[mythtv-users] summary of HDMI audio problems on nvidia 190.xx drivers

[German Rodriguez]

Hi:

I just went through a couple of after work nights troubleshooting HDMI
audio on one of my frontends, the issue baffled me as I had the same
hardware and software installed in a different one that was working
ok. The only difference being that I've been using HDMI for a while on
the 2nd one and I was trying to switch from Toslink to HDMI audio on
the first one (the one with issues) because of a receiver change.
After a lot of asound.conf alsa-base.conf and such and a lot of
internet browsing through blogs and forum sites, I found out the the
nvidia 190.xx (including 190.42) drivers are known to cause issues
with HDMI audio. But my second machine was working ok with HDMI audio
and 190.42, it was in fact hard to break. Turns out that the problem
with the nvidia drivers is related to the EDID, seems like the 190
driver is unable to properly read the EDID and fails to recognize the
features, sending only a basic video signal. I went back to nvidia
185.xx.xx and everything started working fine, I took the EDID with
nvidia-settings (you have to do this on 185.xx.yy) modified X11 to use
the EDID  (which I have done a long time ago on the frontend that was
working, for a different reason, I just forgot) and updated to 190.42
to get the overscan correction feature, and everything is working ok.

As an alternate measure you can try the following option from nvidia
190.42 documentation:

Option "IgnoreEDIDChecksum" "string"

   This option forces the X driver to accept an EDID even if the checksum is
   invalid. You may specify a comma separated list of display names. Valid
   display device names include "CRT-0", "CRT-1", "DFP-0", "DFP-1", "TV-0",
   "TV-1", or one of the generic names "CRT", "DFP", "TV", which ignore the
   EDID checksum on all devices of the specified type. Additionally, if SLI
   Mosaic is enabled, this name can be prefixed by a GPU name (e.g.,
   "GPU-0.CRT-0").

   For example:

       Option "IgnoreEDIDChecksum" "CRT, DFP-0"

   will cause the nvidia driver to ignore the EDID checksum for all CRT
   monitors and the displays DFP-0 and TV-0.

   Caution: An invalid EDID checksum may indicate a corrupt EDID. A corrupt
   EDID may have mode timings beyond the capabilities of your display, and
   using it could damage your hardware. Use with care.