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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  • Final Destination II - Saturday, June 21, 2008 - link

    Btw, I have a 7600GT. I don't have to upgrade each week, because I have a display 1280x1024 display and don't care at all for 2500xquadrizillion resolutions.

    Plus, you constantly keep forgetting that the HD4850 rules in quality settings.

    Anyway. There are 5 things I will never do:
    - burn my money
    - install SLI
    - install Crossfire
    - burn my money while achieving 5% more performance ("yay! that's worth it!" says the enthusiast. "what a moron" say I...)
    - install one of those ridiculous dual-chip power burners - thanks, I already got me a nice heater for the winter.

    If you check statistics you will see that you are quite alone on your enthusiast throne, looking down on people who "only" get 85% of your performance for 33% the money.
    In fact, I would call those the "intelligent people"...
  • superkdogg - Monday, June 23, 2008 - link

    I am similar to this guy ^^^.

    I have three display options: 12x10 19" LCD monitor, 37" 720p TV, and a VGA projector. Granted the projector kinda sucks, but there's nothing quite like using the garage door as your gaming screen.

    For reason of not having a super display (nor really wanting one) having a usable video card gets really, really simple. I actually still have my x800 GTO2 flashed to x850xt and overclocked. Laugh if you want, but other than being old and not supporting newer shader models (a big deal for some, not to me) it still puts together playable framerates in many games.

    So, now that I've explained where I come from, I can say that the 4850 has my attention. I'm never going to be the $600 graphics card guy, but being the $200 graphics card guy and being able to turn up all the detail settings for most games and being 'bottlenecked' at the monitor sounds good to me.
  • Final Destination II - Saturday, June 21, 2008 - link

  • Final Destination II - Saturday, June 21, 2008 - link

    "Expect another price cut after all 9800GTX's are gone and every one is a GTX+"

    Great. That's the way to kick your own customers in the ass. Remember the price slide on the iPhone? That's what will happen to Nvidia. Frustrated 9800GTX buyers will realize that their precious $300 they bought 2 weeks ago is worth $100 less and worse than ever.

    Sorry, guy - but's that's no reason to buy another one. That's a reason to stick with it and feel sorry for each HD4850 that passes you.
  • Final Destination II - Saturday, June 21, 2008 - link

    55nm NV280? Could it be that you are confusing the 9800GTX+ with your personal wishes? Reply
  • Straputsky - Saturday, June 21, 2008 - link

    Oh, I already expected that nVidia will use the 55nm process asap. But when I look to the ATI chip (about 250mm^2) and then the nVidia (as you mentioned about 400mm^2) I still wonder if it's possible to use two of them on one board. The power consumption might be less, but I think it's still far to high.
    Have a look at the G92b. It's shrinked but due to the higher clock it uses more power than the old one. ATIs new X2 consumes a bit more power than one 280GTX and I think that's the upper end of what might be possible with air cooling. If you want to use two 280GTX you have to reduce power consumption by nearly 50%. I think that's more than you can get from the 55nm process. Maybe you can put together two 260GTX with lower clock speeds - but for which price tag? >400€? At this price level people tend to buy two 280GTX cause price doesn't matter anymore.
    Maybe you're right but until I see it, I won't believe it.
  • magnusr - Friday, June 20, 2008 - link

    Does it support 7.1 LPCM 192kHz 24bit? Good enough to disable onboard sound / audio cards?

    Tested it with receivers who supports LPCM?

    IS ATIs HDCP and drivers just as stable as Nvidia regarding connections through receivers? Had some trouble with the old 3870 while my current 9600GT works fine.
  • madgonad - Friday, June 20, 2008 - link

    Come on Derek and Anand!

    Give us gaming/HTPC lovers some info.

    What kind of audio can you get out of a BluRay?
    Will games fully utilize all seven channels, or just default to stereo?
    Are any levels of EAX supported?
    Does it have the equivalent of DD Live or DTS Connect so that games will be played in 5.1/7.1?

    These are important questions that nobody has answered due to the overwhelming infatuation with Crysis scores.

    Also, how well does it upscale DVDs? In theory that teraflop of processing power could do a lot.
  • rgsaunders - Saturday, June 21, 2008 - link

    You are wasting your time asking Anandtech to do balanced reviews with something other than gaming scores. I have tried on numerous occasions over the last several years to get them to broaden their testing, but it seems all the reviewers are adolescent gamers. They still haven't figured out that gamers are a minority of users. Reply
  • DerekWilson - Monday, June 23, 2008 - link

    we're always open to new test applications and investigative directions.

    specific suggestions will get the best results. especially if you can point us to a reliable, repeatable, fair test to use for a certain real world application.

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