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http://we.pcinlife.com/redirect.php?tid=1259597&goto=lastpost
+ h* c3 P6 y/ i2 _7 f, ]http://www.anandtech.com/video/showdoc.aspx?i=3643&p=10 ' a' O: `' q2 r# q" S9 O) K
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The 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-ra! W( G& M1 \3 X4 g q
y audio on the PC. I'm not talking about music discs, but rather the audio com) t3 }2 [ Z" V) C$ e/ |; ^0 e3 y& c- K
ponent of any Blu-ray movie. It boils down to this: without an expensive sound s% g- {( _$ I4 ]
card it's impossible to send compressed Dolby TrueHD or DTS-HD Master Audio s3 U6 ]) D1 V$ Y0 }6 \
treams from your HTPC to an AV receiver or pre-processor. Thankfully AMD, Inte G: u% n; y& G
l and later NVIDIA gave us a stopgap solution that allowed HTPCs, when equippe
; c& U& k3 l b: p( c" s k% c, Ld with the right IGP/GPU, to decode those high-definition audio streams and se
0 p& I. S: B; ^. q* s7 rnd them uncompressed over HDMI. The feature is commonly known as 8-channel LPC7 \3 Z* x( L! S
M support and without it all high end HTPC users would be forced into spending2 r: T6 K! @& C" ]3 P) k- A
another $150 - $250 on a sound card like the Auzentech HomeTheater HD I just
$ _* l/ d! \/ ]% u1 _( W T6 mrecently reviewed. 4 |0 ~0 R& k s) u
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For a while I'd heard that ATI was dropping 8-channel LPCM support from RV870 % o# c$ j( E, _* m% m# v- m
because of cost issues. Thankfully, those rumors turned out to be completely u
) @- p$ c" |2 N, i- S2 w: |ntrue. Not only does the Radeon HD 5870 support 8-channel LPCM output over HDM- f& C( ^6 S3 b1 P& u+ F4 p1 _
I like its predecessor, but it can now also bitstream Dolby TrueHD and DTS-HD & l" m& Y! w' ?) [
MA. It is the first and only video card to be able to do this, but I expect ot, ^6 M( P# c; I8 @# V5 a
hers to follow over the next year.
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! `# W$ ^0 ~# |. A+ OThe Radeon HD 5870 is first and foremost a card for gamers, so unless you're b
/ _" b8 b/ Y; c$ s4 I: huilding a dual-purpose HTPC, this isn't the one you're going to want to use. I
9 l1 G2 N8 Z; N" @ kf you can wait, the smaller derivatives of the RV870 core will also have bitst1 h: s0 {% w* S: h
reaming support for TrueHD/DTS-HD MA. If you can't and have a deep enough HTPC6 I8 A( u3 t! \
case, the 5870 will work.
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' _2 e& t. Q) {1 ~7 }0 v3 QIn addition to full bitstreaming support, the 5870 also features ATI's UVD2 (U L7 r- O o# c9 v
niversal Video Decoder). The engine allows for complete hardware offload of al/ l6 _, s( S) b9 S* A* ]
l H.264, MPEG-2 and VC1 decoding. There haven't been many changes to the UVD2
7 c5 F% V# n1 d0 ]4 n- [2 A& o: Nengine; you can still run all of the color adjusting post-processing effects a- h0 i' `5 `5 B v4 Q; [9 k5 f
nd accelerate a maximum of two 1080p streams at the same time.5 g) i0 I+ n" ]. k( X; Q0 f
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ATI claims that the GPU now supports Blu-ray playback/acceleration in Aero mod' `9 T' v/ A; a: A
e, but I found that in my testing the UI still defaulted to basic mode.
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3 B8 o6 a { z9 tTo take advantage of the 5870's bitstreaming support I had to use a pre-releas
1 N+ z5 D9 i, {e version of Cyberlink's PowerDVD 9. The public version of the software should
s0 g+ E; R7 w7 H, v, g1 Y, tbe out in another week or so. To enable TrueHD/DTS-HD MA bitstreaming you hav
0 p/ ]( {( S, E+ b x' M$ pe to select the "Non-decoded high-definition audio to external device" option
! h. p' P" p/ @; X) u% min the audio settings panel:+ ?1 q6 K, r4 d6 z9 q
. {5 }: R# S) o- F8 R( X5 H: }, VWith that selected the player won't attempt to decode any audio but rather pas4 w- \, K8 m( i9 c4 Z. `) _
s the encoded stream over HDMI to your receiver. In this case I had an Integra5 E6 r; W' h2 K& J5 N, Y" w- F
DTC-9.8 on the other end of the cable and my first test was Bolt, a DTS-HD MA
0 s! u7 D6 [5 n8 O, K" |title. Much to my amazement, it worked on the first try:0 e6 b) q* w# d7 t: U* S/ d" R
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No HDPC errors, no strange player issues, nothing - it just worked. " W0 @. ^; D4 W4 X E! w
" d( X' I# z" lNext up was Dolby TrueHD. I tried American History X first but the best I coul2 f3 H9 \5 x, h, B
d 【请注意文明用词】 of it was Dolby Digital. I swapped in Transformers and found the sam' D$ W- a8 [# F8 |
e. This ended up being an issue with the early PowerDVD 9 build, similar to is
+ `5 u& N$ T% s$ `' Xsues with the version of the player needed for the Auzentech HomeTheater HD. S8 ]5 y# k9 w( z2 v( o1 ]1 G( W
witching audio output modes a couple of times seemed to fix the problem, I now
) Q. F$ [% m: s' s$ W( Vhad both DTS-HD MA and Dolby TrueHD bitstreaming from the Radeon HD 5870 to m) j9 s2 ^" h& @. i0 H0 A2 {9 E
y receiver.
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) l( m4 j) y7 FOne strange artifact during my testing was the 5870 apparently delivered 1080i' N" V$ b' h1 C. T" F u
output to my JVC RS2 projector. I'm not exactly sure what went wrong here as 4 s% h* h G: N8 i
1080p wasn't an issue on any other display I used. I ran out of time before I
/ J' b5 V, m6 I8 _could figure out the cause of the problem but I expect it's an early compatibi# i( O. S$ k5 D6 n
lity issue. 9 H- z, X# s( v; ], m1 s1 t/ b
+ X9 H9 z1 s+ W7 i" {" vI can't begin to express how relieving it is to finally have GPUs that impleme
; R0 O" E7 I1 @, z. ~4 t. z6 T0 fnt a protected audio path capable of handling these overly encrypted audio str
: J0 {0 O q1 K8 Z x9 U. W- k& n# [eams. Within a year everything from high end GPUs to chipsets with integrated ; `7 s* V/ T% s6 W
graphics will have this functionality. |
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发表于 2009-9-22 14:33
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