[MPlayer-users] 4-speaker support

[BlackRider]

On Sun, 18 Nov 2001 03:41:26 +0100
Felix Buenemann <atmosfear at users.sourceforge.net> wrote:

> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html &
>  http://gcc.gnu.org/gcc-2.96.html if you still have questions or problems]
> 
> On Saturday, 17. November 2001 19:48, you wrote:
> > > > is support for 4-speaker audio output planed?
> > > The prob is there is no real 4 speaker support on linux yet that I'd know
> > > of...
> >
> >  SB Live has 4 speaker support with the OSS driver (included in the
> > kernel). The front two speakers are in /dev/dsp and the back two speakers
> > are in /dev/dsp1. Maybe you could add a command line switch like that:
> > -fsd <front sound device> -bsd <back sound device>
> >  Does anybody know of another linux sound driver supporting 4 speaker
> > output and how it is supported?
> Ahh nice thing, last time I read up on this creatives docu just stated that 
> rear speakers are reversed l/r of front channels.

in SoundBlaster Live under Linux Frequently Asked Questions is:

Q.C1- What features are currently supported?
     Stereo wave audio input and output
     Rear speakers are stereo-mirrored
     ...
I don't know if it means that rear speakers are just mirror of front speakers or
that LR channel is played by RR speaker and RR channel is played by LR speaker.
     
but I have 4 dsp devices in my computer:
	internal SiS
	bt878 audio dma
	Live! front speakers
so 4th dsp is probably Live! rear speakers but I didn't test it yet

> Actually thing to do then would be:
> - someone with insight to libac3 should write a 5.1 to 4 downmixing method 
> (maybe there already is, but guess not)

5 to 2 downmixing is 10 lines of code... 5 to 4 should be even easier...

> - add support to mplayer core to handle two audiostreams or add a new pcm 
> format that multiplexes the four channels into a stream or already do this in 
> libac3, I suggest second way it's much cleaner
> - add support two ao_oss to handle AFMT_4CHANPCM or whatever it's named and 
> demux it two two several pcm streams that are then written two the different 
> dsp devices.
> 
> Btw. one also could enhance it to possible 3 dsp devices, so one could get 
> full 5.1 decoding without downmixing with for example sblive + onboard 
> soundcard.

sounds good but it will need some hardware hacking to speakers :) but my
computer is ready for this: internal SiS+Live! :)

> -- 
> Best Regards,
> 	Atmos
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