[surfparadise]

Downmixing reduces volume, so if the audio is multichannel, it will be quieter than stereo sources.
Use "boost volume level on downmix" to compensate for this (although with the possibility of clipping).

By default xbmc doesn't allow the volume to go above 100%. If the audio source didn't encode with full range audio (e.g. only 25% of range is used) there is no way to get that back to full range.
There is an advancedsetting.xml setting you can add to mitigate this.

Code:

<audio>
<!-- Amount of gain (dB) to be applied to audio. Default is 12.0. Valid values are: -96.0 to 96.0. -->
<ac3downmixgain>12.0</ac3downmixgain>
</audio>

Note: despite the name, on the Pi this is applied to all audio types. Try setting it to 24, or 48 and you should find you can effectively set the audio to > 100%.
If the audio was full range to begin with, this may clip and distort, although in that case, reduce the xbmc volume until the clipping stops and you should have the maximum volume possible.

I have "boost volume level on downmix" on and it doesn't make a difference. I also tried setting ac3downmixgain to 48, and that didn't change anything, either. My advancedsetting.xml looks like this:

Code:

<advancedsettings>
  <audio>
    <ac3downmixgain>48.0</ac3downmixgain>
  </audio>
</advancedsettings>

Any other suggestions?

Thanks.

I try me too this option... without any result...

...it will be really really nice if anyone could fix the problem relative to the analogic audio output and the movie with AC3 audio track. The voice is really really low... impossible to enjoy.... There was an option in XBMC to increase the gain on volume output, but in not present anymore......

Thank you in advance.