Nobody has mentioned the “Volume amplification” setting. Make sure “Volume amplification” is set to 0dB, which should be the default. It’s in the audio settings dialogue when playing video, next to Volume and Downmix: Center mix level. After setting it to 0dB (if it is not already) choose to save this as default for all videos otherwise you are only changing it for one specific video.
If you increase Volume Amplification above 0dB it provides additional gain however any peaks that would otherwise clip with the extra gain go through a limiter / soft clipper and that would definitely chop all the dynamic range out of the peaks.
Optimal settings are “Volume 0dB” (this is the normal “volume” setting in Kodi and 0dB is the same as 100% elsewhere in the GUI) and Volume Amplification 0dB, which is the minimum setting for this slider.
With these two settings any two channel audio file should be rendered to a 2 channel output without any dynamic range compression and non lossy formats like wav should be bit perfect.
If you are playing back any multi channel (more than 2 channels) material with the output configured to 2.0 channels the down mixer will be active and this WILL apply dynamic range compression depending on how you configure the audio settings.
Check Settings->System->Audio “Maintain original volume on downmix”, I don’t recall which way around it is as the wording of the setting is a bit misleading, however one setting will apply dynamic range compression while downmixing and one will not.
Try playing something with AC3 audio and try both settings - whichever setting is quieter (and it should be pretty obvious which one it is) is the correct one to eliminate dynamic range compression.
In the original post it was stated:
But later it was stated:
I feel compelled to point out that there is nothing that Kodi or the Vero4k can do to selectively reduce the reduce the vocals by 7-8dB (that is a lot) in relation to the music - this simply isn’t physically possible if the original recording is 2 channel with music and vocals both mixed into the same two channels, unless the real problem is a change in frequency response that is suppressing midrange, but I can’t see why that would happen as there is no equaliser built into Kodi.
Are you certain that the files where you say the vocals are suppressed relative to the music are 2 channels and not multi-channel ? You talk about AAC at one point - AAC comes in both stereo and multichannel flavours… press ‘O’ during playback to bring up the codec info pane, this will tell you what type of audio it is decoding and how many channels the source file has.
If they are multi-channel including a centre channel then there is a known issue (IMHO) with the default downmix matrix when downmixing multi-channel audio to 2.0 stereo (no centre channel) where the centre channel from the multi-channel source is somewhat suppressed in level.
This can be compensated for by increasing “Downmix: Center mix level” in the Audio settings dialogue during playback by around 3-6dB, however take care to reduce the master volume (“Volume”) on the same page by the same amount otherwise you will introduce soft clipping and limiting on peaks which is exactly what you are trying to avoid…