AnandTech: Understanding 8-channel LPCM over HDMI: Why it Matters and Who Supports it

[shadymg]

Original Article Link

Matt, you know you shoulda written this before they did! :-P

So question....they say "(not to mention that the HDMI 1.3a spec, which enabled the streaming of these codecs over HDMI wasn't completed at the time that these GPUs were created)."

I coulda sworn that the support for the formats came in the original 1.3 (or is 1.3 original & 1.3a the same thing?)

[Matt]

Yeah it's in 1.3, they just mention 1.3a because it's the latest spec of HDMI commonly available  (1.3b isn't even worth mentioning).

[shadymg]

gotcha.

just finished reading, i'm kinda shocked (and dissapointed) they didn't cover analog distribution of the formats. i think there's a lot of people who would have benefited on that information.

[Matt]

gotcha.

just finished reading, i'm kinda shocked (and dissapointed) they didn't cover analog distribution of the formats. i think there's a lot of people who would have benefited on that information.

Yeah, I agree, however analog will always be subject to downsampling under AACS, and AnandTech's article was basically a complaint about how slow the industry has been to get the digital audio side of PC Blu-ray play back things fully AACS compliant.

[erikt]

Anyone have any details on these quotes from the article:

Every single modern day GPU today lacks support for a Protected Audio Path; that's true for the Radeon HD 4800 series, NVIDIA's GeForce GTX 200 series, and Intel's G45 GMCH.

Despite supporting 8-channel LPCM, the G45 still lacks a truly protected audio path and thus will never be able to send an encoded Dolby Digital TrueHD or DTS-HD MA signal over HDMI. I suspect that its successor in 2009 will finally add this functionality.

G45 is advertised as having PAP hardware and I've seen the option in the BIOS of my Asus P5Q-EM, but I've also seen statements like these saying that G45 will not support bitstreaming.  So, if PAP is there, what is missing?

And yes, I know it doesn't really matter since LPCM is just as good.  I'm just curious.

ET

[shadymg]

you bring up a good question, isn't LPCM the exact same as the TrueHD & DTS Master Audio, just being uncompressed & transmitted digitally?

[Matt]

Anyone have any details on these quotes from the article:

Every single modern day GPU today lacks support for a Protected Audio Path; that's true for the Radeon HD 4800 series, NVIDIA's GeForce GTX 200 series, and Intel's G45 GMCH.

Despite supporting 8-channel LPCM, the G45 still lacks a truly protected audio path and thus will never be able to send an encoded Dolby Digital TrueHD or DTS-HD MA signal over HDMI. I suspect that its successor in 2009 will finally add this functionality.

G45 is advertised as having PAP hardware and I've seen the option in the BIOS of my Asus P5Q-EM, but I've also seen statements like these saying that G45 will not support bitstreaming.  So, if PAP is there, what is missing?

And yes, I know it doesn't really matter since LPCM is just as good.  I'm just curious.

ET

Yes I know, which is why when I posted the news article I critiqued it by saying that AnandTech seems to think bitstreaming and PAP are synonymous. In theory since the G45 supports PAP, then it will be able to send LPCM un-molested with the proper player support. Unmolested LPCM should be equivallent to bitstreaming. Which is something they missed entirely. So the G45 should have a leg up over the other solutions (GeForce 8200, Radeon HD 4000 series).

Of course I could be missing something, but I don't think PAP is solely about bitstreaming, since bitstreaming shouldn't be the issue, it should be LPCM (raw, and thus pirateable audio) which is worrysome.

[autoboy]

you bring up a good question, isn't LPCM the exact same as the TrueHD & DTS Master Audio, just being uncompressed & transmitted digitally?

7.1 LPCM is different than HD audio.  You could have a standard Dolby Digital soundtrack decoded to LPCM just as easily as a HD soundtrack.  You could also have a game's soundtrack output as LPCM.  It is the transport that just so happens to also be a storage format known as uncompressed PCM.

[Matt]

you bring up a good question, isn't LPCM the exact same as the TrueHD & DTS Master Audio, just being uncompressed & transmitted digitally?

7.1 LPCM is different than HD audio.  You could have a standard Dolby Digital soundtrack decoded to LPCM just as easily as a HD soundtrack.  You could also have a game's soundtrack output as LPCM.  It is the transport that just so happens to also be a storage format known as uncompressed PCM.

Context dude, the context of this entire discussion (and the article it references) has been about Blu-ray audio. Specifically about the lossless formats (TrueHD and DTS-HD MA) versus LPCM.

[Naylia]

From a sound quality perspective there should be no difference between bitstream and 7.1 LPCM if the sample rate and bit depth are not altered after decoding. It's still a perfect digital representation of the audio being transmitted. However, I think even if the audio is just decoded and not downsampled/rezzed, there will still be a group of people demanding bitstreaming because they don't trust their pc to not alter the audio.

[autoboy]

Sorry.  Didn't read the whole article.