Yesterday the Blu-ray Disc Association formally completed the Ultra HD Blu-ray specification. The specification has been under development for some time, with the first information about it being released in September of last year. The new specification allows for higher resolutions, a greater range of colors, and larger capacity disks in order to store a new generation of Ultra HD content.

The biggest point of the new Ultra HD Blu-ray specification lies in its name. Ultra HD Blu-ray will support the 3840x2160 Ultra HD resolution that has become standard across so called "4K" or Ultra HD televisions. That being said, an increase in resolution is not the only important part of the Ultra HD Blu-ray spec. The Ultra HD content standard, more accurately known as BT.2020, defines various aspects that go beyond resolution, including color gamut, color bit depth, and frame rate.

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In my view, the most important aspect of the BT. 2020 standard is the use of the Rec. 2020 color gamut. The color gamut that has been used for basically all picture and video content for quite some time now is called Rec. 709 or sRGB. sRGB is actually quite a narrow gamut, and has an lower overall number of colors than even the NTSC (1953) gamut that was used for video content before it. The Ultra HD specification uses the much larger Rec. 2020 color gamut, which will allow for colors of greater saturation to be reproduced. You can see this in the image above, with sRGB being the smaller triangle, and Rec. 2020 being the larger triangle that surrounds it.

In order to support the larger Rec. 2020 color gamut without introducing color banding, a higher bit depth is required. This is because a greater number of discrete colors will be required to display gradations that span a greater range of saturations. Ultra HD Blu-ray supports 10bit per channel color depth for content that uses Rec. 2020 for its color encoding. This moves the number of possible colors that can be displayed from approximately 16.7 million to 1.07 billion. I think it would have been better to use 10bit color for sRGB content and 12bit color for Rec. 2020 content, as current 8bit sRGB content can already experience noticeable color banding, but it looks like the additional space and hardware support required have not been deemed worth it.

While the new Ultra HD Blu-ray standard supports the existing 50GB capacity for Blu-ray disks, there will be disks of greater capacity for content that requires higher bitrates. 50GB disks will have video encoded at up to 82Mbps, while 66GB disks can support up to 108Mbps, and 100GB disks support 128Mbps. In order to encode videos with these high resolutions, bitrates, and greater color depth, Ultra HD Blu-ray will make use of HEVC video encoding.

While the appeal of physical media such as Blu-ray is in decline due to the rise of streaming media, it's still the go-to for users who care about having the highest possible visual quality. It will definitely take time for Ultra HD Blu-ray to be adopted in the market, and possibly longer for Ultra HD TVs that actually support the Rec. 2020 color space. It will be interesting to see where the market for movies and TV shows moves in the future, and what position physical media will be in at that time.

Source: Blu-ray Association (via Tech Report)

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  • nathanddrews - Thursday, May 14, 2015 - link

    Audio won't improve much more than it currently has. We already have access to the lossless (and sometimes uncompressed) audio sources used in the theater. Current Blu-ray discs already come with Dolby Atmos - you just need a newer AVR that can process the flags, otherwise you just hear the "normal" 5.1/7.1 stream.

    Probably my favorite part about these new object-based audio mixes (specifically DTSX) is the ability to control object volume instead of channel volume. So if you want to increase the volume of the score and turn down everything else, you can. If you want to turn up the dialog so you can hear it over 'splosions, you can. Of course, it's unlikely that we'll be given too much freedom over that since sound engineers usually take great pride in their mixes.
  • phoenix_rizzen - Thursday, May 14, 2015 - link

    Being able to turn up the dialog and/or turn down the rest would be a welcome improvement to many movies out there. Too many times I find myself holding the remote and cranking up the audio to hear dialog, cranking down the audio during action, rinse and repeat.

    If that works well, it would be worth investing in a new audio setup.
  • Murloc - Thursday, May 14, 2015 - link

    that's because you're not doing reference listening like the technicians meant you to.
    If you want the cinema experience, you will get cinema volume dynamic range.
    You're not meant to crank it down when there are explosions.

    Anyway current AVRs can already do dynamic compression if you want to listen at low volumes, it has different names depending on the brand.
  • DanNeely - Saturday, May 16, 2015 - link

    Room shaking explosions might be fun in the cinema itself (YMMMV); but if you're trying to watch a movie at home while someone else is sleeping, or in an apartment building with poor sound proofing standard linear volume controls are inadequate. Doubly so if one of the people watching is hard of hearing and needs to turn the volume up above normal levels to hear the dialog at all.
  • DanNeely - Wednesday, May 13, 2015 - link

    For anyone curious how rec 2020 compares with the Adobe RGB standard that's been common on wide gamut monitors over the last few years, Rec 2020 is about as large of an increase over it as aRBG was over sRGB.
  • Laststop311 - Wednesday, May 13, 2015 - link

    So all these early 4k adopters cant even display all the colors no rec 2020 support on current 4k tv's. I'm glad I got a 1080 lg oled instead of 4k. Need 10bit lcd screens with wide color gamut backlight or 10 bit oled that can support wide gamut before its worth buying a 4k tv.
  • Rishi100 - Wednesday, May 13, 2015 - link

    It's great. I hope now, contents should be moved to 500gb usb 3 hard disk with all the additional material and appropriate copy protection for ultra HD.
  • A5 - Thursday, May 14, 2015 - link

    My Blu-Rays don't lose data when I drop them, so no thanks.
  • DCide - Thursday, May 14, 2015 - link

    So do they expect a 50GB Ultra HD Blu-ray to take more or less time to encode than a current 50GB Blu-ray?

    On the surface the answer would seem obvious, but there's so much difference in codecs that the time and processing power required can vary widely.
  • psychobriggsy - Thursday, May 14, 2015 - link

    HEVC is considerably more compute intensive for encoding (decently) than H.264, so yes, encoding into these formats would be bad.

    OTOH decoding HEVC is not more compute intensive, so transcoding to a lower resolution from HEVC to H.264 should still be viable. OTOH the savings might not be worth it...

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