Shield Transcoding DTS audio

[D34DC3N73R 18]

The Nvidia Shield should be able to direct play this audio, but it is forcing a transcode due to "unsupported audio". For reference, the same file direct plays using Plex. Server version 4.1.0.16 beta, Emby Android TV version 1.6.98g. Please let me know if any other info is required here.

server-log.txt

shield-unsupported audio.txt

[Luke 39648]

Ok, can we look at an example playback session? Please attach the information requested in how to report a media playback issue. thanks !

[D34DC3N73R 18]

server log and the transcode log are attached to the OP am I missing something?

[Luke 39648]

Did you enable the audio downmix option in the app's settings?

[ebr 15576]

What is your outboard audio equipment and how is it connected?

 

The system is not reporting support for DTS audio.

[D34DC3N73R 18]

If I enable downmix to stereo, the video/audio will direct play. However, I'd like to keep the 5.1 channels if possible.

 

The Shield is HDMI to my TV. I use HDMI ARC from the TV to a Polk audio magnifi soundbar. This did get me thinking though, I use passthrough audio in plex, which is maybe why I don't have issues with DTS. Does emby have something similar that could be enabled?

[MRobi 161]

If I enable downmix to stereo, the video/audio will direct play. However, I'd like to keep the 5.1 channels if possible.

 

The Shield is HDMI to my TV. I use HDMI ARC from the TV to a Polk audio magnifi soundbar. This did get me thinking though, I use passthrough audio in plex, which is maybe why I don't have issues with DTS. Does emby have something similar that could be enabled?

From looking at your first image it appears the audio profile is DTS-HD Master Audio. HDMI-ARC does not support DTS-HD, not enough bandwidth available. I may be mistaken but I don't believe the polk soundbars support the newer DTS-HD format either. 

[D34DC3N73R 18]

From looking at your first image it appears the audio profile is DTS-HD Master Audio. HDMI-ARC does not support DTS-HD, not enough bandwidth available. I may be mistaken but I don't believe the polk soundbars support the newer DTS-HD format either. 

 

If I'm not mistaken, DTS-HD MA is backward compatible with DTS capable receivers/soundbars. DTS-HD MA audio should play as DTS. 

 

https://en.wikipedia.org/wiki/DTS-HD_Master_Audio

 

 

According to the DTS-HD White Paper,^[9] DTS-HD Master Audio contains 2 data streams: the original DTS core stream and the additional "residual" stream which contains the "difference" between the original signal and the lossy compression DTS core stream. The audio signal is split into two paths at the input to the encoder. One path goes to the core encoder for backwards compatibility and is then decoded. The other path compares the original audio to the decoded core signal and generates residuals, which are data over and above what the core contains that is needed to restore the original audio as bit-for-bit identical to the original. The residual data is then encoded by a lossless encoder and packed together with the core. The decoding process is simply the reverse.

[MRobi 161]

If I'm not mistaken, DTS-HD MA is backward compatible with DTS capable receivers/soundbars. DTS-HD MA audio should play as DTS. 

 

https://en.wikipedia.org/wiki/DTS-HD_Master_Audio

Yes, it is backwards compatible, but it still needs to be connected in a way that can support the throughput of data. It sends the full signal and then your receiver decodes the information. HDMI-ARC lacks that ability.

 

As a test, you can try plugging your shield directly to your soundbar and seeing if it will play that way. I still suspect you'll get remuxed audio though if the polk doesn't support DTS-HD.

[D34DC3N73R 18]

Yes, it is backwards compatible, but it still needs to be connected in a way that can support the throughput of data. It sends the full signal and then your receiver decodes the information. HDMI-ARC lacks that ability.

 

As a test, you can try plugging your shield directly to your soundbar and seeing if it will play that way. I still suspect you'll get remuxed audio though if the polk doesn't support DTS-HD.

 

Any guesses on how Plex is able to achieve 5.1 playback using the same file without transcoding audio?

 

And further down the wiki page

 

 

DTS-HD Master Audio may be transported to AV receivers in 5.1, 6.1 or 7.1 channels, at lossless quality, in one of three ways depending on player and/or receiver support:^[9]

• Over 6, 7 or 8 RCA connectors as analog audio (not lossless), using the player's internal decoder and digital-to-analog converter (DAC).
• Over HDMI 1.1 (or higher) connections as 6-, 7- or 8-channel linear PCM, using the player's decoder and the AV receiver's DAC.
• Over HDMI 1.3 (or higher) connections as the original DTS-HD Master Audio bitstream, with decoding and DAC both done by the AV receiver.

This seems to suggest it's being sent as linear PCM when using plex.

Edited March 26, 2019 by D34DC3N73R

[ebr 15576]

Plex is transcoding it too they are just doing it in the app.

