[mythtv-users] "Woodchuck" sound on TV playback

[Michael T. Dean]

On 08/15/2008 09:47 PM, John Welch wrote:
> One thing I'm curious about is step 6, where you say "turn on iec958
> in alsamixer".  In my alsamixer settings I've got a regular volume bar
> for IEC958.

Are you sure it's a "regular volume bar" (as there's no such thing as 
volume when it comes to IEC958--the receiver, not the computer, controls 
the volume).  I'd bet it's a 4-state switch (i.e. has 4 "volume" 
settings: 0, 33, 67, and 100).  Each setting does something different.

>   I've un-muted it and pushed it all the way up to 100.
> I've also got another "IEC958 Playback Source" setting, which I can
> toggle through four settings: PCM, ADC1, ADC2, and ADC3.  So far in my
> testing, if I set it to PCM I get the "static chatter";

That's saying that the IEC958 audio will be read from the PCM input on 
your sound card (here I'm talking inputs between chips on the sound 
card--not things you plug in).  On most all sound cards, that's the only 
input that's connected, so it's probably what you want.

>  if I set it to
> any of the other settings I get nothing.

If the switch I mentioned above is, "IEC958 Playback AC97-SPSA," or 
similar, try setting it to 0.  On this particular switch, the 4 
positions are:

0 (=0)  : PCM1
1 (=33) : PCM2,PCM1(rear)
2 (=67) : Center and LFE
3 (=100): PCM3,Modem,Dedicated S/PDIF

Sure, now you're thinking, "Well, wouldn't I want 3 for Dedicated 
S/PDIF," but you're not realizing that most all sound card (and mobo) 
manufacturers are too cheap to hook up the Dedicated S/PDIF.  Just trust 
me, if the switch is labeled, "IEC958 Playback AC97-SPSA," you want 0 
(unless you have a /very/ rare sound card with the S/PDIF connected (but 
then you want the "IEC958 Playback Source" set to something other than PCM).

If the switch is labeled something different and it's a switch (i.e. it 
has a /very/ low resolution for a volume slider), you may need some 
other setting, but you'll have to play around or research it yourself to 
figure out which one.

Note, also, if you get everything set up properly and it still doesn't 
work, it may just be your receiver doesn't properly detect AC-3/DTS.  
You can figure out if this is the case by doing an "iecset rate 48000 
audio 0" while playing the "static" sound from Myth.  If it switches to 
real audio...

Mike "I hate it when people call switches volume sliders" Dean
or
Mike "When will we all be able to use OSS4 so people don't have to learn 
all the idiosyncrasies (or idiocy?) of ALSA" Dean