Audio downmix issue with v17?

Settings / Player: Videos
Actions:
Play next: No
Skip steps (defaults)
Skip Delay: 750ms
Playback
Adjust display rate: Off ← Changing this to “On start/stop” or “Always” breaks the audio
Sync playback to display: no
Display 4:3 videos as: normal
Processing
Allow hardware acceleration - OMX player: on
Allow hardware acceleration - MMAL: on
Limit GUI updates during playback: 10fps
Stereoscopic 3D
Playback mode: Ask me
Disable 3D mode when playback ended: yes
Decode stereo stream from 3D file: yes
Teletext
Activate teletext: yes

  • Scale teletext to 4:3: yes

Thanks,
Roger

Hi Roger,

Nothing looks out of place there. What if you try as actiona original suggested, set audio to 2.0 with passthough enabled?

Thanks Tom.

I’m having a similar issue with my OSMC on an RPi 3. I believe it first started with 2017.03-1. Today I upgraded to 2017.04-2 and the problem persists.

RPi 3 connects via HDMI to a Yamaha RX-V767 receiver. TV is a Sony with 24 Hz support.

Passthrough is off. Output is HDMI only. Channel setting is 5.1.

With setting “Player -> Videos -> Adjust display refresh rate” set to “on start/stop”, for a 24 fps video the refresh rate is updated and my TV shows “1080/24p”. (GUI refresh rate is ~60 Hz.) The audio source is 5.1 channels but with the resolution/refresh rate update, the receiver is only registering a 2-channel input (2.1). If I manually toggle “stereo downmix”, the audio output is updated to the proper 5.1 channels.

Changing the setting “Player -> Videos -> Adjust display refresh rate” to “off”, preventing refresh rate change, and Kodi properly sends the 5.1 channel audio to the receiver from the beginning.

Those are my two workarounds for now.

I can’t see anything in the logs which would indicate why this is happening. If this is not a know issue, are there verbose logging options for this refresh rate update or something else?

I would like to ask WHY you put pass-through to “off”. I have a similar setup but I would like my receiver to do the decode work (to reduce CPU load on PI/Vero), Therefore I run with passthrough “on”. I do have 7.1 speakers and let my receiver play with the signal… (which works on PI3, but not on Vero).

Thanks,
Oliver

OK, so in a way, I’m pleased it’s not just me… although I’m sorry to hear that you’re having problems too, @logan893.

Your problem sounds identical to mine.

If you have passthrough enabled then switching between audio streams isn’t that nice if you are switching between passthrough and non-passthrough modes (as I commented on earlier).

Unfortunately, the more recent high def audio streams won’t passthrough to my receiver so I have to use PI decoding for those, hence the issue. E.g. “Puss in Boots” has a “Dolby TrueHD 7.1” audio track…

Hi @Tom_Doyle, if I do that, it works as expected. Passthrough works… and non-passthrough gets correctly downmixed to 2.0 with no channels obviously missing. Of course, now I only have stereo sound, so it’s not a preferred option although it may be an important test result.

Hi,

Thanks for doing these tests, sorry it hasn’t really resolved the issue; but it should give the developers a better idea of whats going on.

There is an incoming update, so please keep a eye on the news section/blog. Please test again, then.

Thanks Tom.

Thanks @Tom_Doyle, I’ll keep a look out. It seems I’m not the only one reporting this problem so let’s hope it’s fixed soon. It used to work ~6 months ago so hopefully it’s not too difficult to spot where the problem was introduced.

1 Like

A bit of a stab in the dark, but if you have an audio issue that only occurs when “adjust display refresh” is enabled, can you try adding “hdmi_muting=0x03200192” to config.txt and see if it helps.

Hi @popcornmix, just tried that but unfortunately no luck, the issue remains. What did this change do?

I don’t know how Kodi is constructed, but would it be possible to change audio stream just after the video rate change then change the stream back again? If I do this manually from the UI, it seems to fix it…

I’m happy trying to patch it if it’s Python script or similar - but I’d need a bit of guidance. If it’s C / C++ then I’m a bit nervous about rebuilding the whole Kodi application… although I suppose it should work smoothly enough if I can get the build environment correct…

Some info here

Changing the audio after video is not really possible in kodi.
In theory refresh rate can change many times in a video and kodi will adjust display refresh when it detects this.
Sometimes the refresh rate reported in the file header is incorrect and kodi will change again after a few seconds when it has decoded enough frames to be more sure.

So there’s definitely a bug somewhere then.

If I have set the audio config as 7.1 and enable passthrough, then I select a movie with Dolby TrueHD 7.1 and DTS 5.1 streams, when the movie starts, I get 5.1 PCM on the HDMI and the audio stream selected is the TrueHD stream. If I switch this to the DTS stream, I correctly get DTS passed through. If I switch back to the TrueHD stream, I now get the correct 7.1 PCM on the HDMI.

Somehow, across the refresh, the audio configuration gets confused. I can’t see how it’s the amp causing the problem - it has to be something somewhere in the PI that’s misconfiguring the audio channel setup or misconfiguring the embedding into the HDMI stream.

Thanks for all the help so far on this…

Can you test powering the amp off and on again while the audio is playing incorrectly.
I’d be interested to know if that corrects it or not.

@popcornmix - Nope. Doesn’t fix it either.

If I put the amp in standby, the HDMI goes into what it calls “bypass” mode. The TV now plays the video and audio… but it is still missing some of the channels (I don’t know what the exact audio format is going to the TV).
When I bring the amp out of standby, the audio channels are still showing as 5.1 with missing audio (should be 7.1).

If I actually pull the mains plug on the amp then the TV loses its input completely. When I plug the mains back in again to the amp, the picture comes back… and the audio still is 5.1 with the missing channels.

You are using omxplayer which is neither the default nor recommended on PI2/Pi3.
Can you try disabling that (but leaving MMAL enabled).

Wahey! Thanks, @popcornmix, that’s sorted it!

Thank you very much for your help.