On Mon, Oct 08, 2001 at 08:15:15PM -0400, David I. Lehn wrote:
> When using the downmix code in liba52/libao there is a low-volume issue.
> For instance on a DVD player when downmixing to stereo the menu's may be
> in stereo but the movie will be 5.1. So when you switch between them
> you have a very loud menu and very quiet movie. I assume this is just
> due to whatever averaging the code is doing to avoid clipping in the 5.1
Yes, this is the A52_ADJUST_LEVEL thing - it adjusts the level
according to the downmix mode, to avoid overflows in the output.
One solution is to not use the A52_ADJUST_LEVEL flag and use a
constant level - probably you want to calculate it for the worst case
downmix. That way all downmix modes will use an equally low level.
> Has anyone found a solution for this problem? Anyone know how hardware
> and/or commercial players handle this? I've not noticed it in any
> commercial product.
I'm not sure how commercial players work. I've been told they sound
louder than a52dec - so I suppose they just use a constant level,
higher than what a52dec uses. That would mean they can saturate their
output at times - something a52dec carefully avoids. However a lot of
people think that louder is better... I'm not sure how to handle this.
Michel "Walken" LESPINASSE
Of course I think I'm right. If I thought I was wrong, I'd change my mind.