[FFmpeg-devel] [PATCH] rematrix DPLII fix for channel downmixing. Surround now adds to front rather than taking away.

[Hendrik Leppkes]

On Sat, Mar 15, 2014 at 4:46 PM, Peter Robertson
<Peter at corrosivetruths.org> wrote:
> This fixes a problem where trying to convert gameplay sound to Dolby Pro
> Logic II would result in a left channel that would be missing the sounds
> that were in center and back left at the same time. I also applied it to
> Dolby Pro Logic as it should work the same way. Sorry if I've done
> anything wrong, first patch. Fixes #3455
>

The encoding matrix for DPL/DPLII is defined by Dolby, and only sounds
good if you use a DPL compatible decoder to reconstruct the original
signal.
Its not necessarily supposed to be played as stereo through stereo speakers.

All Information I could find about DPL encoding suggests that the
implementation is correct as it is today. Left channel subtracts both
surrounds, and right channel adds them.

- Hendrik