[slowpoke115]

Hi guys, I've looked at a lot of older threads and can only conclude that I'm either doing something wrong or there's some kind of problem with my source files. My apologies if this has been asked in the past with a perfect solution and explanation!

I have a pioneer LX87 and an intel NUC, this is connected via HDMI and I have a 7.1 setup and I'm running Kodi 18.2-LEIA. I've played around with the passthrough settings; irrespective of whether I leave everything switched off/on (or ac3 settings specifically switched off) I'm never able to playback AAC 2 channel audio (this seems to be the standard for all trailers unfortunately). No problems at all playing back any other audio (although I suspect AAC 5.1 wouldn't playback either). Settings initially copied from here: https://kodi.wiki/view/Audio_quickstart_guide. Quite often I'll be unable to play a trailer but the actual movie will playback flawlessly (the video of the trailer plays but the amp remains sat with "stereo" across the screen in silence).

Happy to provide more information if necessary.

Thanks.

[noggin]

Very few amps have AAC decode (it's more common in Japan I believe, and AFAIK AAC passthrough isn't currently supported in Kodi) - so you will want AAC 2.0 and AAC 5.1/7.1 decoded to PCM 2.0 and PCM 5.1/7.1 for HDMI output.  By default if you configure Kodi for 5.1 or 7.1 output in 'Number of Channels' and you have selected the right audio output device (you don't say if you are running Windows or Linux - and if Linux, what bistro) then irrespective of passthrough/bitstream settings, your content SHOULD be decoded to 2.0/5.1/7.1 and output in PCM multichannel.  

UK Freeview HD DVB-T2 TV uses AAC 2.0/AAC 5.1 for broadcast TV (not AC3 - unlike most other countries) and I have no major issues with 2.0/5.1 PCM multichannel output from both ARM and Intel platforms (though I run LibreElec Linux not Windows on most of my Intel platforms. For Windows you may need to chose a WASAPI or DirectSound HDMI device as your output device and also make sure you have configured your speaker layout for your chosen HDMI audio device correctly in Windows sound control panel?)

The other option is to transcode 5.1/7.1 AAC to 5.1 Dolby Digital/AC3.  For this you need to configure 'Number of Channels' to be 2.0 (I know this is counterintuitive) and then you will see a 'Transcode to AC3/Dolby Digital' option appear in your passthrough settings. This will transcode PCM, FLAC, AAC etc. multichannel content to Dolby Digital.  However there should be no reason for you to do that with a modern AVR and Intel NUC, multichannel should just work.

Personally I'd set 'Number of channels to 5.1' and then disable all passthrough settings initially - which will mean DD/AC3, DTS, Dolby True HD, DTS HD MA/HRA, AAC, FLAC, PCM etc. multichannel audio should all be output in 5.1 or 7.1 PCM. That will then tell you whether 5.1/7.1 HDMI multichannel PCM is working. If it isn't then you troubleshoot that before introducing any Passthrough/bitstream for DD/DTS/HD Audio etc.

[slowpoke115]

Very few amps have AAC decode (it's more common in Japan I believe, and AFAIK AAC passthrough isn't currently supported in Kodi) - so you will want AAC 2.0 and AAC 5.1/7.1 decoded to PCM 2.0 and PCM 5.1/7.1 for HDMI output.  By default if you configure Kodi for 5.1 or 7.1 output in 'Number of Channels' and you have selected the right audio output device (you don't say if you are running Windows or Linux - and if Linux, what bistro) then irrespective of passthrough/bitstream settings, your content SHOULD be decoded to 2.0/5.1/7.1 and output in PCM multichannel.  

UK Freeview HD DVB-T2 TV uses AAC 2.0/AAC 5.1 for broadcast TV (not AC3 - unlike most other countries) and I have no major issues with 2.0/5.1 PCM multichannel output from both ARM and Intel platforms (though I run LibreElec Linux not Windows on most of my Intel platforms. For Windows you may need to chose a WASAPI or DirectSound HDMI device as your output device and also make sure you have configured your speaker layout for your chosen HDMI audio device correctly in Windows sound control panel?)

