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

Calvin Harrigan charriglists at bellsouth.net
Fri Feb 20 15:09:25 UTC 2009

Michael T. Dean wrote:
> On 02/19/2009 03:32 PM, Calvin Harrigan wrote:
>> OK, disaster might be a bit strong.
>> I've been looking for good information on disabling the audio portion
>> of the video card output for almost a week.  My problem is with my new
>> video card, when I connect it to the tv it sees that it is hdmi auddio
>> capable and enables audio over the dvi->hdmi cable.  Doing so caused
>> the tv to ignore the stereo analog signal that it's being fed and try
>> to play the hdmi audio which is most times just crackling noises.  If
>> I connect my spdif output to a little connector on the video card I
>> can get audio for several applications (mythtv being one), but not
>> all, worst than that after the audio stops the crackling noises begin
>> again, especially after using xine.  I would really like to disable
>> that hdmi audio feature, but what I've found on the nvidia forums is
>> not working.
>>     I'm running Linux kernel 2.6.24 with Nvidia drivers 180.29 drivers
>> with a 9500GT (G96). Nvidia is rightfully claiming that the TV is
>> telling the driver via it's edid (Extension Block Details really) that
>> the tv has audio capabilities via hdmi. With that information I
>> downloaded my TVs edid and edited it to remove all references to
>> having audio and redid the checksums etc. X thinks the edid is fine,
>> so does monitor asset manager, but for some reasons it seems that the
>> driver still enables audio. The only way I can disable audio for sure
>> is to remove the entire Extension Block, but doing so removes several
>> of the extended supported modes that I use. Seems that the driver is
>> only looking for the presence of an extension block and is not really
>> reading into it to discern whether or not the set supports audio. I
>> can send both edids the original and the patched versions if anyone
>> would like to take a look.
>>     Anyone have similar issues/problems?  Any input would be greatly
>> appreciated, thanks.
> Got a DVI input on the TV?  HDMI->DVI cable would fix it.
> Mike
> _______________________________________________
> mythtv-users mailing list
> mythtv-users at mythtv.org
> http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users

The video card doesn't have an hdmi output, just regular vga, dvi and 
and svideo/component video.  The tv is the one with the hdmi input and 
I'm already using a dvi->hdmi cable.

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...

For the time being, I've created a custom xorg.conf based on the timings 
I got out of the edid info in monitor assest manager, no more noise and 
the tv is back to using the analog audio, it would have been nice to 
just have one cable going to the tv, but I suppose there are some bugs 
to be worked out yet.  I don't know why nvidia decided that this feature 
should be enabled by default, seems that it should have defaulted the 
other way, namely off, especially since most of the card vendors don't 
include the cable with the tiny two pin connector to connect to the 
motherboards spdif connector.


More information about the mythtv-users mailing list