[mythtv-users] HDMI and audio

John Finlay finlay at moeraki.com
Thu Nov 19 05:30:58 UTC 2009

Patrick Doyle wrote:
> I am curious and confused (yet again) however... what is it about your
> motherboard that inhibited the use of "digital audio over HDMI thru
> the Nvidia card"?
> As I understand it, (and I'm making some of this up), the driver for
> the nVidia card should provide an audio output device for alsa to use.
>  MythTV should be able to make use of that audio output device instead
> of whatever (real) audio output device is on your motherboard.  It
> should be able to route the (digital) audio samples directly to that
> device.
> I spent a fair amount of this afternoon confused by (possibly a single
> posting) that referenced some sort of cable that would connect from
> the motherboard to an audio pass-thru port on the video card.  But
> since HDMI is all digital, I think that the driver for an HDMI video
> card should provide a virtual input spigot into which SW can scribble
> audio samples to be transferred to the TV.  At this point, I have no
> idea what format those samples are (16 bit PCM, 48kHz comes to mind,
> but they could just as easily be a compressed MP3 stream).
My Nvidia card (8500GT) has a 2-pin molex connector on it that can be 
used to cable to a digital audio output connector on the MB (or a 
soundcard I presume). As I understand it the digital audio signal can 
then be directed thru the DVI connector and DVI-HDMI adapter to the HDMI 
input in the TV. Since I don't have a soundcard or MB with this 
connector I can't use this mechanism. It does sound logical that a 
different Nvidia card could have some digital audio capability built-in 
so no jumper cable is needed but that is outside my experience.


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