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http://we.pcinlife.com/redirect.php?tid=1259597&goto=lastpost2 \* T1 O- J( ^: Q* E
http://www.anandtech.com/video/showdoc.aspx?i=3643&p=10 ! e+ l$ Z! s1 y/ M/ H- k& x
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The Race is Over: 8-channel LPCM, TrueHD & DTS-HD MA Bitstreaming
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. y# \6 S* }) g9 _- l% X) g5 lIt's now been over a year since I first explained the horrible state of Blu-ra! K- ?$ p6 ]& G7 T
y audio on the PC. I'm not talking about music discs, but rather the audio com/ ]; `+ c% S) c
ponent of any Blu-ray movie. It boils down to this: without an expensive sound8 A. X8 i0 A; h. H
card it's impossible to send compressed Dolby TrueHD or DTS-HD Master Audio s$ b+ j) ^' O' ?' t2 C: B# I" w
treams from your HTPC to an AV receiver or pre-processor. Thankfully AMD, Inte! [& p2 y9 ?) p
l and later NVIDIA gave us a stopgap solution that allowed HTPCs, when equippe% ^+ k6 A. [7 @" g
d with the right IGP/GPU, to decode those high-definition audio streams and se
6 ~5 }# @% Y$ K/ und them uncompressed over HDMI. The feature is commonly known as 8-channel LPC
* s7 [! k; C7 @. iM support and without it all high end HTPC users would be forced into spending
$ h4 u# J9 P' v. v" M3 ranother $150 - $250 on a sound card like the Auzentech HomeTheater HD I just
/ b! w; c& I7 g/ yrecently reviewed.
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( {" R2 t! }' n: A9 B- A rFor a while I'd heard that ATI was dropping 8-channel LPCM support from RV870 6 L! z/ c, p, y
because of cost issues. Thankfully, those rumors turned out to be completely u
) N2 T# W4 j5 t9 U0 s5 _ntrue. Not only does the Radeon HD 5870 support 8-channel LPCM output over HDM7 T* ]" K P: m: a, e
I like its predecessor, but it can now also bitstream Dolby TrueHD and DTS-HD
, B! b U/ C+ N1 q0 O' CMA. It is the first and only video card to be able to do this, but I expect ot
, b4 J5 r) E+ V8 U: ]hers to follow over the next year. 9 j5 T, ~1 U+ s, c7 Y: ^8 q
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The Radeon HD 5870 is first and foremost a card for gamers, so unless you're b8 M/ D/ t+ d+ h2 f4 m! Q3 |
uilding a dual-purpose HTPC, this isn't the one you're going to want to use. I
! p0 n6 _% K# N% w: k" cf you can wait, the smaller derivatives of the RV870 core will also have bitst1 R- y o3 r$ Q- y7 d& }
reaming support for TrueHD/DTS-HD MA. If you can't and have a deep enough HTPC
' O) K- s$ N1 Y$ m% y: N# U4 G- `case, the 5870 will work. + s. B; ~( j/ x5 a! `
* R- c+ \* y, T: L1 I3 \: vIn addition to full bitstreaming support, the 5870 also features ATI's UVD2 (U0 T9 u' @+ D& r2 S" C. E
niversal Video Decoder). The engine allows for complete hardware offload of al
4 ]& N8 A) N4 y% Wl H.264, MPEG-2 and VC1 decoding. There haven't been many changes to the UVD2 / D- V# H4 M2 i7 o
engine; you can still run all of the color adjusting post-processing effects a
1 {. @- ^! C( G4 And accelerate a maximum of two 1080p streams at the same time.
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ATI claims that the GPU now supports Blu-ray playback/acceleration in Aero mod
3 i" ~9 |; M$ N7 f3 u: Pe, but I found that in my testing the UI still defaulted to basic mode.
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To take advantage of the 5870's bitstreaming support I had to use a pre-releas
6 w+ m0 d! ~# W( v) te version of Cyberlink's PowerDVD 9. The public version of the software should
3 E; d/ U5 h& c1 y( G$ R/ \& zbe out in another week or so. To enable TrueHD/DTS-HD MA bitstreaming you hav
" t$ n4 G0 W' N# re to select the "Non-decoded high-definition audio to external device" option ' v5 |- i& \& q# f
in the audio settings panel:8 n) Q5 n; t8 j( Z% U4 q. C
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With that selected the player won't attempt to decode any audio but rather pas
1 H& y7 ?8 H/ `- d6 M& z3 xs the encoded stream over HDMI to your receiver. In this case I had an Integra h; m+ z/ E `( w' N+ |* n
DTC-9.8 on the other end of the cable and my first test was Bolt, a DTS-HD MA* ?: V2 Z) F" }: `( w
title. Much to my amazement, it worked on the first try:
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3 w1 V+ R8 F# _' Z0 g% @" LNo HDPC errors, no strange player issues, nothing - it just worked.
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Next up was Dolby TrueHD. I tried American History X first but the best I coul
* f, S# {! |9 R: Wd 【请注意文明用词】 of it was Dolby Digital. I swapped in Transformers and found the sam8 ]2 ~5 h r7 T1 x& S
e. This ended up being an issue with the early PowerDVD 9 build, similar to is
" R# F4 N* I Fsues with the version of the player needed for the Auzentech HomeTheater HD. S
6 W/ [% s9 f# u+ A3 i, W/ a( o6 Rwitching audio output modes a couple of times seemed to fix the problem, I now+ v* p I# `& L" X o0 e
had both DTS-HD MA and Dolby TrueHD bitstreaming from the Radeon HD 5870 to m
4 j: B* q R2 }; @; @7 Sy receiver.
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& {/ n1 _8 R4 j n# X& ]: wOne strange artifact during my testing was the 5870 apparently delivered 1080i
+ }& q' s7 E; \output to my JVC RS2 projector. I'm not exactly sure what went wrong here as
! `# G; b7 `: C& L8 E* C1080p wasn't an issue on any other display I used. I ran out of time before I
# V5 D# U3 r0 {, q& f' E( k0 Mcould figure out the cause of the problem but I expect it's an early compatibi
/ U9 d: Y( G9 j H& [lity issue.
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I can't begin to express how relieving it is to finally have GPUs that impleme
- r; p. ~* D) u2 b! A8 N/ x. R1 [nt a protected audio path capable of handling these overly encrypted audio str
1 ?% v) R# S6 Aeams. Within a year everything from high end GPUs to chipsets with integrated 8 c: Q# c! w* \% \0 c
graphics will have this functionality. |
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发表于 2009-9-22 14:33
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