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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  • Makaveli - Friday, June 20, 2008 - link

    wow GlassHouse69,

    Do you even know what an NDA is you twit. Lets start breaking NDA's left right and center. Say goodbye to access to all this preleased hardware and the articles. I won't even mention that fact that you can get into legal trouble aswell.

  • strikeback03 - Friday, June 20, 2008 - link

    Well, the other option is to not be given any information until after the release of the hardware, as Canon did with DPReview a few times when concerned they were an early leak. Of course, they could always practice such high-level journalism as publishing rumors. Reply
  • crackedwiseman - Thursday, June 19, 2008 - link

    Is it possible that the scaling issues at 2560 x 1600 have to do with the bandwidth of the crossfire links? I have a pair of Radeon HD 3870s, and the ATI Catalyst control center notes that the cards must be connected by 2 crossfire links in order for full crossfire support of 2560 x 1600 resolutions. Reply
  • rudolphna - Thursday, June 19, 2008 - link

    Its so nice to see AMD finally competetive again. :) My next PC will feature a AMD Phenom 8450, a AMD 770 Motherboard, and a AMD Radeon 4850 :) (yes im an AMD Fanboy sue me lol) Now they just need to get the Phenom clock speeds up and they will be back to full competiveness. This is a good sign, keep it up AMD! =D Reply
  • anindrew - Thursday, June 19, 2008 - link

    Very well written article. I liked how you poked fun at the fact that you couldn't give all the details about the card. At first, I felt that you were being a bit pro-Nvidia, but as I continued reading, it was very clear that you were being objective by letting the numbers (FPS) do the talking. You even compared their market strategies!

    The 4850 for $199 is an incredible price/performance ratio. As someone who is getting ready to build a new PC in the next few weeks, I was extremely interested to see this article. Considering how well the 4850 performs, I'm really interested to see how the estimated $299 4870 will perform. Hopefully, it will have a similar price/performance ratio.
  • Clauzii - Thursday, June 19, 2008 - link

    It was a long march towards this for AMD/ATI. The comming together. The whole Crossfire stuff with cables etc. The 'not so good as expected 2900XT' etc. Paperlaunches. Seems they are getting into shape. Let's see what COU's AMD comes up with, to pair these beasts.

    I especially loved the straight line at the 60FPS-limit in AC. Brilliant, considering every other card was at a falling slope :)) And the more than 100% scaling in COD4. Believe me, I'll be in shock even after sending this comment :O

    OK, two 4850 cards for what I would have paid for one card 6 months ago haven't I waited? Allright!!
  • Clauzii - Thursday, June 19, 2008 - link

    COU's???? What was I seeing :-/

    "CPUs", of course :)
  • Pottervilla - Thursday, June 19, 2008 - link


    Running GPU-Z we see that the Radeon HD 4850 shows up as having 800 stream processors, up from 320 in the Radeon HD 3800 series. Remember that the Radeon HD 3800 was built on TSMC's 55nm process and there simply isn't a smaller process available for AMD to use, so the 4800 most likely uses the same manufacturing process. With 2.5x the stream processor count, the RV770 isn't going to be a small chip, while we can't reveal transistor count quite yet you can make a reasonable guess.

    So much for not telling us--your GPU-Z screen shot says 55nm right on it. :)
  • gochichi - Thursday, June 19, 2008 - link

    Until new games come out, I see no reason to have more than one HD 4850 card. (The obvious exception being having a 30" ultra-high res LCD, which is kind of nutty when you could have a 32" 1080P HDTV for gaming, or one of the awesome 24" LCDs for a handful of bills.) I am really excited about AMD's continued improvements on the HDMI audio, I think HDMI is absolutely the best way to deliver audio in the future and AMD is making it really hard to select any other company if you're planning on connecting your computer to an HDTV. MY computer monitor supports HDMI, and then I can just connect headphones to it which is really nice because it prevents clutter. Why the heck would you get a pricey Sound Blaster when you can just use one simple solution for all of it (not that I believe in sound cards, I think they've been silly for 5+ years).

    The performance is really spot on, it really fits the consumer's needs. I still don't think that given the number of games out and the great performance of a 8800GT or even an HD 3870 there would be too much reason to upgrade. I'm a hypocrite though, because my mouth waters at the difference in COD4 at 1200P between my HD 3870 and HD 4850... though I simply don't use 4X AA (I disable AA). If I were buying today, I think I'd choose the HD 4850 at $200 over the 3870 at $130.00 but it's just because the 4850 is so likable (it's unpretentious, single slot, feature rich).

    Because there is "no need" for these products, AMD is right to price these things at $200.00 and not at $650.00. NVIDIA is really dropping the ball IMHO though their price drops on old tech will protect them for a bit, the total lack of 10.1 support, the lack of awesome HDMI audio (AMD now has the best available on the PC it sounds like) and a less complete video decoder than AMD all make NVIDIA simply uncompetitive at this point. Why do with less features for the same performance?

    The other thing is that when you're talking $150 vs $200, people are going to just go for a nice HD 4850. Now, $200 to $650??? Well... I just don't think that the games nor the CPUs are out yet that would merit this expense.

    Let's see... COD4 is still the best game on the PC and it runs fantastic on the HD 4850. Crysis is a benchmark (that still porks out every single configuration you throw at it IMHO). The 8800GT and now the HD 4850 are important as well because these cards give PCs room to outperform the PS3 and XBOX 360 even at 1200P (1920x1200) when compared to the consoles' 720P. There is absolutely no PS4 generation console on the horizon. These cards now ensure that PC gaming is affordable to everyone interested and put PC gaming in the most affordable place I've ever seen it in my life. Absolutely never could you have a near perfect video card (given the games in the market, and the highest resolution displays) for $200.00 (though the 8800GT was an exception during the week it launched).

    This is really an exciting release, I can't fathom picking up a console right now. CPU's are so nice and cheap, as is RAM, and now these cards, it's just great. NVIDIA: $700-800 is the target price FOR THE WHOLE gaming PC, not just the video card, get it right.
  • Forbin Rhodes - Thursday, June 19, 2008 - link

    I can't wait until ATI comes out with the 4870 X2. I think NVIDIA can throw their TRI SLI in the dustbin? Reply

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