Kodi Audio Settings Help
#1
I'm a long time Kodi user and my most recent iteration is via LibreELEC on a Raspberry Pi 3.

It's been running fine for several weeks, but has recently started to have some strange audio related issues and I'm calling into question whether or not my audio settings are correct. I have the output device set to HDMI, number of channels = 5.1, stereo upmix = disabled, passthrough = enabled. Playing content which reports 5.1 sound, shows through my amp (a Sony soundbar) as 5.1, 2 channels show as 2.0, etc.

A couple of weeks ago, I disconnected the USB drive connected to the Pi which stores some of my content and as I did this, I dropped it about 3 inches. I mention this because the odd behaviour I'm about to explain, began immediately afterwards (and I also had to copy 1 file over after I reconnected it, because the original seemed to have become corrupt).

So, since the above, everything with more than 2 channel audio (not just content on the drive which I 'dropped' (which only stores files, as the Pi boots from an SD card)) reported 7.1 channels via my amp's info display, and voices were playing extremely muffled, as if they were playing on an audio channel which didn't exist. In order to get back to some level or normality (2 channel content showing as 2.0, 5.1 showing as 5.1, etc), I had to change the NUMBER OF CHANNELS in the audio settings to 4.1...anything above this resulted in the symptoms I've just described. Some content with 5.1 audio still shows on my amp's screen as being 7.1 but now sound 'normal' (i.e. without the muffled voices).

Does this correlate with anything that anybody's come across before? Should my NUMBER OF CHANNELS setting be the number of channels which the audio device can handle? I'm stumped as to how this could have happened without me actually changing any of the audio settings. Thanks in advance for your help/suggestions.
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#2
Soundbars don't usually support multichannel PCM. They probably support AC3 (Dolby Digital) passthrough and possibly DTS passthrough.

If that is the case you want number of channels to be 2.0.
You want passthrough enabled and AC3 passthrough enabled. Leave DTS disabled for now.
You can also enable AC3 transcoding.

That should allow you to get multichannel output on soundbar.

When everything is working try enabling DTS passthrough and check playing a file with DTS audio still works.
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#3
Thanks for that!

According to the spec. sheet, my sound base (Sony HT-XT3) supports LPCM-2ch, LPCM-5.1ch and LPCM-7.1ch (it also supports DTS, DTS-HD and Dolby TrueHD). Does this change any of your advice?

I have previously set the NUMBER OF CHANNELS to 2.0, which ended up with all content being shown on the sound bar's display as LPCM 2.0 (as opposed to LPCM 7.1, which it does at the moment)...I seem to recall content with DTS 5.1 also showing as LPCM 2.0 after I did this, but I'll have to revisit.. It's hard to tell if the actual sound is different. Although it can process multi-channel audio, it of course only physically has 2.1 speakers and as I'm not an audiophile, trying to discern any difference in the audio is tricky (apart from very obvious changes, which I initially described).

Anyway, I'll sit in front of KODI later today and triple check that everything is set as you describe, then see what happens (unless my first line of this post alters any of your previous advice). Thanks again!
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#4
Still try my suggested settings. The results may be informative and it may provide a solution you are happy with.
More tests can be done with multichannel PCM later.
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#5
Smile 
OK, I tried everything you suggested and after testing a selection of content, everything seemed to play how it should and the sound bar's display no longer showed 7.1.

I then turned DTS back on and tested the same 5 video files and they still all played as I'd expect them to. Then, I changed the NUMBER OF CHANNELS back to 7.1 and went back to the same files...they all seemed to play normally. I'm going to leave DTS on (unless you think there's a compelling reason to leave it disabled?) but put the NUMBER OF CHANNELS back to 2.0.

From a technical standpoint, I have no idea what this tells us but I would be interested to know, if you have the time to explain. Am I right in thinking that enabling passthrough puts the responsibility of decoding certain audio streams onto the amp, rather than the Kodi host?

Thanks again for your help with this...it's much appreciated.
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#6
(2017-05-26, 18:30)GeorgeStark Wrote: From a technical standpoint, I have no idea what this tells us but I would be interested to know, if you have the time to explain. Am I right in thinking that enabling passthrough puts the responsibility of decoding certain audio streams onto the amp, rather than the Kodi host?

Yes. For AC3 and DTS files.

With other formats (e.g. multichannel AAC) there is no passthrough, so the choices are outputting as multichannel PCM
or transcoding to AC3 and then outputting that through passthough.

You need to set number of channels to 2.0 to allow the transcoding option.
It is possible the multichannel PCM option may give you issues.

There are samples here: http://kodi.wiki/view/Samples
Try the AAC 5.1 before you decide if your current settings are fully working.
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#7
Thanks again for all your help. Wink
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