 

Your setup does not support DTS (of any flavor) so we are converting it to DD so that you get your 5.1 sound.

 

Was there a playback or audio problem?

[D34DC3N73R 18]

Plex is transcoding it too they are just doing it in the app.

 

Your setup does not support DTS (of any flavor) so we are converting it to DD so that you get your 5.1 sound.

 

Was there a playback or audio problem?

 

It's the root cause of this playback issue. If it didn't need to transcode, it would direct play and emby wouldn't have to transcode 4k content (or have that transcoding error). Should emby only be transcoding audio in this circumstance? Because it seems to transcode both audio and video in this case. I'm not quite understanding how my setup doesn't support DTS. The Shield has DTS support, my TV has DTS support, and the soundbar has DTS support. DTS-HD should go to the TV and be backward compatible, thus sending the DTS track to the soundbar.  

 

So my choices currently are: downmix absolutely everything to stereo or transcode serverside (which has its own set of problems)?

[ebr 15576]

Your system, as currently connected/configured, does not support passing through DTS (do you see any DTS options in the playback settings in the app?).  I, like the previous poster, suspect this is due to the ARC not supporting it.

 

According to the ffmpeg log you posted, the only thing being converted is the audio:

  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (dts (dca) -> ac3 (native))

[MRobi 161]

It's the root cause of this playback issue. If it didn't need to transcode, it would direct play and emby wouldn't have to transcode 4k content (or have that transcoding error). Should emby only be transcoding audio in this circumstance? Because it seems to transcode both audio and video in this case. I'm not quite understanding how my setup doesn't support DTS. The Shield has DTS support, my TV has DTS support, and the soundbar has DTS support. DTS-HD should go to the TV and be backward compatible, thus sending the DTS track to the soundbar.  

 

So my choices currently are: downmix absolutely everything to stereo or transcode serverside (which has its own set of problems)?

It doesn't support it because you are hooked up through HDMI-ARC. HDMI-ARC lacks the ability to transfer the full DTS-HD signal. So your soundbar doesn't receive it. Picture trying to push a watermelon through a garden hose. It's too big. The DTS-HD signal is the watermelon, the HDMI-ARC connection is the garden hose.

 

Your setup as it sits goes SHIELD ---> TV ----> Soundbar

Your setup for DTS-HD SHOULD go SHIELD ---> Soundbar ----> TV

 

If you've confirmed your polk soundbar does support DTS-HD, going shield-soundbar-tv is the only way you will be able to make use of that.

 

ARC should be used when you want to use the built-in apps of your smart tv through your soundbar. If you've got a shield, odds are good that any built-in app from your tv can also be added to the shield. If you want to connect more than 1 device to your soundbar (ie: blueray player, cable receiver, etc..) I recommend an HDMI switch instead of using HDMI-ARC.

 

If the newer audio formats are a priority, ARC should not even be in your vocabulary.

[Riggs 303]

https://hometheaterreview.com/everything-you-need-to-know-about-arc-audio-return-channel/

 

 

"Firstly, a little background. HDMI Audio Return Channel (ARC) is based on the IEC 60958-1 specification, which is essentially the S/PDIF audio spec. There's two types of ARC in HDMI; Single Mode and Common Mode, but unfortunately we don't get informed as to which type any given product supports. 

Single Mode ARC uses a single wire in the HDMI link, with performance limited to around 3Mbps. This enables support for 2.0 LPCM and "lossy" compressed surround formats including Dolby Digital and DTS 5.1, but nothing more. Cable length is a huge factor with Single mode, with reliability typically getting flaky beyond about 7-8m in a passive HDMI cable. 

Common Mode ARC is superior, but less common (excusing the pun) in terms of deployment. It's still based on the same S/PDIF spec, but can theoretically support up to around 12Mbps. This is enough to carry 24-bit 192kHz 2-channel audio, or — to the point of this blog — a Dolby format called E-AC-3, which we know better as Dolby Digital Plus. This can also carry Metadata-enhanced Audio Transmission (MAT), being audio objects; aka Atmos.

So existing HDMI ARC can potentially support Dolby Atmos by maxing out the Common mode capability with an MAT stream. But there's a huge catch. Two, actually; 
 

1. Channel count & resolution — while E-AC-3 can support up to 15.1 channels of audio, it's well beyond the HDMI ARC spec. Even getting 7.1 channels to pass is a stretch, so even if the stream contains object metadata, it will lack the resolution and height speakers. 
2. System support — getting Atmos to work through HDMI ARC requires Common mode support in both the TV and AVR, and a high integrity link in-between. Even then, performance will be marginal.

