[DBMandrake]

"Maintain original volume on downmix" has no effect on 5.1 audio mixed down to 2.0 like it does on other platforms. (Mac/Windows) This problem was actually there in Gotham as well, but only for OMXPlayer - DVDPlayer did boost the volume when turning off "Maintain original volume on downmix". However now that DVDPlayer and OMXPlayer are somewhat merged, it seems to have followed the behaviour of OMXPlayer, eg the setting is not doing anything.

For dvdplayer this should behave the same as other xbmc platforms. If it's not that needs further investigation.

The new "Boost centre channel when downmixing" is not working for me, I can turn it up to 20dB on a 5.1 channel file and notice no difference. This is the case with either setting of "maintain original volume on downmix".

There have been a number of reports of this working successfully. Note: it only works when audio is downmixed to stereo. e.g. number of channels is 2 and passthrough is disabled.

Yes I'm testing with 5.1 ac3 audio tracks downmixed to stereo.

Found out what's happening - I didn't realise that none of these settings have any effect during playback with omxplayer - I guess it only reads the settings before playback starts. My fault for not testing thoroughly enough.

dvdplayer responds to the "maintain original volume on downmix" setting on the fly (but not "boost centre channel when downmixing" - that needs the video to be restarted) while omxplayer needs the video to be restarted for either setting to take effect.

Both settings seem to be working with both players - "maintain original volume on downmix" being turned on is boosting the overall volume by roughly 10dB on the clips I tried.

I did notice however that "boost centre channel when downmixing" only works when "maintain original volume on downmix" is turned on - is this by design ? That doesn't really make sense to me because (a) it means you can only boost the centre channel volume when you're already applying compression and boost and (b) when you're NOT applying compression there is more headroom available to take advantage of the centre channel boost, so it doesn't make sense to prevent it's use in this situation. (Especially when the GUI doesn't make clear that this will happen)

"Play GUI sounds: always" is not working for me either - as soon as I start playing a video GUI sounds go silent, however if I change one of the sound settings such as "maintain original volume on downmix" WHILE the video is still playing I get an extremely loud distorted GUI click sound then after that the GUI sounds start working again while the video still plays, until I stop and play the next video then GUI sounds stop working again.

dvdplayer or omxplayer? I'd expect this to work for dvdplayer (and paplayer), but probably not for omxplayer (which closes down audio engine when starting).
I guess adjusting audio settings when omxplayer is playing is re-enabling audio engine - would be better if that were disabled.

Yes it appears the "play GUI sounds" setting only works with dvdplayer and has no effect on omxplayer - regardless of setting there are never gui sounds during playback unless you change an audio setting on the fly during playback such as "maintain original volume on downmix" in which case the GUI sounds start working again regardless of what "play GUI sounds" is set to, although this only lasts until a seek at which point GUI sounds are disabled again.

Sound quality through the analogue output is particularly poor verging on unusable on some videos that have quieter scenes, at least without using volume amplification in the OSD, although this was also the case with Gotham so I think it's more of a limitation of the Pi hardware than an xbmc problem. A good example is the opening minutes of Gravity where the quiet comms speech to the astronauts is completely obscured by noise and distortion and unintelligible but audible and clear with HDMI output or played through analogue on another platform like my Mac. I'm doing further testing with the analogue output to try to get a better idea of what's going on, although I suspect not many people use the Pi's analogue output with xbmc/kodi so not many may notice or care.

Have you got kodi's volume set to full? Having a low software volume in kodi with a high volume on TV will produce bad audio, especially from the analogue audio with it's limited dynamic range.
BTW, a big improvement to analogue audio is coming soon....

Yes, I always leave the master volume in xbmc/kodi set to 100%.

I'm intrigued to see what will be done with the analogue audio - as I mentioned elsewhere dithering definitely doesn't seem to be working at the moment possibly due to the dither being too low in amplitude. Even with "maintain original volume on downmix" turned on and 3-6dB of centre channel boost quiet sections of many of my movies are still drowned in noise and distortion on the analogue output - the only thing that really gets the levels high enough to minimise this effect is the OSD "volume amplification" setting, which I don't like to use unless absolutely necessary as it effectively implements a hard limiter.