Dolby Vision

[pxr5]

Dolby Vision is a PITA. It looks amazing of course, but the implementation for end users by Dolby is poor IMO. Firstly it needs to be licenced and not free (unlike HDR10). Dolby don't give out much information either and the technicalities seem vague (https://professionalsupport.dolby.com/s/article/What-is-Dolby-Vision-Profile?language=en_US). The use of profiles is complex and confusing. I've been fiddling with video encoding since the days of DivX and XviD and I have a basic grip on the techniques and tools required to manipulate video/audio but DV is a different beast altogether. Regarding the profiles - basically Dolby Vision builds layers on top of an existing HDR10 layer adjusting the picture based on a per-shot or even per-frame basis (unlike HDR10 which is fixed throughout). The main 4 DV profiles in use today are:

Profile 5 Single layer, Dolby Vision-only support
Profile 7 Dual layer (Base Layer + Enhancement Layer) Can have Full Enhancement Layer (FEL) or Minimum Enhancement Layer (MEL) - for Ultra HD Blu-ray
Profile 8.1 HDR10 + Dolby Vision compatibility
Profile 8.2 SDR compatibility

There are more profiles than this, but see how complex it all is. So, basically playing back DV can be very problematic. Incorrect playback support (hw and sw) can cause numerous issues - e.g. purple/green playback on Dolby Vision Profile 5 is a common issue. This leaves consumers confused about which playback device/software is the best to use. Kodi has only just implemented a way (frig) of on-the-fly transcoding of DV Profile 7 to the more compatible Profile 8, but in doing so is removing the Full Enhancement Layer (FEL). Or, I think even worse, is falling back to HDR10 just to get playback working without any DV. Even media analysis is difficult with DV. The most common tool, Mediainfo, can't even output the full information about DV, especially profile 7 (which is effectively an HDR10 stream with a 1080p FEL layer sat on top to adjust the picture). The only way of doing so is with MakeMKV or BDinfo - not ideal. Furthermore DV has become such an issue that the guys at the Jellyfin Forums have come with a way of converting DV to HDR10 by removing all DV layer information from the stream - it's such an issue to some (https://forum.jellyfin.org/t-converting-dolby-vision-to-hdr10).

UHD Bluray players can, of course, playback DV correctly from disk but to stream such video whilst maintaining the full DV is almost impossible. Yet there is a glimmer of hope as there are 2 devices that can play DV Profile 7 correctly (there are actually some older OLED TVs that can too and certain BR players) - https://docs.google.com/spreadsheets/d/15i0a84uiBtWiHZ5CXZZ7wygLFXwYOd84/edit?gid=845372636#gid=845372636. They are the UGOOS AM6b+ and the Minix U22-XJ Max as they have the necessary hardware AMLogic chips; but not in their as-purchased state as Android Players. Instead the clever guys at Corelec have somehow managed to create a Corelec OS (based on Kodi) that fully utilises the hardware to allow playback of full DV - https://discourse.coreelec.org/t/guide-s922x-j-ugoos-am6b-coreelec-installation-and-faqs/51231.

So, the point of this long-winded post (God I'm a geek sometimes lol) is that I've found and ordered a used Minix U22-XJ Max to give all this a try and then, maybe, I can watch full UHD remuxes/BDs properly at last - these https://www.reddit.com/r/CoreElecOS/comments/1j3lgw2/list_of_dolby_vision_p7fel_films/

[pxr5]

Right, the Minix U22-XJ Max has arrived - second hand from CEX for £75, which a lot better than the UGOOS AM6b+ costing £199 from the UK or £150 from China. I quickly tested it on the TV in the conservatory and it boots to Android just fine. It's too bright in there to carry on, but I've prepped a USB stick with the latest nightly Coreelec already.

[pxr5]

Got round to trying this out at last after being away for some time. With a prepped USB stick installed, the Minix U22X-J Max booted into Corelec just fine - even the remote worked perfectly (a separate remote.conf file needs creating for applicable remotes). Of course the CE OS is almost the same as Kodi Omega 21.2, but with a couple of additional menus for CE.