The other option is to transcode 5.1/7.1 AAC to 5.1 Dolby Digital/AC3.  For this you need to configure 'Number of Channels' to be 2.0 (I know this is counterintuitive) and then you will see a 'Transcode to AC3/Dolby Digital' option appear in your passthrough settings. This will transcode PCM, FLAC, AAC etc. multichannel content to Dolby Digital.  However there should be no reason for you to do that with a modern AVR and Intel NUC, multichannel should just work.

Personally I'd set 'Number of channels to 5.1' and then disable all passthrough settings initially - which will mean DD/AC3, DTS, Dolby True HD, DTS HD MA/HRA, AAC, FLAC, PCM etc. multichannel audio should all be output in 5.1 or 7.1 PCM. That will then tell you whether 5.1/7.1 HDMI multichannel PCM is working. If it isn't then you troubleshoot that before introducing any Passthrough/bitstream for DD/DTS/HD Audio etc.

What a perfect reply, thanks! I'm also running libreelec - setup as 5.1 best match.

Table of the outcomes below:

Speaker config	Passthrough on	Passthrough off
5.1	5.1 plays without any issue. AAC does no play and amp does not show any signs of decoding (speaker LED's usually light when sound is passed).	Amp shows PCM, all speaker channels for 5.1 are lit however there is no sound at all. AAC shows no signs of decoding (no speakers lit).
2.0	All settings switched on EXCEPT transcoding resulted in audio for 5.1 streams but AAC still not playing and no sign of decoding.	Obviously no sound at all and no suggestion of it being decoded; this includes both AAC stereo and 5.1.

Any clues on other things to try? Seems AAC is basically impossible.

[noggin]

Very few amps have AAC decode (it's more common in Japan I believe, and AFAIK AAC passthrough isn't currently supported in Kodi) - so you will want AAC 2.0 and AAC 5.1/7.1 decoded to PCM 2.0 and PCM 5.1/7.1 for HDMI output.  By default if you configure Kodi for 5.1 or 7.1 output in 'Number of Channels' and you have selected the right audio output device (you don't say if you are running Windows or Linux - and if Linux, what bistro) then irrespective of passthrough/bitstream settings, your content SHOULD be decoded to 2.0/5.1/7.1 and output in PCM multichannel.  

UK Freeview HD DVB-T2 TV uses AAC 2.0/AAC 5.1 for broadcast TV (not AC3 - unlike most other countries) and I have no major issues with 2.0/5.1 PCM multichannel output from both ARM and Intel platforms (though I run LibreElec Linux not Windows on most of my Intel platforms. For Windows you may need to chose a WASAPI or DirectSound HDMI device as your output device and also make sure you have configured your speaker layout for your chosen HDMI audio device correctly in Windows sound control panel?)

The other option is to transcode 5.1/7.1 AAC to 5.1 Dolby Digital/AC3.  For this you need to configure 'Number of Channels' to be 2.0 (I know this is counterintuitive) and then you will see a 'Transcode to AC3/Dolby Digital' option appear in your passthrough settings. This will transcode PCM, FLAC, AAC etc. multichannel content to Dolby Digital.  However there should be no reason for you to do that with a modern AVR and Intel NUC, multichannel should just work.

Personally I'd set 'Number of channels to 5.1' and then disable all passthrough settings initially - which will mean DD/AC3, DTS, Dolby True HD, DTS HD MA/HRA, AAC, FLAC, PCM etc. multichannel audio should all be output in 5.1 or 7.1 PCM. That will then tell you whether 5.1/7.1 HDMI multichannel PCM is working. If it isn't then you troubleshoot that before introducing any Passthrough/bitstream for DD/DTS/HD Audio etc.

