Understanding 8-channel LPCM over HDMI: Why it Matters and Who Supports it
by Anand Lal Shimpi on September 17, 2008 2:00 PM EST- Posted in
- GPUs
The Bandaid: The HDMI Sound Card
Ha! I lied; there's more.
No GPUs released in 2008 will support this protected audio path and thus we won't be able to get TrueHD/DTS-HD MA support from a GPU anytime soon. There is another option however: HDMI sound cards.
A couple of companies are working on sound cards with a built-in HDMI repeater, meaning there's an HDMI input, some logic to add data to the HDCP encrypted signal, and an HDMI output.
Your GPU would handle all video decoding and it would send its decoded but HDCP encrypted signal over HDMI, but instead of going to your display (or receiver or pre-processor) it would go next door to your sound card over HDMI (3dfx dongles anyone? At least these are lossless since they are digital signals... oh, hush, Monster).
The sound card would have an audio codec capable of ensuring a protected audio path and would handle all of the audio decoding/bitstreaming in the system. The audio from the sound card and the video from the HDMI input on the sound card would be combined, the HDCP repeated, and the new combined signal sent over HDMI to your receiver/display.
The HDMI spec allows for repeater support (as in devices that add something to an HDCP encrypted HDMI signal and pass along the new combined signal), so the HDMI sound card is really no different than sending HDMI to a receiver and then to your display. There should be no loss in quality or any other negative side effects if implemented properly.
ASUS and Auzentech are both working on these HDMI sound cards that should solve all of our HTPC problems. While both were supposed to be available over the summer, driver and software delays have pushed back both release dates to the last few months of 2008.
The Auzentech card
We have proof that the ASUS card was fully functional at Computex 2008; below are shots of the Xonar HDAV bitstreaming DTS-HD MA to an Onkyo receiver:
The test system
The Card
DVI to HDMI input, then HDMI output
It works!
We’ve got the ASUS card in house and are simply waiting for final drivers before testing it, so expect a review in the not too distant future.
I mainly wrote this quick guide to have something to link back to whenever I list 8-channel LPCM audio over HDMI as a feature. It’s not a typical PC feature like DirectX 10.1 or supporting SSE4, so it needed a little more of an explanation. And there you have it.
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Mastakilla - Wednesday, September 17, 2008 - link
for movies and music the sync issue can be solved on a decent receiver...the big problem is for people (like me) who also want to play games on the same system...
you cannot sync your keyboard / mouse input with a delayed sound / image!
that is the real issue for me and exactly what i would like to see some focus on in a decent (anand) article
the forum link i posted above touches the same topic...
Mastakilla - Wednesday, September 17, 2008 - link
Been waiting for something like this for a long time now...I hope the final in depth article will cover all aspects of sound on a PC (movies, music and gaming)
I have started a thread about the lack of decent information on this topic awhile ago on your forum:
http://forums.anandtech.com/messageview.aspx?catid...">http://forums.anandtech.com/messageview...amp;thre...
this includes a request to review the Auzentech soundcard toghetter with Onkyo or alike receivers as well
Hope you can make this mess a little more clear :)
thanks in advance!
Anand Lal Shimpi - Thursday, September 18, 2008 - link
I don't have the Auzentech card yet but I did just get the ASUS card in and will be working on that shortly. As soon as I get the Auzentech I'll add that to the queue :)-A
Zefram0911 - Wednesday, September 17, 2008 - link
Anyone know when this card is coming out? I've been waiting for it since it's press release in June that said this month.AnnihilatorX - Wednesday, September 17, 2008 - link
Protected path, all the bells and whistles would utterly fails at the end point. To make content viewable, ultimately you need to have it decoded. There is a weakest link between the image processor on your monitor and the HDCP chip. Surely uou can eavesdrop on the electrical signal coming from the monitor's driving circuit.Xenoterranos - Wednesday, September 17, 2008 - link
Well yes, but the mechanism to do that would be hardware based, and thus, somethign you can't download from bloorayhax.ru, which the studios are most affraid of. Remember Css? That didn't go to well for them.(Besides, this is moot. Read the above posts about AnyDVD HD: the encryption has already been broken)
Golgatha - Wednesday, September 17, 2008 - link
I'd be happy if the Cyberlink PowerDVD 8 software would just transcode the lossless audio to 5.1 DD and call it a day. Also, I wish the part of the Blu-ray spec was to require a DD track on the disc along with the lossless format.Case in point. Transformers on Blu-ray only has a TrueHD track on the disc. My HTPC cannot playback the audio in anything but stereo because of the limitations listed in this article.
The idiotic thing about this situation is even if I bought a receiver which supported TrueHD, there is no way for me to get any kind of 5.1/7.1 signal to the receiver due to the DRM implementation, lack of hardware support on the PC side, and lack of software transcoding in any commercially available playback software. Sure my PS3 can do the transcoding and I can watch Transformers with TrueHD downsampled to 5.1 DD, but my HTPC has a much better quality picture due to GPU acceleration magic. Not to mention my HTPC is a nice Blu-ray jukebox (thank you AnyDVD and yes I own the original discs), which can start the movie directly at the beginning of the movie (thank you again AnyDVD) without the ironic "don't steal our content public service message" or any previews (which are outdated and unwanted within 6months anyway and are a waste of my time).
michal1980 - Thursday, September 18, 2008 - link
i'm sorry, can you please explain to me how your htpc has a better picture then the ps3?and please make up better bs then 'gpu acceleration', becasue that is just 'bs'. The ps3 is one of the better blu-ray players on the market, and I have never seen a review mention any problems with its picture quality.
GPU acceleration is required when your CPU is too weak to playback the video, if system a is able to decode the video file, and system b is also able to, but one uses a cpu and one a gpu, then unless there is some post processing (ie changing of the final output after decoding), the picture will look the same.
also, if your reciver can play back true-hd, or dts-ma, then it can playback LPCM. and you know what the difference in sound quality between the 2 is? nearly zero. All that happens is that in the 1st case your receiver decodes the file, while in the 2nd your pc does.
fuzz - Monday, September 22, 2008 - link
well theres probably ZERO difference between htpc and ps3 when it comes to hddvd/bd, but for playing back standard dvd the htpc wins hands down (thanks to the maturity of the technology)you can get around pretty much all the quality-reduction features hollywood could come up with.
erple2 - Monday, October 6, 2008 - link
Maturity of what technology? The tech used in the PS3 for all of that is what boils down to clever software decoding. The question is simply whether the hardware on the PS3 is capable of doing all of the clever algorithmic magic to make the DVD output look good. Some "high end" (read expensive) systems do that, but they also can't put large General Purpose Processors in their components, so they use embedded systems (which are VERY inexpensive) to do the crunch work on those DVD upscale algorithms. I think that the PS3 is more than capable of doing it in software (particularly given it's nVidia G70 based GPU, plus the Cell Processor).