I then moved the box to the living room and installed on to our main TV. I'm so familiar with Kodi that I had the whole lot set up (libraries, skins, video and audio configuration, regional etc,) in 30 minutes or so. It played HDR and Dolby Vision just as well as my other devices, but this new box is for those pesky DV Profile 7 FEL videos.

I grabbed some DV test videos which all played perfectly and as can be seen in the images below the play back was spot on. I tried the same 2 videos on a Fire TV Stick 4 Max Gen2 and only a blank red screen is shown as that device (as virtually all other devices) can not play the DV Profile 7 Full Enhancement Layer. The same happened with the other test videos I tried. So, success.

Highslide Image Viewer

Highslide Image Viewer

Highslide Image Viewer

Of course the point of all this is to get the optimal picture quality. I've tried a couple of 4K UHD remuxes that contain the Full Enhancement Layer and testing against the same video played on the Firestick (and directly on my TV) I do see some clear differences and as good as the original BR as played on my Panasonic UHD player, so happy days.

Next things to do:

1. Coreelec will boot and run fine from a USB stick or SD card, but for speed and integrity of data it's better to get it running from internal memory. It's easy to do: just SSH into the Minix box running CE and enter a simple command (once done, one can still reboot to the original android OS). I'm going to test for a while yet before committing to doing this though.

2. This has caused some conflict in the CE community - but there is branch from CE called the CM build which gives a lot more options for Dolby Vision settings, even converting HDR10 to DV on the fly and some other funky stuff. This CM build also needs a specific (modified) Kodi skin for it to work correctly. Again, I may try this in the future after I've tested for a bit longer.

[pxr5]

More DV pain to come:

https://news.dolby.com/en-WW/253671-dolby-unveils-dolby-vision-2-a-new-era-for-tv-picture-quality/

[pxr5]

More Dolby shenanigans. Dolby Atmos this time. Dolby Atmos really comes in 2 flavours: Dolby Digital Plus+Atmos (streaming) and Dolby TrueHD+Atmos (Blu ray). The former being lossy and the latter lossless. I've not researched this much but I'm having problems with TrueHD not being passed by my TV over eArc (it results in the TruHD+Atmos being down converted to Dolby Digital); I can play directly from my UHD BR player, but that's not much use for streamed content. Some Blu rays include both formats (and DTS stuff) and that's great when ripping to mkv - to keep all the possible audio streams. Some newer ones don't though and it's TrueHD+Atmos only. Of course the obvious thing is convert from TrueHD+Atmos to DDP+Atmos. But as this is Dolby nothing is that simple. A bit of googling initially led me to believe that this is impossible, but then I discovered a post on Reddit pointing me to this https://community.firecore.com/t/help-get-more-dolby-atmos-on-apple-tv/16477/1303.

So it is doable and I followed the quite simple guide. Download deezy.exe - check, download ffmpeg.exe - check, download truehdd.exe - check, download DEE 5.2.1 - er, nope. Dolby Encoding Engine (DEE) is available from Dolby, but not for us minions sadly. People must be doing this as the guide wouldn't exist otherwise. More fiddling and googling and eventually came across a useable DEE here https://github.com/MaitreAnonyme/Maitre-Dolby. After that hurdle it was just a matter of getting the mkv, stripping all audio except TrueHD+Atmos and running deezy as per the guide. This resulted with a separate DDP+Atmos file (EAC3) which I then muxed back into the original mkv. Worked fine. It's a bit of a ball ache tbh but achievable at least for those awkward instances.

[pxr5]

Dolby Atmos issues again. I've got a copy of Steven Wilson's new remaster of Gentle Giant's The Power and the Glory - now in Dolby Atmos. As a Matroska Audio ('mka') file it's designed to be streamed so it was surprising to find it only has a Dolby TrueHD+Atmos stream within. Using the tricks mentioned above I created a Dolby Digital Plus+Atmos 'EAC' file and muxed it back into the original mka file. I now have the choice to pick either Atmos stream during playback and both work perfectly with the embedded chapters and images.