What a perfect reply, thanks! I'm also running libreelec - setup as 5.1 best match.

Table of the outcomes below:

Speaker config	Passthrough on	Passthrough off
5.1	5.1 plays without any issue. AAC does no play and amp does not show any signs of decoding (speaker LED's usually light when sound is passed).	Amp shows PCM, all speaker channels for 5.1 are lit however there is no sound at all. AAC shows no signs of decoding (no speakers lit).
2.0	All settings switched on EXCEPT transcoding resulted in audio for 5.1 streams but AAC still not playing and no sign of decoding.	Obviously no sound at all and no suggestion of it being decoded; this includes both AAC stereo and 5.1.

Any clues on other things to try? Seems AAC is basically impossible.   

I see you are running LibreElec. What audio device have you chosen in Kodi as your main (and in the case of bitstreaming Passthrough) device?

AAC won't be passed-through as AAC - so you have a choice of PCM 2.0/5.1/7.1 (i.e. no Dolby Digital Transcode enabled and 5.1/7.1 configured in Kodi) or PCM2.0/DD5.1 transcode (i.e. Dolby Transcode enabled and 2.0 configured in Kodi)

It sounds as if there is an issue with your Kodi+OS+AVR in outputting 5.1/7.1 PCM multichannel ?

It may be there is a 5.1/7.1 PCM output issue with Linux (i.e. LibreElec) with very new Intel devices - might be worth asking at the LibreElec forum?  This is unlikely to be an AAC issue - it's more likely to be a PCM output issue.  (AAC decoding to PCM is pretty straightforward and has been supported for ages)

[jjd-uk]

What is the device? as many ARM devices do not handle Multichannel PCM correctly which is required here. Could you try with the 5.1/7.1 FLAC test files from https://github.com/sfiera/flac-test-files to see if you get the same.

If you have a device which has issues with Multichannel PCM then the only solution is transcode to AC3.

[noggin]

What is the device? as many ARM devices do not handle Multichannel PCM correctly which is required here. Could you try with the 5.1/7.1 FLAC test files from https://github.com/sfiera/flac-test-files to see if you get the same.

If you have a device which has issues with Multichannel PCM then the only solution is transcode to AC3.

Original Post says it's an Intel NUC - and subsequent posts mention LibreElec.

[auldthief]

Irrespective of how many you actually have, set number of speakers to 2. Enable all pass through options. Worked for me for 2 aac files.

[noggin]

Irrespective of how many you actually have, set number of speakers to 2. Enable all pass through options. Worked for me for 2 aac files.

If you do that then all 5.1/7.1 content that is in AAC, FLAC, PCM multichannel etc. will be decoded and re-encoded (i.e. transcoded) to Dolby Digital 5.1 lossy.  This means a quality loss.  If your Kodi platform and AVR support HDMI 5.1/7.1 PCM you are far better to let Kodi decode and output these formats to PCM 5.1/7.1 (which requires you to set the speaker number to 5.1 or 7.1 etc.).

If you keep the speaker number to 2 when you have a 5.1/7.1 PCM-compatible system you won't get 5.1/7.1 PCM output and instead will get the option to transcode to the poorer quality, lossy, Dolby Digital format and output this transcode as a bitstream, but this will have a quality impact.

(5.1/7.1 PCM is the same audio quality as Dolby True HD or DTS HD Master Audio - all three are lossless ways of carrying audio.  The only real difference is that True HD and DTS HD MA have metadata to allow AVRs to do some additional processing in some circumstances.  All are better quality than a lossy Dolby Digital output)

The main reason to run with speakers as 2 and Dolby Digital Transcode enabled is if your system can't cope with 5.1/7.1 PCM output over HDMI and you have to use a legacy 2.0/AC3/DTS connection using SPDIF/TOSLINK or the equivalently limited ARC or have a platform that can't output 5.1/7.1 PCM (some Android players for instance)