Let me understand audio passthrough please
#1
Hello,
I have been using Kodi for many years, always using audio passthrough to my AVR. If I understand it properly, in this mode Kodi just send data 1:1 to AVR for decoding. What if I disable passthrough - is Kodi decoding audio instead of AVR ? I will not get "DTS:X" or "Dolby Atmos" message on AVR anymore, but something like "Multi channel". I don't really care about AVR display message as long as I get proper sound from speakers. But do I get it ? Is it exactly the same regarding sound quality and proper surround positioning ? Are built-in Kodi decoders same as those in AVR ? What about HD audio (TrueHD/HD Master), can Kodi decode those as well ?
Thanx a lot :-)
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#2
If your AVR says Multichannel then Kodi is decoding it and sending it to the AVR. This is a discussion that has been had many times on this forum, it might help to do a quick search.

As to whether you are getting the same sound out of your AVR if the decoding is done in Kodi or the AVR is a bit of a religious argument which I won't get into. However, if you want The AVR to do the decoding, the key settings are:

Settings>System>Audio
Audio output device - HDMI (capable receiver, cable etc)
Number of Channels - 7.1 (or whatever setup you have)
....
Allow Passthrough - Enabled
 ...other settings probably should all be enabled since a receiver capable of HD audio usually can do everything else.
TrueHD capable receiver - Enabled
DTS-HD capable receiver - Enabled

Settings>Player>Videos
Sync playback to display - Disabled (This is the setting that is usually missed)

Hope that helps,
Cheers,
LongMan
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#3
Thanx for reply, that's exactly what I use with my 7.1.2 setup and it works nicely. What I meant to ask was if I really need Nvidia Shield for HD audio or not. I understand it's only Android TV device with HD audio passthrough, but if I let Kodi decode it, it could work for any other ATV boxes out there (Chromecast Google TV, Mi Box...) ? So I should be able to ked proper HD audio ("uncompressed bluray" Dolby Atmos/DTS:X) from any ATV box if I let Kodi decode it.
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#4
When Kodi decodes it, kodi send PCM, so it should work. I can't speak for the devices that you mentioned but LibreELEC 10 Generic on a NUC and Raspberry Pi 4, it works.

Cheers,
LongMan
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#5
I think you'll only get up to 7.1 using PCM and not 7.1.2.
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#6
It seems you are right. The only standards for PCM are 2.0, 5.1, or 7.1 channels. So no HD Dolby Atmos / DTS:X over PCM.
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#7
Correct me if I'm wrong here, but I've always been under the impression that the 'number of channels' option has no effect on the passthrough portion of how Kodi handles audio, since the audio is being passed through unmodified in any way shape or form (including channel count).

Also, setting 5.1/7.1 sound on non - digital sources (DTS, Dolby Digital, etc, etc.) will force Kodi to process / upmix to the set channel count specified, thus probably preventing the AVR from itself upmixing stereo content via standards like Dolby ProLogic and DTS: Neo, etc.

It's always been the case in my setup, to run the top section of the settings menu (i.e the part that refers to anything not being passed-through) at 2.0 Stereo, disable Stereo Upmix, and let the AVR invoke Dolby ProLogic for stereo content. This might not work so well for multi-channel 'AAC' audio in a video file though. This section of the kodi settings is somewhat confusing, admittedly.

EDIT: I think I'm right in saying (again, correct me if I'm wrong) that you also ought to avoid any sound enhancement settings as provided by Windows sound properties / device settings, and/or software enhancements like 'Dolby Atmos for Headphones' as provided by Windows, if using a dedicated amplifier as it modifies the sound stream prior to the AVR receiving it, hence you no longer have bit-perfect audio streams. Your amp either has the required support, or it doesn't. Trying to force it via software isn't the correct way to get it working AFAIK.

Dan / Gib.
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#8
(2021-12-04, 20:53)gibxxi Wrote: It's always been the case in my setup, to run the top section of the settings menu (i.e the part that refers to anything not being passed-through) at 2.0 Stereo, disable Stereo Upmix, and let the AVR invoke Dolby ProLogic for stereo content. This might not work so well for multi-channel 'AAC' audio in a video file though. This section of the kodi settings is somewhat confusing, admittedly.

