[mythtv-users] One HDMI question from (Hijacked): HDMI sound issues

[Raymond Wagner]

On Aug 28, 2013, at 4:37, Stephen Worthington <stephen_agent at jsw.gen.nz> wrote:

> On Wed, 28 Aug 2013 18:04:54 +1000, you wrote:
> 
>> On 28 August 2013 17:57, Stephen Worthington <stephen_agent at jsw.gen.nz> wrote:
>>> A digital signal is a digital signal.  It is either correct data, or
>>> it does not work.  So the digital output from an SPDIF port will be
>>> identical to the output from a TOSLINK port, as far as the
>>> specifications for the digital data are concerned.  If you are really
>> 
>> it's a very simplistic view of things...
>> 
>> It's definitely possible to get corruption one long cable; same as you
>> can get digital interferences if you use a very long, not great
>> quality hdmi cable
> 
> In which case the cable is faulty.  By definition, an HDMI cable must
> put out a signal that meets the HDMI specification.  If it puts out a
> corrupt signal, it is not an HDMI cable.  That is the fundamental
> difference between an analogue signal and a digital one.  There is no
> such thing as a degraded or corrupt digital signal - that is a faulty
> digital signal.

Sure there is.  If you have no error recovery in your data stream and are sending raw audio/video, you can have a degraded signal on the other end just as you would for analog transmissions.  DVI behaves in this manner.  HDMI on the other hand does use error recovery, so you'll get perfect reproduction right up until the point you lose large chunks of signal.

> HDMI signals were never supposed to work over long distances - that
> was never part of their design.  If you want a really long HDMI cable,
> it will need one or more regenerators in the cable (and power for them
> to work from), or it will need to convert the HDMI signal to something
> else (eg ethernet) that will travel over a longer distance, and then
> be reconverted to HDMI at the other end.

That's not Ethernet, it's still HDMI. All they're doing is discarding the grounds, and retransmitting the remaining lines at much higher power levels over the 16 (much thicker) conductors of two CAT6 cables.