If you want to take full advantage of your PC’s audio potential, you should connect your rig to your A/V receiver and passive speakers—or a really good set of powered speakers. But accomplishing this task is often tricky, thanks to a combination of digital rights issues, proprietary surround-sound algorithms, and evolving connection standards.
Computers outfitted with Blu-ray drives and certain late-model videocards can deliver Blu-ray video over HDMI, but getting HD audio that way is another issue. An HDMI cable can carry both high-definition video and up to eight channels of high-definition audio (front left and right, front center, rear left and right, side left and right, and low-frequency effects). Blu-ray discs are typically encoded using Dolby TrueHD, DTS-HD, or DTS-HD Master Audio; all three of these eight-channel lossless compression codecs can deliver bit-for-bit perfect copies of the original movie soundtrack. Here lies the rub: PCs currently cannot output audio encoded in any of these formats over HDMI.
A properly outfitted PC running CyberLink’s PowerDVD 8, however, can decrypt and decompress Dolby TrueHD and DTS-HD and output it as uncompressed eight-channel LPCM (linear pulse code modulation) to HDMI. However, while videocards based on newer Nvidia GPUs are outfitted with HDMI, they’re all limited to two-channel LPCM (linear pulse code modulation) audio over HDMI, and that’s only if your motherboard has a S/PDIF-out header.
AMD’s RV7xx-series cards can deliver uncompressed eight-channel LPCM audio over HDMI because they route the signals over the PCI Express bus. For integrated graphics, motherboards with Nvidia’s GeForce 8300 chipsets (for AMD CPUs) and GeForce 9300 or GeForce 9400 chipsets (for Intel CPUs), and those with Intel’s G35 Express, G45 Express, and G965 Express chipsets can do it, too.
We highlight the four most common PC audio scenarios. Pick the one that fits your situation and we’ll show you the best way to integrate your PC into your home-theater system.
Dolby Digital Live (part of the Dolby Home Theater application suite) and DTS Connect are both real-time encoding technologies. Dolby Digital Live converts any audio signal, including 5.1 sound from games, into a Dolby Digital bitstream (containing 2.0, 5.1, or 7.1 channels) in real time. That bitstream is output over a S/PDIF connection to your A/V receiver.
Your receiver decodes the bitstream and converts it into an analog signal that can be amplified and played through your speakers. You’ll find Dolby Digital Live support in all Intel Express chipsets that support Intel High Definition Audio, going as far back as the Intel 915 Express.
DTS Connect consists of two DTS technologies: DTS Neo:PC and DTS Interactive. The former takes two-channel audio and converts it into a matrix of up to 7.1 channels; the latter encodes digital audio sources into DTS Digital Surround, which you can output to your A/V receiver using a S/PDIF cable. DTS Connect isn’t as common as Dolby Digital Live, but it is supported by many onboard audio chips (including Realtek’s ALC889A).
Most motherboard manufacturers rely on either the Windows Control Panel or whatever software their audio codec supplier has come up with to serve as a user interface for enabling multichannel sound. In the Windows Control Panel, for instance, you simply drill down into the sound control panel and choose either a 5.1 or 7.1 speaker configuration.
If you’re rolling with a Radeon HD 4600- or 4800-series GPU, you can connect a DVI-to-HDMI adapter to your card and send digital video and 7.1-channels of uncompressed digital audio to your A/V receiver over a single HDMI cable. A DVI-to-HDMI adapter should have been included with your videocard. If it wasn’t, or you’ve lost it, you can purchase a replacement for about $10; just make sure that it’s certified to work with your card.
As we mentioned in the introduction, you can’t send Dolby TrueHD or DTS-HD over this HDMI connection. And you’ll need a software Blu-ray player that’s capable of decoding these audio codecs to LPCM (CyberLink’s PowerDVD 8 is the only program we are aware of at press time that can do this).
Be aware that some videocard manufacturers support the adapter on only one of the card’s DVI ports. Some other manufacturers provide an HDMI port right on the mounting bracket—a preferable solution considering that the adapter adds 1.75 inches of depth to the back of your PC. This can be a problem if you’re integrating your PC into your entertainment center.
Once you’ve plugged the HDMI cable into the videocard, open the Windows XP Control Panel (switch to Classic View if that’s not your default), double-click Sounds and Audio Devices, click the Audio tab, and choose Digital Output Device (HDMI) as the default device. If you’re running Vista, open the Control Panel, switch to Classic View, double-click Sound, right-click Digital Output Device (HDMI) and choose the option Set as Default Device from the pop-up menu.
There is currently no way to get audio—be it digital or analog—from an add-in soundcard into a Radeon HD videocard.
In each of these scenarios, there are situations in which the best solution is to connect your PC’s or soundcard’s discrete analog outputs to your A/V receiver’s multichannel inputs. This adds to cable clutter, but it solves the Blu-ray HDMI problem if you don’t have a videocard that’s capable of sending more than two channels of LPCM audio over 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.