you to run SDR and HDR workflows in parallel. David explains how HDR can be mapped down to low-brightness displays,

The last half of this video is dedicated to the myths. Each myth has several slides of explanation, for instance, the one suggests that the workflows are very complex. Hangen Last walks through a number of scenarios showing how dual (or even three-way) workflows can be achieved. The other myths, and the questions at the end, talk about resolution, licensing cost, metadata, managing dual SDR/HDR assets and live workflows with Dolby Vision.

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Speakers

David Brooks David Brooks
Senior Director, Professional Solutions,
Dolby Laboratories
Hagan Last Hagan Last
Technology Manager, Content Distribution,
Dolby Laboratories
Sean McCarthy Sean McCarthy
Senior Technical Product Marketing Manager,
Bitmovin
Kieran Farr Moderator: Kieran Farr
VP Marketing,
Bitmovin

Video: Hybrid SDI/ST 2110 Workflows

It’s no secret that SDI is still the way to go for some new installations. For all the valid interest in SMPTE’s ST 2110, the cost savings are only realised either on a large scale or in the case that a system needs continuous flexibility (such as an OB truck) or scalability in the future. Those installations which have gone IP still have some SDI lying around somewhere. Currently, there are few situations where there is an absolute ‘no SDI’ policy because there are few business cases which can afford it.

Looking at the current deployments of broadcast 2110, we have large, often public, broadcasters who are undergoing a tech refresh for a building and can’t justify such as massive investment in SDI or they are aiming to achieve specific savings such as Discovery’s Eurosport Transformation Project which is an inspirational, international project to do remote production for whole buildings. We also have OB trucks who benefit significantly from reduced cabling, higher density routing and flexibility. For a more detailed view on 2110 in trucks, watch this video from NEP. In these scenarios, there is nearly always SDI still involved. Some equipment doesn’t yet work fully in 2110, some doesn’t yet work at all and while there are IP versions of some products, the freelance community still needs to learn how to use the new products or work in the new workflows. If you have a big enough project, you’ll hit the ‘vendor not yet ready’ problem, if you have an OB-truck or similar, you are likely to have to deal with the freelance experience issue. Both are reducing, but are still real and need to be dealt with.

Kevin Salvidge from Leader joins the VSF’s Wes Simpson to share his experience of these SDI/IP mixed workflows, many of which are in OB trucks so also include mixed HDR workflows. He starts by talking about PTP and GPS discussing how timing needs to be synced between locations. He then takes a closer look at the job of the camera shaders who make sure all the cameras have the same colour, exposure etc. Kevin talks about how live production in HDR and SDR work touching on the problem of ‘immediacy’. Shaders need to swap between cameras quickly and are used to the immediate switch that SDI can provide. IP can’t offer quite the same immediacy, Kevin says that some providers have added delays into the SDI switches to match the IP switch times within the same truck. This helps set expectations and stop operators pressing two or more times to get a switch made.

Kevin finishes his talk on the topic of synchronising analogue timing signals with PTP. Kevin shows us the different tools you can use to monitor these signals such as a display of PTP timing against B&B timing, a BMCA data readout of data from the PTP grandmasters to check if the BMCA algorithm is working correctly, PTP delay time, packet inter-arrival time, path delay, traffic shaping monitoring. He then closes with a Q&A talking about the continued prevalence of SDI, what ‘eye patterns’ are in the IP world and increasing HDR roll-outs.

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Speaker

Kevin Slavidge
European Regional Development Manager
Leader Europe Ltd.
Wes Simpson Moderator: Wes Simpson
President, Telcom Product Consulting
Owner, LearnIPVideo.com

Video: Banding Impairment Detection

It’s one of the most common visual artefacts affecting both video and images. The scourge of the beautiful sunset and the enemy of natural skin tones, banding is very noticeable as it’s not seen in nature. Banding happens when there is not enough bit depth to allow for a smooth gradient of colour or brightness which leads to strips of one shade and an abrupt change to a strip of the next, clearly different, shade.

In this Video Tech talk, SSIMWAVE’s Dr. Hojat Yeganeh explains what can be done to reduce or eliminate banding. He starts by explaining how banding is created during compression, where the quantiser has reduced the accuracy of otherwise unique pixels to very similar numbers leaving them looking the same.

Dr. Hojat explains why we see these edges so clearly. By both looking at how contrast is defined but also by referencing Dolby’s famous graph showing contrast steps against luminance where they plotted 10-bit HDR against 12-bit HDR and show that the 12-bit PQ image is always below the ‘Barten limit’ which is the threshold beyond which no contrast steps are visible. It shows that a 10-bit HDR image is always susceptible to showing quantised, i.e. banded, steps.

Why do we deliver 10-bit HDR video if it can still show banding? This is because in real footage, camera noise and film grain serve to break up the bands. Dr. Hojat explains that this random noise amounts to ‘dithering’. Well known in both audio and video, when you add random noise which changes over time, humans stop being able to see the bands. TV manufacturers also apply dithering to the picture before showing which can further break up banding, at the cost of more noise on the image.

