(Pocket-lint) - Mobile HDR is one of the biggest tech advances for mobile devices in recent years. It's something that's been landing on flagship phones since 2017, with most manufacturers, including Apple and Samsung getting in on the act.
It's following a trend that's been tearing through the TV industry over the past few years, but really hit home in the last couple of years. And, more recently, the move to get more content in HDR to your mobile devices has stepped up. It's still relatively early days for this emerging technology, but it's also hugely interesting and worth paying some attention to.
Here's everything you need to know about the latest step in mobile entertainment.
What is HDR?
HDR stands for high dynamic range and it's been a buzzword in TV for the past couple of years. If you've bought a top-tier 4K television recently, it's almost certain that it will also be HDR capable.
HDR means that the display is able to produce a wider range of colours, bringing greater authenticity, but in many cases it is about brightness and contrast.
On televisions, HDR is about using the display's peak brightness to give amazing highlights, while still maintaining fidelity in darker areas of a scene. For example, a typical HDR scene is a sunset, where you have searing oranges across the sky, a detailed shadowed foreground and perhaps the blazing sun dipping over the horizon.
Mobile HDR aims to create the same stunning visuals. In reality, it's about making content look better - specifically movies and games - with increased impact and expanded colours.
What is mobile HDR?
Mobile HDR is specifically about bringing a similar experience from your 4K TV to your smartphone or tablet. Again, it's all about using the skills of the display, giving amazing colours and controlling the backlight to provide better video performance.
It has a great deal to do with brightness, because it's the ability of the display to push the brightness in areas that are supposed to be bright that really makes a difference. Many mobile devices have displays that are under-utilised and HDR can make much better use of the display's ability to show content.
The Samsung Galaxy Note 7 originally attempted to kickstart the mobile HDR movement, but the format's biggest early hitter was the LG G6. It offered HDR10 and Dolby Vision support, just like the company's televisions. It's now common across many flagship and sub-flagship devices.
There are several different standards for HDR on mobile that you'll hear about: there's HDR10, which is a common standard, and there's Dolby Vision, which Dolby is pushing as an enhanced HDR experience. Then there is HDR10+, an advanced version of HDR10 that works much like Dolby Vision and is starting to be more widely adopted by TVs and mobile devices.
Dolby Vision and HDR10+ aim to achieve much the same results as HDR10, but more dynamically. They can use frame-by-frame metadata to ensure that the display you're watching is showing you the best results as the content shifts and changes. HDR10, by comparison, uses metadata less often, once for an entire show for example, so technically isn't as potent a solution. Whether you'll see the difference or not between the two standards on a small screen is debatable.
Dolby Vision on phones is still relatively rare, mainly because content over mobile is more often presented in HDR10, but Apple supports through iTunes on the iPhone 11.
What is Mobile HDR Premium?
In February 2017, the Ultra HD Alliance announced a new standard for mobile devices, called Mobile HDR Premium. The Ultra HD Alliance is made up of movie producers and technology companies looking to establish a standard for next-gen entertainment. The UHDA is best known for the Ultra HD Premium badging that it applies to televisions - as seen on Samsung, LG and other sets.
For mobile devices, the Mobile HDR Premium badging means that the device adheres to a particular standard too, designed to ensure that you're getting a great experience from mobile HDR entertainment.
The specifics include:
- Resolution: 60 pixels/degree
- Dynamic range: .0005-550nits
- Colour space: 90 per cent of P3 colour gamut
- Bit depth: 10
These standards apply to smartphones, tablets and laptop computers, meaning that the Mobile HDR Premium badging could be applied to all those devices which offer HDR content, but not necessarily at 4K resolution.
How does Dolby Vision on mobile work?
The LG G6 was the first mobile device to support Dolby Vision and the message from its implementation on TV has changed slightly. On mobile devices, Dolby Vision is a software solution, rather than hardware-based. On the first run of TVs to support Dolby Vision, you needed the correct hardware to decode the information; but doing a similar job with software alone is something Dolby seems to be accepting as necessary for the proliferation of its standard.
Dolby Vision (or HDR10) doesn't apply to all your content, only the content that's encoded for HDR, like Umbrella Academy on Netflix, for example. Unlike technologies such as Sony's X-Reality image processing that attempts to improve everything you see on your device, Dolby Vision or HDR only swings into action when you're watching the right content.