Thanks for the pointer, I didn't consider that. Are you seeing a difference here in what the AVR does? Have you actually tested it?
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#9
(2021-12-04, 21:59)LongMan Wrote:
(2021-12-04, 20:53)gibxxi Wrote: It's always been the case in my setup, to run the top section of the settings menu (i.e the part that refers to anything not being passed-through) at 2.0 Stereo, disable Stereo Upmix, and let the AVR invoke Dolby ProLogic for stereo content. This might not work so well for multi-channel 'AAC' audio in a video file though. This section of the kodi settings is somewhat confusing, admittedly.

Thanks for the pointer, I didn't consider that. Are you seeing a difference here in what the AVR does? Have you actually tested it?

It outputs Dolby Digital and DTS just fine with it set to Stereo 2.0, if that's what your asking. And yes, all speakers are utilized. My setup is a bit quirky, as I have a 5.0 system. I have no need of a dedicated subwoofer, but my Onkyo TX-NR515 does handle passthrough as I expect it to, even with the 'number of channels' setting set to 2.0. Never specifically tried with AAC multi-channel. But the AVR does (correctly) upscale stereo audio to Dolby ProLogic / DTS: Neo if I have those modes selected on the AVR. The confusing thing on my Onkyo being that it displays the 'PCM' icon regardless of what is being received. But at the same time it will also display the correct 'DD' or 'DTS' logo when applicable.

Dan / Gib.
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#10
I was thinking more of what happens with the stereo tracks. Does kodi actually upscale even if Stereo upmix is disabled when Number of channels is set to 7.1
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#11
My AVR also has a setting for how to handle 'other multi-channel sources' (aside from Dolby / DTS supported formats) but I've never really played with that in fear of breaking something elsewhere. It may be the case that setting your number of 'audio channels' to the number of installed speakers on your system may yeild better results for lossy multi-channel audio like AAC Multi-channel audio, but if your AVR does support Dolby ProLogic / DTS: Neo, leave the "Stereo Upmix' setting off, and let your AVR handle that, otherwise Kodi will likely be the one doing the grunt-work, and not your AVR (unnecessarily) and thus putting extra load on Kodi where it's not needed.

For true digital multi-channel audio (DTS. Dolby Digital, Atmos, etc.) The passthrough settings ought to take care of that. But you have to be mindful to only select the formats that your AVR supports. Kodi doesn't always get it's determination of your AVR's feature set correct (It doesn't with my AVR), which means I have to turn some format options on manually. But then again, I also have a Pulse Eight CEC Adapter in the mix that I find the configuration of equally as confusing (read: hit & miss), and their documentation is practically non-existent, so that might be skewing things with regards my setup.

Like I said above. This is how I understand it to work - I'm no audiophile/audio hardware expert. So YMMV.

Smile

Dan / Gib.
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#12
(2021-12-04, 23:26)LongMan Wrote: I was thinking more of what happens with the stereo tracks. Does kodi actually upscale even if Stereo upmix is disabled when Number of channels is set to 7.1

No. And that's the point. Your AVR does. That's what Dolby ProLogic and DTS: Neo are for. To upscale Stereo Audio to output the optimum parts of the Stereo spectrum to the speakers that would most be suited to it. At least, that's the way I understand / interpret it.

Dan / Gib.
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#13
The *only* use for the stereo upmix setting (in my way of thinking) is if you are in a scenario whereby you have multi-channel speakers connected directly to your HTPC/device that do not support Dolby ProLogic / DTS: Neo onboard natively. In such a scenario you would have to get Kodi to do that for you prior to outputting that audio (hence stereo upmix) otherwise only the front speakers would be utilized. Since every AVR worth it's salt, should contain those features on-board, you shouldn't need to 'force-it' via Kodi.

Dan /Gib.
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#14
I have Denon X4700H receiver, which can handle/decode anything. That's not the issue. Problem is, there is no Android TV device capable of playing HD audio except Shield. Nothing against Shield, I actually have two Shields 2019 :-) I am just trying to find another option with Android TV... but it doesn't exists. It's a pity :-(
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#15
Probably because of the same reasons most graphics card manufacturers don't support HDMI-CEC. Licensing (money). I do know that most Intel CPU graphics cores don't support HDCP, so reliance on discreet graphics is required. They're happy to include HDMI-CEC on NUC devices as these are generally too weak (CPU) to be used for video transcoding, as a pose to full, desktop-sized boards which don't (generally). Supposition on my part and way off-topic, so i'll leave it there.

Wink

Dan / Gib.
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