Scenario 4: Nvidia videocard with HDMI
Nvidia’s audio-over-HDMI options are more limited than AMD’s. Most videocards based on new Nvidia GPUs (e.g., the GeForce 8000- and GT 200-series) support HDMI via an adapter and many have a S/PDIF input, so you can transfer both digital video and digital audio over a signal HDMI cable.
But if you’re not using a motherboard with an Nvidia chipset (e.g., nForce 750i, 790i, or 780i), you might not have the S/PDIF output header needed to make this connection. Even if your motherboard does have it, the card is capable of receiving only two channels of digital audio that can be sent over the HDMI cable—you can’t get any form of surround sound over HDMI this way, much less Dolby TrueHD or DTS-HD.
Here’s yet another solution for integrating your PC’s audio capabilities into your home-theater system: Use an external USB audio device. These won’t deliver multichannel sound over HDMI, but they’re dead simple to install: Plug the device into your PC’s USB port with one cable, plug it into your A/V receiver with another, and install the accompanying software.
Asus’s Xonar U1 USB Audio Station ( www.asus.com ) and Creative’s X-Fi Surround 5.1 ( www.creative.com ) are two examples of external USB audio devices. Both products use Dolby Digital Live to encode any audio signal to 5.1-channel Dolby Digital in real time. The audio is then output through a S/PDIF interface to your A/V receiver.