[mythtv-users] [OT]HDMI, SPDIF, DVI Nvidia, etc

Robert McNamara robert.mcnamara at gmail.com
Fri Feb 20 15:50:36 UTC 2009


On Fri, Feb 20, 2009 at 7:36 AM, Calvin Harrigan
<charriglists at bellsouth.net> wrote:
> Robert McNamara wrote:
>>
>> On Fri, Feb 20, 2009 at 7:09 AM, Calvin Harrigan
>> <charriglists at bellsouth.net> wrote:
>>>
>>> The audio is being sent over the dvi, contrary to popular belief the hdmi
>>> didn't introduce audio in addition to the dvi spec.  They are
>>> electrically
>>> the same.  The audio data is interleaved with the video on the tdms
>>> lines.
>>>  HDMI really introduced hdcp, yay...
>>
>> Still wrong.  DVI supports HDCP.  If you are passing audio via
>> DVI->HDMI, it's using a DVI *connector* at one end, but the electrical
>> modulation is HDMI format, *not* DVI.  They are *not* electrically the
>> same, they are two separate modulations that can use the same
>> connectors.  DVI->HDMI which uses audio is HDMI modulation.  HDCP was
>> *not* introduced with HDMI, it was already present (and still is
>> present) in DVI.
>>
>> Robert
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>>
>
> I'm not sure that is the case, my old video card,set top box, dvd player
> knew nothing of hdmi and I was still able to connect via the dvi->hdmi cable
> and get video.
> Wikipedia seems to suppport the idea that they are electrically
> similar/compatible.
> http://en.wikipedia.org/wiki/Hdmi
>
> ************************************************************************
> A DVI signal is electrically compatible with an HDMI video signal; no signal
> conversion needs to take place when an adapter is used, and consequently no
> loss in video quality occurs. As such HDMI is backward compatible with
> Digital Visual Interface digital video (DVI-D or DVI-I, but not DVI-A) as
> used on modern computer monitors and graphics cards. This means that a DVI-D
> source can drive an HDMI monitor, or vice versa, by means of a suitable
> adapter or cable.
> ************************************************************************
>
> Calvin
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> mythtv-users at mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
>

Right, HDMI has a DVI compatibility mode.  The electrical signaling
between early versions of HDMI and DVI are similar, but not identical
(they also become more divergent as new versions of the HDMI
specification were introduced).  Just wanted to make clear that if you
are getting audio, that the signalling used is from the HDMI spec, not
the DVI one, regardless of which connectors are at which end.  The DVI
specification covers both the connector types and the signalling and,
strictly speaking, the DVI specification does *not* allow for audio.
Both formats allow for HDCP and, in fact, HDCP 1.0 was implemented on
DVI only.

Robert


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