HD Audio Cards( Why/Why not?)
#1
Hello Forum,

It seems that there are many opinions on the need for HD Audio capable GPU's and I notice that after reading posts that reference how to build DIY HTPC's the HD Audio option is not listed in all 7 build groups only in 6 and 7. Why?

If I were to consider building an HTPC in the near future what would be the reason to consider a GPU with HD Audio VS. a MOBO w/ a GPU that only processes 7.1 LPCM audio?

Currently I own a pre-built rig http://www.xtreamer.net/Ultra/ with this soundchip http://www.realtek.com/products/products...ProdID=284 which process HD audio tracks beautifully in my opinion but in LPCM 7.1 format. I have done side-by-side tests playing HD audio media through this rig and a rig that bitstreams HD Audio and was unable to differentiate between sound quality. So, at this moment, I do not see the need for an HTPC build with an HD Audio GPU but I'm hoping to get strong opinions on this issue as to the significance or lack thereof that may help to sway my opinion one way or the other...
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#2
Like I said in the other topic, the only difference between bitstreaming LPCM and bitstreaming codecs like TrueHD is that in the latter case the decoding to LPCM will be done by the receiver rather than by the source device.

Contrary to popular belief, a receiver is not somehow inherently better at decoding, it's probably better at doing DAC, i.e. Digital to Analogue Conversion. But this only matters when comparing analogue versus digital and LPCM and codecs like DTS/Dolby/FLAC are all digital. Hell, hdmi is digital, at least on a protocol level, so everything that is transmitted over hdmi HAS to be digital.

This means that the DAC will always be done by the receiver anyway, so that's a factor that doesn't matter. The only factor that matters is the quality of the decoder and that is much less of an art than a DAC. It's a matter of implementing specs. Also, decoding is not done by a sound card or anything, but just be the software (which can be embedded or be a lib in an OS).

Think about this: have you even heard of an mp3 decoder that, given the exact same hardware and file (so ceteris paribus), yields a better result than another mp3 decoder? No, probably not. The real differences are in the DAC (which again is not a factor in this debate) and in the amp and speakers. Decoders do or at least should not make a difference and usually they don't.

So in conclusion, it doesn't really matter in most cases. lossless = lossless. Think of TrueHD/DTS-MA/FLAC as a zipped LPCM stream.

And by the way, what do you mean with a HD capable audio card? Basically any new GPU with an hdmi out it capable of outputting LPCM and all the DTS/Dolby codecs, so for the purpose of choosing new hardware, I'd say this discussion is pretty much moot, as most hw can simply do both.
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#3
And by the way, what do you mean with a HD capable audio card?

excuse me.... when I said that I was pretty much referring to a GPU that is capable of bitstreaming HD Audio. Sorry for the noob confusion!

So, your opinion just reenforces the reasons why I cant hear a difference between formats. Good to know! Looks like I will focus on group 5 options..
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#4
NOTE: I don't know if I'm right!! Keep that in mind

I'd say in digital audio decoding, the sound card doesn't matter at all. I mean, decoding AC3 into LPCM just changes the format, but the information you'll get is the same.. It's like sending a ZIP file or a TXT file: wether you send a zip to a txt file, information is the same.

So, if you send audio to an AVR receiver or a digital audio enabled device, changing the sound card won't help, but changing the device or the speakers could.

However, if you are playing sound through analog speakers connected using the typical jacks to the sound card, then a better sound card could help.

It's like ZIP and txt.. changing the computer which decodes the file won't help, but changing the monitor may do a difference.
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#5
Correct. The most important part of a sound card (some say this is essential to being called a sound card) is the DAC circuitry. And even if it's there, it's not being used in the case of hdmi or S/PDIF.

Don't think for a moment that for instance a Geforce GT430 bears much resemblance to a 'normal' audio card or chip, even when you take away the video part. It does NOT have a DAC and it does NOT have any decoders whatsoever (a normal audio card also doesn't have decoders btw, maybe some EAX stuff, but that's not really a codec). It's not much more than a generic hdmi-controller that just happens to expose itself to the operating system as an audio card.
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