With this in mind, you can't turn it off or on: it just works, taking the content you're watching and using the metadata to control the backlight of your device to give you the best colour, great contrast and those characteristic dazzling highlights.
You'll find markers in apps like Netflix showing you that something is in HDR. On the iPhone XS, for example, Netflix will show you Stranger Things in Dolby Vision and all you have to do it hit play.
What about variable bitrate services?
One thing that's helped services like Netflix and Amazon Video offer great experiences is the use of variable bitrate. This means that the stream of data is scaled, so on a slow connection you get less data and watch at a lower resolution - without the video stopping or buffering. This also allows almost instant starting of videos too.
We asked Dolby what happened to Dolby Vision content in a variable bitrate situation and the reply was that it very much came down to the content provider. Technically, HDR and resolution aren't intrinsically linked, so you can have that HDR effect even if you're not watching the highest quality stream.
One thing is clear though: you don't want to be jumping from HDR to non-HDR, because the colours will be changing and that doesn't make for a good viewing experience.
What about auto-dimming on your display?
This is something of a potential problem for HDR on mobile devices. The TV in your front room probably doesn't change its brightness as readily as your smartphones. It's likely you set it to your preference and then it stays at that level. However, mobile devices use auto-brightness to change the display to suit the environment - it's darker in dark conditions, brighter in bright conditions.
This will have an impact on how HDR content is displayed. Talking to Dolby, the company confirmed that it takes into account these sorts of hardware factors with the aim of always delivering the best visual experience when watching Dolby Vision content, although the company does have a TV solution to deal with this, called Dolby Vision IQ, something that's not available on mobile devices.
But you can mess with it. If you turn auto-brightness off and turn the display brightness all the way down, then you get a fairly dull result. The long and short of it is that you're best leaving your device on auto-brightness to get the best effect that's balanced for the environment that you're in.
What does mobile HDR content look like?
We've been fortunate enough to see HDR working on several phones in the last couple of years, with Netflix offering HDR on many devices - even Dolby Vision in some cases. Apple's iTunes also offers movies in HDR and Dolby Vision for its compatible devices.
If you've seen HDR content on TV, then you know what to expect: colours are richer, plus better contrast and brighter highlights. HDR makes everything look better and this is certainly an exciting evolution: if you watch Netflix or iTunes content on your tablet or smartphone in bed, it's going to look better.
However, the size of the display means that the effect isn't as profound. While HDR looks better than not-HDR on your mobile device, you don't get that punch-in-your-face wow effect that you will on a huge TV - the bigger screen just makes for a bigger experience.
That said, having watched BT Sport's HDR offering on a smartphone and compared it to an SDR version on the big screen, there's a lot of background detail that comes through. For example, in the case of BT Sport and a football broadcast, there's detail in the stands that you might not get from the SDR version.
What HDR content is available?
In the last few years, there has been a significant rise in the amount of HDR content available. Netflix supports HDR (and Dolby Vision) on mobile devices, however and will tell you what quality level you'll be able to view the show in. The Amazon Video app also supports HDR on Android, but tends to tell you the max quality you'd get on a TV - 4K Dolby Vision - even when your device isn't capable of displaying that, leaving you with HD only.
For Apple users there's the added advantage that iTunes movies are available in Dolby Vision and HDR too. This is really a play to boost Apple TV, but for those watching on the latest Apple devices, you'll benefit there too.
YouTube also offers HDR content and one of the best sources of free HDR content if you don't have access to Netflix, and as we mentioned there are HDR sport features too, from services like BT Sport. In short, there's no lack of HDR content available in 2020.
Can my old phone support mobile HDR?
This is a good question. Technically, if the display is good enough, then there could be some scope to enable viewing of HDR content on existing devices. When talking to Dolby, we were told that Dolby Vision isn't restricted to a specific set of specifications on mobile devices and that the aim was to make the display work to its maximum potential.
As Dolby Vision on mobile devices is a software solution, it's really down to the manufacturer to work with Dolby to enable support. For a manufacturer this is likely to involve licensing fees, so we suspect that some won't take the Dolby path for this reason.
However, with manufacturers wanting to sell you new devices, it's unlikely they will move to support HDR in older devices.