At Wed, 23 Jan 2002 01:10:59 -0800,
Dean Townsley wrote:
> 
> > >Also, is there documentation of the registers beyond the #defines in the code?
> > 
> > Hurry up before it is gone:
> > 
> > http://members.home.net/puresoft/cmedia.html
> > 
> > The 5.64 version here is at least a bit longer than what is in the 
> > kernel currently. And it works.
> > 
> > Pity that the author gave no reply about where his files would move 
> > after @Home US will close :(
> 
> Thanks I got 'em just in case.
> 
> And I actually got the alsa driver working, but it's a real hack at this 
> point.  I'm going to bed so I'll post the patch in case someone wants to 
> fiddle with it more.
> 
> Brief explanation:  The alsa driver attempted to do  channel-> dac ->spdif  by 
> turning on the "dac to spdif".  The kernel driver, on the other hand, just 
> turns on the channel -> spdif directly.  I've just hacked the code so that the 
> alsa driver (in the working special case) just does the latter also.  I also 
> had to eliminate a mysterious 2 that was put in an undocumented register on 
> initialization, because it was not there in Thomas' dumps of the oss driver.
> 
> It's a nasty hack and doesn't test for anything like it should, but I get 
> non-distorted sound out of my stereo!  And direct Dolby digital is going 
> through too!  No sound out of the analog, but that can probably be fixed.
 
Hmm, the SPDIF_0/1 must be set when pcm #2 is opened..

Did you use the device hw:0,2 instead of default pcm?
i.e. to play via spdif you'll need to do like this:

        % aplay -Dhw:0,2 foo.wav

The "IEC958 Output Switch" exists as an extra switch in order to allow
SPDIF looping.


BTW, there is a bug in the driver for the chip model 033 wrt AC3
transfer.  On this model, AC3 (non-audio) data is transferred with
software encoding (emulation).  And this seems not working.

Most of AC3 receivers can detect signals even as a normal spdif
packet, so maybe ac3dec can work like:

        % ac3dec -C -Dhw:0,2 foo.ac3

so that AC3 software encoding is avoided.


Takashi

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