4k HDR Atmos support in mkv files
#1
Hi everyone

Is kodi working on nvidia shield tv able to decode 4k hdr atmos/dts x in mkv files and stream it to my receiver and then my 65c7v oled ?

I know some devecies have problem with mkv and atmos. My tv can decode atmos but hdmi arc is limited to 6 chanels.

I am trying to find device capable of handle it all.

Please is there somebody owning shield tv and kodi able to say its possible ?

Thanks for any reply Smile
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#2
To clarify a few points: if Atmos is decoded anywhere but a soundbar/receiver, you are left with only the 7.1 core (no object metadata). Therefore, you want Atmos tracks to be bitstreamed (also known as passthrough) from the Shield to your receiver or soundbar. Kodi on the Shield does this flawlessly as long as you set your Kodi audio preferences to bitstream TrueHD tracks.

HDMI-ARC isn't exactly limited to six channels. When you're bitstreaming audio, the only thing that matters is bandwidth. HDMI-ARC doesn't have the bandwidth to bitstream TrueHD or uncompressed 7.1, but you CAN bitstream Dolby Digital Plus (eAC3), which is a supported format for Atmos. This is how internal streaming apps pass Atmos to your sound system—by using a lossy format with object metadata.

If you have Atmos tracks in MKV files, it's a near-certainty they're encoded in TrueHD; therefore, as long as you connect the Shield to your receiver/soundbar and then that to the TV you should have no problems! I can personally verify that I had Atmos working on my Shield before I got rid of it for a better device.

HDR is a whole other can of worms on the Shield, since the Shield does not automatically switch between color spaces (Rec.709 for SDR, BT.2020 for HDR) and Nvidia implemented an incorrect algorithm to map Rec.709 colors into BT.2020. So make sure you manually change the color space on the Shield before playing SDR or HDR content.
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#3
@narenh
Maybe you can help me set my nvidia shield tv 2017 correctly, since you got it working?

I'm not getting ATMOS from Kodi but Plex sends ATMOS correctly.
Shield hdmi/arc input to LG tv. Just using built-in speaker for testing because it has the tv display the "atmos" popup when it's received.

In system/audio, I've got allow passthrough & number of channels 7.1

Am I missing a setting?
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#4
You are missing a debug log (wiki)
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#5
(2018-01-20, 02:45)narenh Wrote: To clarify a few points: if Atmos is decoded anywhere but a soundbar/receiver, you are left with only the 7.1 core (no object metadata). Therefore, you want Atmos tracks to be bitstreamed (also known as passthrough) from the Shield to your receiver or soundbar. Kodi on the Shield does this flawlessly as long as you set your Kodi audio preferences to bitstream TrueHD tracks.

HDMI-ARC isn't exactly limited to six channels. When you're bitstreaming audio, the only thing that matters is bandwidth. HDMI-ARC doesn't have the bandwidth to bitstream TrueHD or uncompressed 7.1, but you CAN bitstream Dolby Digital Plus (eAC3), which is a supported format for Atmos. This is how internal streaming apps pass Atmos to your sound system—by using a lossy format with object metadata.

If you have Atmos tracks in MKV files, it's a near-certainty they're encoded in TrueHD; therefore, as long as you connect the Shield to your receiver/soundbar and then that to the TV you should have no problems! I can personally verify that I had Atmos working on my Shield before I got rid of it for a better device.

HDR is a whole other can of worms on the Shield, since the Shield does not automatically switch between color spaces (Rec.709 for SDR, BT.2020 for HDR) and Nvidia implemented an incorrect algorithm to map Rec.709 colors into BT.2020. So make sure you manually change the color space on the Shield before playing SDR or HDR content.
 Thank you for that useful information - you mentioned that you got rid of the Shield for a better device. May I ask what devise you got to replace the Shield ?

Any idea if NVIDIA sorted out the HDR colour mapping and colour space selection issue ?
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#6
You should have TrueHD checked in Kodi.
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#7
I use a MINIX U9-H running LibreELEC instead of the Shield now. The GUI isn't as snappy as the Shield but all content plays back perfectly.

Re: Shield's color space issue, the answer is yes and no (but mostly no). Here's the problem: Android apps still can't *switch* color spaces on-the-fly. But very few, if any, TVs can actually display the full BT.2020 color space. So when you set the Shield to BT.2020, it (correctly) tone maps the output to what your TV can display. This is all well and good for HDR videos, but the tone-mapping compresses the range of all values in the color space (presumably not linearly but still) including those in the Rec.709 space. Therefore, the Shield is outputting wide color tone-mapped to your TVs capabilities when it doesn't really have to—your TV can absolutely display all of Rec.709 completely unadjusted. Nvidia seems to have improved their tone-mapping algorithm to improve this somewhat, but no matter how much it's improved, there are no APIs to tell the system if the content is 709 or 2020, meaning 709 content will always be needlessly tone-mapped.

LibreELEC gets around this by actually changing the video output when you start/end playback. 709/SDR content isn't tone-mapped at all, and 2020/HDR content is tone-mapped at the hardware level to match your display's capabilities.
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