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http://we.pcinlife.com/redirect.php?tid=1259597&goto=lastpost
O+ a+ o9 z' v# ?http://www.anandtech.com/video/showdoc.aspx?i=3643&p=10 , |: d o6 F2 X1 I; @6 W) J
+ A& r. |5 _, y/ f4 L8 E) aThe Race is Over: 8-channel LPCM, TrueHD & DTS-HD MA Bitstreaming
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It's now been over a year since I first explained the horrible state of Blu-ra4 z" N; Y& i# g" r4 t
y audio on the PC. I'm not talking about music discs, but rather the audio com
- T# f6 J/ e% I8 A4 a* cponent of any Blu-ray movie. It boils down to this: without an expensive sound% Z6 [8 Z9 x' i
card it's impossible to send compressed Dolby TrueHD or DTS-HD Master Audio s: j* v6 C3 {5 C& ?
treams from your HTPC to an AV receiver or pre-processor. Thankfully AMD, Inte t; N2 X2 Q% m0 v" O
l and later NVIDIA gave us a stopgap solution that allowed HTPCs, when equippe
* R8 U! C. m5 O' A( ld with the right IGP/GPU, to decode those high-definition audio streams and se
4 j3 R z! P6 w. k4 Wnd them uncompressed over HDMI. The feature is commonly known as 8-channel LPC+ ]) ~( { n3 z g0 m4 K& p
M support and without it all high end HTPC users would be forced into spending
, [! [" z( ?5 P1 K0 q& d- f# J. {another $150 - $250 on a sound card like the Auzentech HomeTheater HD I just ; p- D* K" K: n" S. L( ]# Y
recently reviewed.
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. t' v8 X$ _. h; M0 a. bFor a while I'd heard that ATI was dropping 8-channel LPCM support from RV870 ; L" R7 y' F# \7 k% e2 ?$ F3 t& K s
because of cost issues. Thankfully, those rumors turned out to be completely u* ?$ @" b% p' ~0 B2 d" m
ntrue. Not only does the Radeon HD 5870 support 8-channel LPCM output over HDM- J; P2 G+ z: r2 z8 r
I like its predecessor, but it can now also bitstream Dolby TrueHD and DTS-HD
, f$ z% e' @( n( aMA. It is the first and only video card to be able to do this, but I expect ot: H+ } P8 q5 S% G- ~
hers to follow over the next year.
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2 [( v" J. [& ^8 G8 p' MThe Radeon HD 5870 is first and foremost a card for gamers, so unless you're b
1 x1 T! M, P6 p5 b. vuilding a dual-purpose HTPC, this isn't the one you're going to want to use. I
- T3 e& f1 Q6 If you can wait, the smaller derivatives of the RV870 core will also have bitst
# r9 R# U4 H& M# \! N" x( kreaming support for TrueHD/DTS-HD MA. If you can't and have a deep enough HTPC
7 Z' I9 B. ]7 G* Scase, the 5870 will work. 0 D8 G8 z! c6 Q( X$ U
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In addition to full bitstreaming support, the 5870 also features ATI's UVD2 (U
7 j8 t0 x- g' T! A5 |- V6 aniversal Video Decoder). The engine allows for complete hardware offload of al
* b0 z1 Y3 d: A+ E+ Vl H.264, MPEG-2 and VC1 decoding. There haven't been many changes to the UVD2 9 ]6 o H$ A1 o. N5 e
engine; you can still run all of the color adjusting post-processing effects a
4 S' \. L7 z- P$ [- _nd accelerate a maximum of two 1080p streams at the same time.3 }9 }- H7 H$ R* \# u b5 I( B
1 G0 T* p; }3 d$ Y' m: iATI claims that the GPU now supports Blu-ray playback/acceleration in Aero mod
2 F* K& i: z+ J# L5 s' x$ R* K+ l! t0 ce, but I found that in my testing the UI still defaulted to basic mode.
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3 }8 n, C/ h. i' ZTo take advantage of the 5870's bitstreaming support I had to use a pre-releas
# W/ e' O/ g9 re version of Cyberlink's PowerDVD 9. The public version of the software should
0 S/ t- [: X" B! ` abe out in another week or so. To enable TrueHD/DTS-HD MA bitstreaming you hav
8 K9 i, K, m4 M9 N1 ^7 De to select the "Non-decoded high-definition audio to external device" option
# V. `* }! g5 s% u1 w {$ jin the audio settings panel:
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With that selected the player won't attempt to decode any audio but rather pas
+ B( y: `- D- n) @+ D9 [$ \s the encoded stream over HDMI to your receiver. In this case I had an Integra
2 B- _" d1 H! J! z/ ^ y" B v1 kDTC-9.8 on the other end of the cable and my first test was Bolt, a DTS-HD MA
- F4 O% Y+ n# z! @9 t4 x. z% M/ ftitle. Much to my amazement, it worked on the first try:0 e* ?& J: E, ^! t) l' I
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No HDPC errors, no strange player issues, nothing - it just worked.
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% A( n/ a1 w& I. ~4 c5 I8 xNext up was Dolby TrueHD. I tried American History X first but the best I coul
6 g" P4 l4 h: \1 B0 @d 【请注意文明用词】 of it was Dolby Digital. I swapped in Transformers and found the sam" F2 a$ O9 c& K# `: y- C
e. This ended up being an issue with the early PowerDVD 9 build, similar to is% ~# U$ k4 s$ e+ u0 h* Y6 c
sues with the version of the player needed for the Auzentech HomeTheater HD. S ]( l& y8 @8 V8 o& H
witching audio output modes a couple of times seemed to fix the problem, I now1 `% ?3 i0 |) ^; X% C
had both DTS-HD MA and Dolby TrueHD bitstreaming from the Radeon HD 5870 to m
" W& u5 M* Y( Y/ b$ ?3 k" By receiver.3 n( d$ I- c! H+ f/ D7 U
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One strange artifact during my testing was the 5870 apparently delivered 1080i" w. Q( S8 H& Y' s
output to my JVC RS2 projector. I'm not exactly sure what went wrong here as ) z- ^+ B2 g& c6 I/ o
1080p wasn't an issue on any other display I used. I ran out of time before I
5 S: B" ]8 ^- J# M: Qcould figure out the cause of the problem but I expect it's an early compatibi. ?( n" H9 y6 p: u5 n, c1 a
lity issue. - H! B; M l5 C1 t ?6 g
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I can't begin to express how relieving it is to finally have GPUs that impleme
4 }" p: O' _% `8 z+ B. \7 Ynt a protected audio path capable of handling these overly encrypted audio str; e n; q% O/ m
eams. Within a year everything from high end GPUs to chipsets with integrated 8 ?# ]# u4 V( Q% z
graphics will have this functionality. |
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发表于 2009-9-22 14:33
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