8-channel LPCM over HDMI

You may have heard that I've recently become somewhat infatuated with HTPCs. I've been hammering on all of the AnandTech staffers to start looking at the needs of HTPC enthusiasts, and I've personally been on a bit of a quest to find the perfect HTPC components.

Blu-ray (and HD-DVD) both support Dolby TrueHD and DTS-HD audio encoding, which offer discrete 8-channel audio output. The problem is that there's currently no way to send a TrueHD or DTS-HD encoded stream from a PC over HDMI to a receiver, the stream must be decoded on the PC. Cyberlink's PowerDVD will decode these high definition audio formats just as well as any receiver into 8-channel LPCM audio, but you need support for sending 8-channel LPCM over HDMI.

Most graphics cards that implement HDMI simply pass SPDIF from the motherboard's audio codec over HDMI, which is unfortunately only enough for 2-channel LPCM or 6-channel encoded Dolby Digital/DTS audio. Chipsets with integrated graphics such as NVIDIA's GeForce 8200 and Intel's G35 will output 8-channel LPCM over HDMI, but AMD's 780G will not.

All of AMD's Radeon HD graphics cards have shipped with their own audio codec, but the Radeon HD 4800 series of cards finally adds support for 8-channel LPCM output over HDMI. This is a huge deal for HTPC enthusiasts because now you can output 8-channel audio over HDMI in a motherboard agnostic solution. We still don't have support for bitstreaming TrueHD/DTS-HD MA and most likely won't anytime this year from a GPU alone, but there are some other solutions in the works for 2008.

To use the 8-channel LPCM output simply configure your media player to decode all audio streams and output them as 8-channel audio. HDMI output is possible courtesy of a DVI-to-HDMI adapter bundled with the card; AMD sends audio data over the DVI interface which is then sent over HDMI using the adapter.

Index NVIDIA's Unexpected Response


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  • Clauzii - Thursday, June 19, 2008 - link

    Crossfire two of that ;)

    (starts looking for a humongous PSU...)
  • rudolphna - Thursday, June 19, 2008 - link

    lol oohhh yeah.. I'll be looking for Anandtech to be reviewing PCP&Ps newest 2kW Power supply with 200amps on teh 12V rail :) Reply
  • rudolphna - Thursday, June 19, 2008 - link

    PS. (to PCP&P) Switch to 120mm fans, imagine how loud a 2000watt psu will be with an 80mm fan cooling it :) Reply
  • xsilver - Friday, June 20, 2008 - link

    the 80mm fan would require its own psu ;) Reply
  • Clauzii - Thursday, June 19, 2008 - link

    There goes the carrot cutter :)) Reply
  • Devo2007 - Thursday, June 19, 2008 - link

    I can walk into a local retailer and pick one up right now (yes, they are actually showing stock on three different cards). Reply
  • Goty - Thursday, June 19, 2008 - link

    Something is VERY wrong if a 1000W rated power supply can't boot a system that draws less than 500W at load. Most sites recommend a 500W-600W power supply to run a 4850 CF system, which should be PLENTY of power. Reply
  • Creig - Thursday, June 19, 2008 - link

    That's exactly what I was thinking when I read that part of the article. A 4850 supposedly only pulls 110w. So if I was conducting the review, I would have immediately suspected a defective power supply, not an inadequate one. Reply
  • bob4432 - Friday, June 20, 2008 - link

    exactly what i was thinking....ocz quality???? Reply
  • JarredWalton - Friday, June 20, 2008 - link

    I believe the 1000W PSU having problems was specifically in regards to GeForce GTX 280 SLI - though Anand or Derek would have to confirm. The other factor that I don't know is whether the PSU is the problem or perhaps Derek just has really bad electricity in his house. I know I've had no difficulties with even 550W PSUs and 3870 CrossFire (with a Q6600 overclocked to 3.30GHz). Reply

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