Clarification on correct AAC 5.1 audio settings

[timfolk]

I tried to play an video with a rare (for me) AAC 5.1 audio stream and got no audio. Vim3 is connected via HDMI to a Denon AVR.

My usual setting was:

• Audio Decoder:
  Alsa: AML-Augesound, HDMI
  Number of channels:
  7.1

• Passthrough Output Device:
  Alsa: AML-Augesound, HDMI

With these settings Kodi plays AAC 2.0 as DD without any issues, but would not play sound with AAC 5.1.

I read these links and found two ways that allow sound with AAC 5.1

How to make AAC sound play? (with bitstream)

Hi I got Coreelec 19.4 on Mecool KI PRO and Coreelec 19.5 rc2 on Tanix TX3. Both work great with movie files with DTS, DTS-MA, DTS-X,DD, DDPlus (Atmos), Dolby-TrueHD, Atmos). I 'm bitstreamin all sound to my Anthem receiver, all types of streams are enabled in hardware> sound section. I have some small size movie files with AAC sound, no matter 2.0, 5.1 or 7.1, but when playing the there is no sound, its not recognized by amplfier. I know we can’t bitstream AAC to amp but how to make it work?…

https://wiki.coreelec.org/coreelec:audio#supported_audio_formats_for_passthrough

Option 1:
*Keep Alsa: AML-Augesound, HDMI
*Change channel count to 2.0 which reveals an Enable DD transcoding option.

Once checked the AAC 5.1 plays as DD - but does it play as 5.1?

Option 2 (noted on the Wiki):
*On Audio Decoder, keep the actual channel count and change Audio Decoder to
Alsa: AML-Augesound, HDMI Multi Channel PCM.

Then AAC 5.1 plays fine (shows ‘Multi Ch In’ on AVR).

95% of the content I play is with the different DD and DTS variations via passthrough, so my question whether I can keep option 2 as default, or is there any need/reason to change the Audio Decoder setting back to from HDMI Multi Channel PCM to just HDMI?

[Joe_90]

Most AVRs will not handle bitstreamed AAC sound, so you need to convert it to PCM or encode it to some Dolby or DTS variant that the AVR can process.

Option 2 from the Wiki is the best option I find. I have a lot of multichannel audio files from my SACD and DVD-Audio discs and they are streamed over HDMI as LPCM to my AVR just fine. Video files with Dolby and DTS soundtracks just passthrough to the AVR where they are internally converted. AAC soundtracks are converted by Kodi to PCM.

[timfolk]

Thank you!

[rmkjr]

For option 2, should you set the channel count to your actual speaker layout, or leave Kodi at 7.1 and let your AVR handle the downmix as needed (running a 5.1 setup myself)?

[Joe_90]

I set the channel count to 5.1 as that is what my speaker layout is. It handles 7.1 properly - left surround and left rear surround are mixed together on left surround and the same for right side.

[rabaraf]

Another type of issue: movie with AAC 2.0.
My current settings in Kodi is Option 2.
Audio stereo mp3 is correctly “trigger” LF and RF loudspeakers only but for the movie with AAC 2.0 I hear all 5.1 loudspeakers.
What configuration should be in Kodi or in AVR Denon to get the output 2.0 instead of 5.1 for the movie?

[rmkjr]

Make sure your AVR is set to Direct, Pure Direct, or Stereo. The surround options would attempt to up convert.

[rabaraf]

Right,
Yellow button “Pure” in Sound Mode section on the bottom of Denon remote
When selected Direct it’s now correct.
Completely forget about this setting.
Thank you very much.

[Joe_90]

Yes - any of the Dolby/DTS matrix type surround audio settings will cause 2.0 audio data play as multichannel if you have a 5.1 (or higher) speaker setup.

[rabaraf]

Not true.
DTS or DTS-HD 5.1 with 5.1 number of channels in Settings - Audio in Kodi gives DTS or DTS-HD 5.1 audio output on 5.1 speakers. There is no “translation” to multichannel PCM.

[Joe_90]

Didn’t mention 5.1. I said 2.0 audio will play as multichannel when you use Dolby/DTS matrix setting on AVR. Nothing to do with Kodi.

[rabaraf]

Yes, this is the setting on Denon Remote I used and the result I wanted to change.