[MPlayer-users] SBLive! + AC3 SP/DIF Output (ALSA/OSS)

[Norman Kohler]

On Sun, 12 May 2002 20:05:25 +0200
Stefan <stefan.mau at web.de> wrote:

> I use ALSA 0.9.0beta12 and the Digital Output works fine in other Audio
> Apps, except mplayer. There comes the same crappy noise as with the OSS
> driver. The strangest thing about this is that with videolan I can get
> perfect SP/DIF Output with the OSS kernel SBLive driver! (in contrast to
> that some said the dev list that the OSS kernel SBlive driver is buggy).

As far as I understand, mplayer is based on a different synchronisation
method and the OSS driver has a bug with it...

> And when that isn´t possible somebody who explains me to get ALSA
> working! The ALSA documentation is crap and doesn´t help in any
> situation. Do I have to load a DSP emu10k1 patch or something, I don´t
> know what I should do more to get things work!
 
Here is how I got it working, but note that I'm using the Hoontech
extention hooked up to my sblive, so I can use a cinch or optical
socket... Okay, this is my modules.conf section - the last line of is most
significant:

alias char-major-116 snd
options snd snd_major=116 snd_cards_limit=1
alias snd-card-0 snd-emu10k1
options snd-emu10k1 snd_index=0 snd_id="Emu10k1" snd_extout=0x1f0f
alias char-major-14 soundcore
alias sound-slot-0 snd-card-0
alias sound-service-0-0 snd-mixer-oss
alias sound-service-0-1 snd-seq-oss
alias sound-service-0-3 snd-pcm-oss
alias sound-service-0-8 snd-seq-oss
alias sound-service-0-12 snd-pcm-oss
options snd-pcm-oss snd_dsp_map=0 snd_adsp_map=3

To get AC3 passthrough with mplayer, at least the alsamixer switch called
IEC 958 Optical Raw has to be set to on. BTW, you can do this with any
alsa capable mixer (like muting/unmuting) or quasi as a shorthand with the
following command:

amixer sset "IEC958 Optical Raw" on

Now mplayer has to be invoked like:

mplayer -ao oss:/dev/adsp -ac hwac3 -dvd 1

Don't forget to check /dev/adsp0 permissions and note that you have to
turn off the mixer switch mentioned above to get normal wave output again!
(Wave playback and AC3 passthrough don't work synchronously as far as I
can see...)

Norman

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