Questions about Audio Formats, Passthrough and Conversion on Rasberry Pi

novalis · June 29, 2019 at 9:47 AM

I would like to know how LE handles the different audio formats. First of all here are my settings :

Code

LibreELEC (official): 9.0.2 (RPi2.arm)
KODI-TV:~ # cat /storage/.kodi/userdata/guisettings.xml | grep passthrough     
<setting id="audiooutput.ac3passthrough" default="true">true</setting>     
<setting id="audiooutput.dtshdpassthrough" default="true">false</setting>     
<setting id="audiooutput.dtspassthrough">true</setting>     
<setting id="audiooutput.eac3passthrough" default="true">false</setting>     
<setting id="audiooutput.passthrough">true</setting>     
<setting id="audiooutput.passthroughdevice">PI:HDMI</setting>     
<setting id="audiooutput.truehdpassthrough" default="true">false</setting>

AVR is a Denon X4000, capable of all formats known nowadays. 5.1 Setup.

Above EAC3 aka DD+ passthrough is set to false because it won't play. Without passthrough it is passed as PCM (AVR shows Multi Channel In), same for Dolby TrueHD. DTS HD Master shows up as DTS Sourround.

Is this all as expected and normal for audio playback on Rasberry?

As you can read from the settings truehdpassthrough and dtshdpassthrough are set to false and it does not appear in the Settings tab, so there is probably a reason for that too. Probably RasPi is not able to handle that high bitrates? But then why is DTS HD MA recognized as DTS Sourround by the AVR and not as Multi Channel In (PCM) like the Dolby Formats?

**DaVu** · July 1, 2019 at 6:38 PM Official Post

Quote from novalis

capable of all formats known nowadays

currently not Atmos capable. Just to mention the formats which are "known nowadays". And there won't be an update for it.

Quote from novalis

same for Dolby TrueHD. DTS HD Master shows up as DTS Sourround.

Yes, the RPi can't handle bitstreaming of HD audio formats. To have the benefit of DTS-HDMA you have to use PCM where Kodi will decode the audio and send it via 8ch-PCM (over HDMI) to the AVR. The AVR will then show "Multichannel". That's expected. Simply use that. I doubt that you will hear the difference anyway as there's none.

Quote from novalis

As you can read from the settings truehdpassthrough and dtshdpassthrough are set to false and it does not appear in the Settings tab

because the RPi is not capable of.

Quote from novalis

But then why is DTS HD MA recognized as DTS Sourround by the AVR and not as Multi Channel In (PCM) like the Dolby Formats?

If you play a track containing DTS-HDMA, Kodi will show that in its video OSD. But as the RPi isn't capable of bitstreaming HD audio you will only get the Core of those tracks.

Let's assume you play DTS-HDMA or DTS-HRA. The core of both is "DTS" and that's what you get. The same counts for DolbyTrueHD where you will only get DolbyDigital from your RPi.

If you want more, either get better hardware or use PCM.

The RPi is only capable of bitstreaming DolbyDigital and DTS. That might bring up the question to DD+ again, which I can't answer for sure. But others have already answered in your other thread and confirmed it working.

If you don't get any of them and only see "Multichannel" on your AVR, then simply disable "Sync Playback to display" as that will disable passthrough even if that's enabled in your settings.

novalis · July 1, 2019 at 6:59 PM

Very helpfull indeed, thanks.

I can live with PCM but would prefer the passthrough, just to let the AVR do its job and show the format.

"Sync Playback to display" is not enabled in my seetings.

**DaVu** · July 1, 2019 at 7:44 PM Official Post

Yeah, and if you want to have all the benefit of bitstreaming, then I have to say that the RPi3 is not the correct dievice for you. For me it's not the correct device as well as I also like bitstreaming, hence I own something x86. The actual RPi4 should do bitstreaming of HD audio. But that's currently a pretty new product and many tests have to be done. So if you want something that "just works", I can't recommend that.

novalis · July 1, 2019 at 7:55 PM

I have ordered a Raspi 4 already and yes I am prepared to wait for Kodi Matrix.

I'm looking forward to a 35 Watt HTPC with HDMI 2.1 onboard graphics. Still waiting...

**DaVu** · July 1, 2019 at 9:00 PM Official Post

I guess you won't have a real benefit of HDMI 2.1. We discussed the stuff which is supported by HDMI 2.1 and for the normal usage and by looking at your setup, I would say you don't need to wait for that. 35W would be nice, indeed.

HDMI 2.0b supports 4k60 and unless you need more resolution (where we currently have no content for) or higher fps (your eye is not capable of recognizing nearly anyything >100Hz, IIRC) I don't see the benefit.

The only interesting option is EARC if Netflix supports Atmos and you will use that with your TV app and would like to have that at your AVR.

But as your AVR isn't capable of atmos at all, I also don't see the benefit in buying something with HDMI 2.1

Did I miss something?

novalis · July 1, 2019 at 10:57 PM

AVR gets replaced too. Thinking of HDR10+ and Dolby Vision somewhere in the future. I know it is possible with 2.0 but want to be on the secure side. Don't really care about the sound side so much. I don't plan on more than 5.1 in my living room.