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.

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  • pwnedbygary - Sunday, July 06, 2008 - link

    This card is absolutely a BEAST at folding. Now that standford U. has released the GPU2 Client for XP/2003 (im running it on Vista however) it can complete a 10,000,000 piece workunit in about 2-3 hours. I'd like to see the PS3 do THAT hehe.

    Heres a screenshot: http://i47.photobucket.com/albums/f198/pwnedbygary...">http://i47.photobucket.com/albums/f198/pwnedbygary...
    Reply
  • marone - Tuesday, June 24, 2008 - link

    ATI to Nvidia: Im at ur base, ste@ling your customers Reply
  • Matrixfan - Tuesday, June 24, 2008 - link

    Hello! Please excuse me if it is obvious, but what kind of fps figures are in the test? Do these figures represent minimum or average fps numpers? Reply
  • flexy - Monday, June 23, 2008 - link

    truly, truly amazing. A high-end card which you can get or $149 at BB.

    NV..eat this. I applaud AMD this time after some years of disappointment since we didnt see anything exciting after 9700/9800...but this card will be a killer. Price/Performance is actually unreal.
    Reply
  • jamstan - Monday, June 23, 2008 - link

    I find it odd that a 1000watt OCZ power supply wasn't big enough when the manufacturers only recommend a 550watt PSU for 2 4850s in CF? Sounds like that 1000watt PSU has a bad rail or something. Reply
  • HOOfan 1 - Monday, June 23, 2008 - link

    It is complete HOGWASH.

    As I stated elsewhere, the card can pull NO MORE THAN 75W from the PCI-E socket and NO MORE THAN 75W from its single 6pin PCI-E connector. Two of them can draw no more than 300 Watts. The OCZ EliteXstream uses a single 12V rail so there can be no excuses of over current shutting the PSU down. The PSU is also good for another 660Watts of 12V power....that could power a few peltiers and tons of fans and Harddrives.

    It is sad to think that some people will read this article and actually believe they need a $200+ 1200W PSU to run dual HD4650, when a $100 Corsair VX550 would do.
    Reply
  • solog - Monday, June 23, 2008 - link

    Why would the manufacturers claim 550W if it were nowhere near enough? Derek Wilson stated that the load draw wasn't stressing the cpu, ram and hard drive. But if you factor those in they still aren't anywhere close to 1000 watts (or the 1200 watts that they claim is really needed to run it!)


    Maybe someone else should redo the power consumption test with different power supplies, including 550W units that are known to be functional. Anyone else see any review that claims anything like this?
    Reply
  • BigDaddyCF - Monday, June 23, 2008 - link

    Yes you could sat that
    "While it is true that two RV770s can outperform a single GT200 in many cases, you could also make the argument that two GT200s could outperform anything that AMD could possibly concoct."
    However concocting that dual GT200 solution will cost you
    $640 x 2 = $1280
    that's what I'd call the lunatic fringe of gamers, and it has to be a small portion of the market.
    Reply
  • jhb116 - Sunday, June 22, 2008 - link

    For the official review - can we get the real sound numbers? Also - with the power - is the 4850's power saving features enabled?

    I'm also looking for this type of info when you get the GTX+ review(s). Is any further info on the Hybridpower features - last time I read - it seemed this feature wasn't working?

    Could be game changing for either competitor if they got this type of feature to work. I'm willing to sacrifice a bit of performance to keep my system somewhat green during downtime/web surfing.
    Reply
  • Bobattack - Sunday, June 22, 2008 - link

    While this is a preview of the 4850 and I'm sure a lot of us can't wait to see how well the 4870 will compare. The test scores don't match up between THIS review (June 19) and the GTX 280 review (June 18) but your hardware stats are exactly the same.

    Bioshock 1920x1200

    Card 08.18 08.19 (ATI 4850 preview)
    GTX 260 69.0 50.4
    9800GTX 64.6 42.3
    ATI 3870 64.6 41.0

    But I looked at the chart again and noticed the problem while typing this.

    The WRONG screen res. is in the grid! (Also some numbers don't match from the BASIC chart to the detailed multi res chart)
    So you have 1280x1024/ 1600x1200 / 1920x1200, which wrong.
    It should be 1600x1200 / 1920x1200 / 2560 x 1600!

    Its a preview, and it was kind of last minute, so its understandable.
    Reply

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