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Full Version: Is there a way to configure audio downmix settings?
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Although my HTPC has an SPDIF output, my ancient Sony DAV-S300 receiver only has a stereo analogue input with Dolby Surround (Prologic) support.

I recently started using Vidcoder and noticed that it removes the sub channel when doing a Dolby Surround or Dolby Prologic II downmix from an AC3 source. However if I keep the original AC3 soundtrack, when the resulting file is played back in XBMC the sub channel is preserved, which sometimes causes distortion. I have the "boost on downmix" audio setting checked because otherwise the output from the HTPC is pretty quiet compared to my other sources.

What I would like to do is keep the original AC3 soundtracks in as many of my DVDs as I can when I rip them, because no doubt I'll move to a better receiver in the future. It'd be nice therefore if I could control XBMC's automatic downmixing a bit better to reduce the sub channel a bit and maybe boost up the centre channel too. I used to use AC3 Filter with Windows Media Center before switching to XBMC and it gave me a lot of settings to fiddle with in that respect and I find myself missing them.

Is there a way to do something similar in XBMC?
I had a little more time to play with this today and it seems to me that Handbrake (the engine used by Vidcoder) does a really nice Prologic II downmix that my receiver is able to play very well.

I grabbed a simple AC3 5.1 test file and downmixed it in Vidcoder,The resulting MP4 sounded really good coming through my receiver, with a nice sense of direction from the rear surrounds. However, the original video with AC3 sound does not sound nearly as nice coming straight from XBMC - there was virtually no rear separation at all.

If anyone would like to try and compare for themselves I've uploaded the files (only about 2mb worth) to my Skydrive here:


When you play them make sure you are playing via a simple stereo analogue output to a Dolby Prologic or Prologic II compatible receiver. Despite the missing sub channel, I reckon the handbrake downmix sounds much more directional than XBMC's realtime downmix of the original AC3 file.

I would dearly love to get at some settings to let me tweak this.
No way to configure this. Which version of XBMC are you using ? There is a largely reworked audio engine in version 13 alphas
Thanks for that.

I'm still on Frodo (12.2). I'm almost certainly going to move to Gotham as soon as the first stable release comes out and my favourite skin is updated (Aeon Nox). Looking forward to seeing if any more audio configuration parameters are exposed to the GUI when the time comes.
There are a few more, but not directly related to this.
The new AudioEngine does, however, handle a lot of situation better - it was redesigned from the ground up.