[mythtv-users] HDMI_SPDIF directly to reciever

[Johan]

On Fri, 2008-07-04 at 22:16 -0700, Alen Edwards wrote:
> 
> 
> James wrote: 
> > Roo wrote:
> >   
> > > 2008/7/5 James Lockie <bjlockie at lockie.ca>:
> > > 
> > >   
> > >     
> > > > There is 0 volts on the RCA.
> > > > 
> > > > Why do I get sound if there is a zero volt signal?
> > > > I tested my voltmeter on a battery to verify it works.
> > > >     
> > > >       
> > > James,
> > > 
> > > If your voltmeter is on a DC range and the output is bipolar, +0.5V
> > > and -0.5V then that will "average" out to 0V. This is irrespective of
> > > the data travelling over the spdif as it is Manchester Coded.
> > > 
> > > Try an AC range on the voltmeter if you have one.
> > >   
> > >     
> > AC is 3 something.
> > So if my receiver expects 5V and it is getting less, am I hurting it?
> > 
> >   
> > > HTH,
> > > 
> > > Roo.
> > > ___________________
> > 
> If you are getting 0 DC and 3AC, I am surprised.  I would expect it to
> be the other way around (0AC and 2-3DC).  No matter, less it good and
> your receiver is probably saying it can take anything up to 5 volts
> and it can probably take much less, like maybe .1 volts.  Some people
> on this list have said their equipment works all the way to .025
> volts.  I would double check your numbers and readings then try it.
> 
> 
> Allen
> 
> _
Summarizing:

the signal is digital manchester coded and probably bipolar, so will not
contain a DC component.
It's sampling rate is up to 96kHz, to high for most multimeters. 
Multimeters do not measure peak values, but only average (they are even
"calibrated" in RMS (root MEAN Square). So you will never know what peak
voltages are actually present. 
Only way to be sure is to use an oscilloscope.

know it does not help, but clarifies a shortfall in the measuring
technique..

Johan
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