[MPlayer-dev-eng] Audio question: stereo sound to 6 channel sound plugin

[Stephen Davies]

On Thu, 14 Mar 2002, Kis Gergely wrote:

> Hello,
> I would like to ask, whether it would be possible to extend the surround
> plugin to generate 6 channel sound instead of 4 channel. I have an SBLive
> 5.1 with six speakers, and would like to use the center/subwoofer even if
> the audio stream is only stereo. I think it could be done this way:
> 
> -mix the stereo sound together to get mono sound.
> -use a lowpass filter on the mono sound, and send it to the subwoofer.
> -use a highpass filter on the mono sound, and send it to the center.
> -the other 4 speakers would get the original stereo (or surround) data, as
> it works now.
> 
> This is not an official feature request, I only would like to know if my
> idea is feasible.

Hi Kis,

Its surely feasible.

The references I read don't generally recommend to send a mono mix to the
centre speaker due to the fact that it narrows the sound stage.

Its quite CPU intensive to do a tight low-pass filter at subwoofer type
frequencies.  The surround decoder uses a C based filter which probably
isn't fast enough to run a lot of taps - but there is MMX code also in
mplayer that may allow it.

I'll have a look at it.

Steve