Postby GWBasic » 08 Oct 2009 21:36
I have this same problem... It's VERY annoying. This happens on both my Mac Pro and Mac Mini when I use SPDIF. When I use the analog out, the volume issue goes away.
What I see is that the volume jumps to 400% whenever AC3 or DTS is used. (Specifically, this is when VLC sends AC3 or DTS to my reciever.)
For example, I just played a DVD that uses PCM in the menu. When the DVD started, the music was loud and distorted, so I turned the volume down to 100%. As soon as I started playing, the soundtrack was AC3, so VLC's volume jumped to 400%. My receiver indicates that it's getting AC3 and there is no distortion.
VLC's default volume changes whenever I do AC3 or DTS over SPDIF, so if I set the default volume in Preferences, it changes back.
(For those not familiar with how AC3 and DTS work, they send encoded audio through the SPDIF to the receiver. Both AC3 and DTS rely on the stream being bit-for-bit exact, so if VLC tries to do any form of processing on the stream it will result in static. Therefore, VLC can not alter the volume when sending AC3 or DTS over the SPDIF.)
Again, this is very annoying.