HDMI 2.1 will change things considerably. It introduces enhanced ARC, or eARC for short, which can support up to twelve times the bandwidth of ARC, supporting up to 32 channels of 24-bit 192kHz audio! That is, eARC will support all of the same audio formats upstream as what we can already get in a downstream HDMI link.  

In summary, a basic, lower resolution form of Dolby Atmos may work through existing HDMI ARC, but it is highly system and link dependent. This is why we tend to generalise that ARC doesn't support Atmos, as it's out of spec and can't be relied upon. If you are designing this capability into systems, sticking with proven product combinations and short connectivity can give your systems an edge until eARC comes along and opens up our options." from: http://community.cedia.net/blogs/david-meyer/2018/06/25/dolby-atmos-over-hdmi-arc

Edited March 28, 2019 by HRSCR

[Riggs 303]

Bottom line

Audio Return Channel is convenient and can simplify your setup. However, it might also mean you don't get surround sound, and it definitely means you won't get the high-resolution audio formats from Blu-ray.

So for the best sound quality, it's still recommended to use individual HDMI cables to link to a sound bar or receiver when you can.

[Spaceboy 2565]

Bottom line

 

Audio Return Channel is convenient and can simplify your setup. However, it might also mean you don't get surround sound, and it definitely means you won't get the high-resolution audio formats from Blu-ray.

 

So for the best sound quality, it's still recommended to use individual HDMI cables to link to a sound bar or receiver when you can.

arc works fine for me with a Samsung tv and Yamaha soundbar

[Riggs 303]

arc works fine for me with a Samsung tv and Yamaha soundbar

 

It could be, but the restriction of bandwith is there, is real, ARC is documented (speaking of sound) and not a problem to control devices.

 

The audio return is the problem, not the direct audio.

[Spaceboy 2565]

It could be, but the restriction of bandwith is there, is real, ARC is documented (speaking of sound) and not a problem to control devices.

 

The audio return is the problem, not the direct audio.

yeah I wasn’t being dismissive, I thought it was an interesting observation which I will keep an eye out for. Aren’t there better quality leads that can help or is that just marketing blah?

[ebr 15576]

yeah I wasn’t being dismissive, I thought it was an interesting observation which I will keep an eye out for. Aren’t there better quality leads that can help or is that just marketing blah?

 

That's mostly marketing (assuming you are using a high-bandwidth HDMI cable in the first place).

[Riggs 303]

@@Spaceboy Yeah, some devices work really good

 

@@ebr yes, wire hdcp2.2, marketing etc, etc. 

 

I agree with both of you but is a fact that the return audio is really bad on ARC. i found sites asking for high speed on ARC.  

[D34DC3N73R 18]

I switched to optical but it didn't seem to make a difference. Logs attached Plex does give me DTS options when using passthrough optical. Where would I find DTS settings in the emby app?

ffmpeg-remux-996ac29e-1ea3-4a46-8ca5-cecd28ef62e7_1.txt

[ebr 15576]

An optical connection is just as limited as the ARC.  In fact, that it the same spec the ARC is implementing (SPDIF).

[D34DC3N73R 18]

So I'm gathering emby is just unable to do whatever plex is doing to enable direct play of this same file? My only option is to downmix absolutely every file to stereo within the app if I want direct playback?

[Riggs 303]

So I'm gathering emby is just unable to do whatever plex is doing to enable direct play of this same file? My only option is to downmix absolutely every file to stereo within the app if I want direct playback?

 

Hello.

I think that this topic is being extended by simple things or that is not either well explained or not being understood well.

 

A- Plex decode everything, Emby doesn't.

 

B- Meanwhile Plex report to the user: "okay i'm direct playing the content". That's is not true. Again... Plex, decode everything.

 

Did you remember when some no stereo radio stations sent a hack signal to show the red light in your stereo receiver and was a monoaural signal? Is the same thing.

 

I used Plex for a long time and even a month ago I was using it on my computer when I was running Windows 10 on the server. When I switched to Linux I decided not to install Plex, because the truth is that the amount of space that Plex uses is gigantic in GB. My main disk is an M2 SSD of just 256GB. I preferred to use that space for something more productive than Plex.

Having said that, and after testing Plex on different devices and with different configurations in my house for several years. I decided to stay with Emby because Plex, frankly, is in decline. The best thing that Plex currently have is its marketing.

 

We have to check your setup.

 

Having said that, I offer to help you, I am not here to bother you.

 

I need to start:

1-The brand and model of your soundbar.

2-The brand and model of your TV.

3-The type of HDMI cables you are using (if you know the brand and the model, better)

4- I need the diagram of your setup (wires and direction). Even if you need to draw on a sheet of paper at hand the diagram of your connection setup and then take a picture with your phone.

 

Regards