[mythtv-users] HDMI and audio

John Finlay finlay at moeraki.com
Thu Nov 19 03:15:48 UTC 2009

Jim Stichnoth wrote:
> On Wed, Nov 18, 2009 at 4:21 PM, Patrick Doyle <wpdster at gmail.com> wrote:
>> On Wed, Nov 18, 2009 at 6:48 PM, Jim Stichnoth <stichnot at gmail.com> wrote:
>>> On Wed, Nov 18, 2009 at 3:31 PM, Patrick Doyle <wpdster at gmail.com> wrote:
>>>> a few days ago (see
>>>> http://www.gossamer-threads.com/lists/mythtv/users/406672) in which a
>>>> user was having difficulties getting HDMI audio to work with his Vizio
>>>> TV.   (Gee, I've got a Vizio TV as well.)
>>> The poster in that thread was talking about a Vizio TV with a DFP
>>> interface, which is different from HDMI.
>> OK, now I'm really confused...
>> a) What is a DFP interface?
>> b) I read "I have a Vizio DFP TV that I conect to my mythtv system using HDMI
>> (adapter) from a Nvidia 8600GT using DVI".  So I thought that meant OP
>> was connecting via an HDMI connector on the TV.
> I don't really know anything about DFP, but Wikipedia indicates it's
> an interface along the lines of HDMI or DVI.  I assume the OP wanted
> to connect a DFP TV to an HDMI nVidia card.
Actually I have a Vizio TV that is connected to my MythFE/BE via a DVI 
cable thru a DVI-HDMI adapter; i.e on the Vizio side I use HDMI1 and on 
the PC side it's DVI. The DFP (Digital Flat Panel) just refers to the 
Nvidia designation used in the xorg.conf file.

I was trying to use the analog audio input in conjunction with the  HDMI 
video input and NOT digital audio over HDMI. The problem was that the 
EDID of the Vizio HDMI1 supports digital audio input and the Nvidia card 
was supplying a null HDMI digital audio. This caused the Vizio to ignore 
the analog audio input.
>>>  In the end, my audio problem was because the Vizio's EDID
>>> over HDMI doesn't offer a setting at the panel's native resolution,
>>> and I was overaggressively telling the driver to ignore the EDID to
>>> the point where the driver didn't think the TV had audio-over-HDMI
>>> capability.
>> ok... after this afternoon's research session, those words all make
>> sense to me, and gives me some clues for things to try should I run
>> into a similar problem.
>> Of course, the problem with the words making sense, is that now I'm
>> going to try to have the concepts make sense...
>> What do you mean by saying that " the Vizio's EDID over HDMI doesn't
>> offer a setting at the panel's native resolution"?  For the sake of
>> example, I'm going to assume that you have a 1080p Vizio (since that's
>> what I have).  Are you saying that the EDID did not report 1920x1080?
> According to the manual, the panel's native resolution is 1366x768.
> This resolution is readily available using the VGA connector.  But if
> you connect it to the computer via HDMI, that resolution is not
> reported.  You can choose 1280x720 (i.e. 720p), but in addition to
> having the TV rescale the picture, it also "helpfully" adds overscan.
> It is possible to get the native 1366x768 resolution over HDMI using a
> custom Modeline, but, as I said earlier, you have to be not too
> aggressive in telling the driver to ignore the EDID, otherwise you may
> lose audio.
I had the additional complication that I was trying to dirve both the 
VGA input and the HDMI1 input to the Vizio from the same Nvidia card as 
two separate X screens - VGA at 1366x768 and HDMI1 at 1280x720. Until I 
realized that  I needed to duplicate the  custom EDID (to eliminate the 
digital audio over HDMI) and to add a modeline for the VGA input which 
didn't provide EDID, I also ended up with what appeared to be overscan 
on the HDMI1 video input. Once I had the correct xorg.conf entries it 
all fell into place. If I had motherboard support for digital audio I 
probably would have used digital audio over HDMI thru the Nvidia card.

Hope that clarifies my situation that seems to have created confusion.


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