How can you automatically detect banding? We hear that typical metrics like VMAF and SSIM aren’t usefully sensitive to banding. SSIMWAVE’s SSIMPLUS metric, on the other hand, has been created to also be able to create a banding detection map which helps with the automatic identification of banding.

The video finishes with questions including when banding is part of artistic intention, types of metrics not identifiable by typical metrics, consumer display limitations among others.

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Speakers

Dr. Hojat Yeganeh Dr. Hojat Yeganeh
Senior Member Technical Staff,
SSIMWAVE Inc.

Video: Broadcast Fundamentals: High Dynamic Range

Update: Unfortunately CVP choose to take down this video within 12 hours of this article going live. But there’s good news if you’re interested in HDR. Firstly, you can find the outline and some of the basics of the talk explained below. Secondly, at The Broadcast Knowledge there are plenty of talks discussing HDR! Here’s hoping CVP bring the video back.

Why is High Dynamic Range is like getting a giraffe on a tube train? HDR continues its ascent. Super Bowl LIV was filmed in HDR this year, Sky in the UK has launched HDR and many of the big streaming services support it including Disney+, Prime and Netflix. So as it slowly takes its place, we look at what it is and how it’s achieved in the camera and in production.

Neil Thompson, an Sony Independent Certified Expert, takes a seat in the CVP Common Room to lead us through HDR from the start and explain how giraffes are part of the equation. Dynamic Range makes up two thirds of HDR, so he starts by explaining what it is with an analogy to audio. When you turn up the speakers so they start to distort, that’s the top of your range. The bottom is silence – or rather what you can hear over the quiet hiss that all audio systems have. Similarly in cameras, you can have bright pixels which are a different brightness to the next which represents the top of your range, and the dithering blacks which are the bottom of your range. In video, if you go too bright, all pixels become white even if the subject’s brightness varies which the equivalent of the audio distortion.

With the basic explanation out of the way, Neil moves on to describing the amount or size of dynamic range (DR) which can be done either in stops, contrast ratio or signal to noise ratio. He compares ‘stops’ to a bucket of water with some sludge at the bottom where the range is between the top of sludge and the rim of the bucket. One stop, he explains, is a halving of the range. With the bucket analogy, if you can go half way down the bucket and still hit clear water, you have 1 stop of dynamic range. If you can then go a quarter down with clean water, you have 2 stops. By the time you get to 1/32nd you have 5 stops. If going to 1/64 of the height of the bucket means you end up in the sludge, your system has 5 stops of dynamic range. Reducing the sludge so there’s clear water at 1/64th the height, which in cameras means reducing the noise in the blacks, is one way of increasing the dynamic range of your acquisition.

Update: Unfortunately CVP choose to take down this video within 12 hours of this article going live. But there’s good news if you’re interested in HDR. Firstly, you can find the outline and some of the basics of the talk explained below. Secondly, at The Broadcast Knowledge there are plenty of talks discussing HDR! Here’s hoping CVP bring the video back.

If you would like to know how lenses fit into the equation of gathering light, check out this talk from Cannon’s Larry Thorpe.

Neil looks next at the range of light that we see in real life from sunlight to looking at the stars at night. Our eye has 14 stops of range, though with our iris, we can see the equivalent of 24 stops. Similarly, cameras use an iris to regulate the light incoming which helps move the restricted dynamic range of the camera into the right range of brightness for our shot.

Of course, once you have gathered the light, you need to display it again. Displays’ ability to produce light is measured in ‘nits’, which is the amount of light per metre squared. Knowing how many nits a displays helps you understand the brightness it can show with 1000 nits, currently, being a typical HDR display. Of course, dynamic range is as much about the blacks as the brightness. OLED screens are fantastic at having low blacks, though their brightness can be quite low. LEDs, conversely, Neil explains, can go very bright but the blacks do suffer. You have to also take into account the location of a display device to understand what range it needs. In a dim gallery you can spend longer caring about the blacks, but many places are so bright, the top end is much more important than the blacks.

With the acquisition side explained, Neil moves on to transmission of HDR and it’s like getting a giraffe on a tube train. Neil relates the already familiar ‘log profiles’. There are two HDR curves, known as transfer functions, PQ from Dolby and HLG (Hybrig Log Gamma). Neil looks at which profiles are best for each part of the production workflow and then explains how PQ differs from HLG in terms of expressing brightness levels. In HLG, the brightest part of the signal tells the display device to output as brightly as it can. A PQ signal, however, reserves the brightest signal for 10,000 nits – far higher than displays available today. This means that we need to do some work to deal with the situation where your display isn’t as bright as the one used to master the signal. Neil discusses how we do that with metadata.

Finishing off the talk, Neil takes questions from the audience, but also walks through a long list of questions he brought along including discussing ‘how bright is too bright?’, what to look for in an engineering monitor, lighting for HDR and costs.

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Speakers

Neil Thompson Neil Thompson
Freelance Engineer & Trainer