Kodi 17.6 Not playing AC3, instead playing stereo
#1
OK, I have Kodi 17.6 on my Sony Android Smart TV. My Audio Receiver can only decode DD 5.1 and of course stereo.  The MKV I'm trying to play has both DTS 5.1 and DD 5.1 only, (no stereo sources whatsoever). When I play back the video I can only get Stereo. DTS is the first audio listed in the Matroska container and it was set to default, but I also set neither audio type to default and I got the same result, only stereo, no 5.1. If the MKV has both Stereo and DD 5.1, I only get Stereo.  If the MKV has DD 5.1 only, I only get stereo. The Smart TV is connected to the audio receiver via optical TOSlink cable, (it has no HDMI inputs).  Below are some of my settings:

Settings/Player:
=========
Adjust display refresh rate: Always
Sync playback to display: On

Settings/System:
==========
Number of Channels: 2.0
Output configuration: Optimized
Allow Passthrough: On
Dolby Digital capable Receiver: On
- Enable Dolby Digital (AC3) transcoding: Off
Dolby Digital Plus (E-AC3) capable receiver: Off

If I turn transcoding on I get DD 5.1 but the Audio and video are not synced.
If I turn transcoding on then off I get no sound whatsoever. I have to start the video over again.

All my media is on my NAS.
If I use the built in video player that came preinstalled on the TV, I get DD 5.1 no matter what format audio the MKV contains, except for stereo only that is, then of course I get stereo, which says to me that the problem is with Kodi; Yes/No?

I got Kodi 17.6 from the Google Play store.

Any help would be greatly appreciated!

Happy New Year!
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#2
From my own personal notes (but they should fix your issues)...

If the below is TLDR, then here are the important bits...

=12ptVideosàPlaybackàSync playback to display should always be set to OFF when using pass-through audio.
Output configuration: Best Match
Enable Dolby Digital (AC3) transcoding: On
Dolby Digital Plus (E-AC3) capable receiver: Off (Test the above to On first, make sure it works, then turn this On and test again to make sure audio still works). No all receivers support Dolby Digital Plus.

 
  1. =12pt- Change Audio output device to Android, RAW Passthrough (should be default).
    - The number of channels can be left to 2 (which is Stereo, but read below the Enable pass-through part).
    - Output configuration change to Best Match (If you notice sound issues, change to Optimized).

    =10.0ptBest Match

    =10.0ptThis looks at the audio properties of the file and picks the output format that most closely fits those properties out of the supported formats your device reports to Kodi.

    Benefits - If your device supports all the audio for formats contain in your files then it's to get works called "bit perfect" through, in laymans terms what we send exactly matches what we receive from the files, so 5.1 in for example will always result in 5.1 out.

    Downside - each time the properties received from the file changes then the audio system needs to be reinitialised with those new properties and some hardware does like this, so may result in very small audio drop outs as the hardware such as AVR copes with the change in what Kodi sends.

    Optimised

    This minimises changes in the audio properties of what Kodi sends, so it won't always exactly match the properties of the file, so in a playlist of files we take the properties of the 1st file and that is used for all subsequent files in the playlist even if they have different audio properties.

    Benefits - for hardware sensitive to audio property changes this minimises the chance of things like audio drop outs.

    Downside - If watch a live stream, if when you start watching it's send 5.1 then that is how audio is set up, if during a commercial break audio changes to 2.0 then we still send 5.1 , alternatively if you start watching during a commercial break with 2.0 audio then the TV show starts it's 5.1 then we still send audio as 2.0

    Fixed

    This is only available for audio we decode for sending as PCM as we must always have the ability to resample the audio. This is used where where hardware is sensitive to any change in audio properties, or the hardware does not perform well with certain sample rates.

    Benefits - audio should always be playable without any audible issues.

    Downside - not possible with passthrough audio, and depending on the audio properties of your files could result in audio being resampled a lot of the time.



    - Stereo upmix should be OFF
    -           However, you can enable Stereo upmix, it just outputs stereo sound to all speakers instead of the front. May be useful if you have to crank the volume to hear people talking. However, if you have a Receiver, don’t enable this feature.
    - Maintain original volume on downmix should be ON
    - Keep audio device alive can be set to 10.

    =10.0ptThe 'Keep audio device alive' setting keeps the audio device alive at the Kodi end, so where we need exclusive access to the audio device we maintain a lock on the audio device or other programs can't grab access from underneath Kodi. This is mainly an issue with Linux and Windows audio systems, I don't believe it's possible to get exclusive access on Android. 

    The 'Send low volume noise' setting ensures an active audio stream is sent to whatever external device you use for generating the sound (TV with speaker or AVR with speakers) as some hardware will drop the audio connection if it does see any incoming audio, this then prevents the possibility of the very start of a audio stream not being heard while the audio connection gets started backup. The 'Send low volume noise' setting is optional because although the noise pattern is done in such a way it should never be audible so all the human ear should hear is silence, however in practice some external hardware may alter what it received and end up producing some audible effect that the user can hear and may not be very pleasant.


    - Enable audio DSP processing should be OFF
    - Enable pass-through should be ON if you have a Receiver.
    - If you are connected to a Receiver? Then change the settings to use Pass-through. Also, the recommended “number of channels” settings is 2.0, even if you have 5.1 or a 7.1 surround sound setup. Because not all Receivers will accept pass-through if it’s set to 5. Even then, because Kodi is using a “hacked” method for passing audio over HDMI, pass-through doesn’t always work or work correctly with certain Receivers. The only reason to set it to 5.1 is if Kodi is doing the decoding and you are sending LPCM to your Receiver (this means that Kodi is doing the decoding and sending the decoded audio to your Receiver).

  2. =12ptIf you notice that Music (or really any video playing) is quiet, you can amplify the output by doing the following…
    - Start a Video, and bring up the OSD screen, go to Settings – Audio and Subtitle Settings
    - Go to Volume Amplification and turn it up.
    - This is a Global Setting and will work for everything.
    - If you are using Pass-Through (to a Receiver) then this solution will NOT work.

  3. =12ptFor Video settings…
    - basically the defaults are the best
    - Deinterlace AUTO
    - method Bob-Inverted
    - Bilinear
    - Post Processing ON
    - Both methods of hardware acceleration ON
    - High quality scalers 0%

  4. =12ptVideosàPlaybackàSync playback to display should always be set to OFF when using pass-through audio.
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Kodi 17.6 Not playing AC3, instead playing stereo00