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# }9 o1 t+ ] R- ~. }http://www.anandtech.com/video/showdoc.aspx?i=3643&p=10 Q0 c% }: P$ Y
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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, {( ?$ q7 a9 S. B
y audio on the PC. I'm not talking about music discs, but rather the audio com
8 _3 F9 A6 J# m% s5 Eponent of any Blu-ray movie. It boils down to this: without an expensive sound
0 ^3 s+ W/ Y8 w/ ?card it's impossible to send compressed Dolby TrueHD or DTS-HD Master Audio s
' G# u: J- \! q z7 }! q2 |' }treams from your HTPC to an AV receiver or pre-processor. Thankfully AMD, Inte2 r' q6 C9 A5 t$ w8 c
l and later NVIDIA gave us a stopgap solution that allowed HTPCs, when equippe: Y& z+ l/ @4 E: N( x
d with the right IGP/GPU, to decode those high-definition audio streams and se: _& j$ J" l2 U1 f% B
nd them uncompressed over HDMI. The feature is commonly known as 8-channel LPC
) v. g# G* `' m% ?4 iM support and without it all high end HTPC users would be forced into spending5 ?/ p; q* |# c) `/ z% D# A
another $150 - $250 on a sound card like the Auzentech HomeTheater HD I just " {+ C6 `+ `$ i+ N
recently reviewed. . e. m; {3 c/ n6 j9 G6 |
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For a while I'd heard that ATI was dropping 8-channel LPCM support from RV870
+ I- x3 d0 U3 \8 ?because of cost issues. Thankfully, those rumors turned out to be completely u
2 K: E Y! q, W1 K" t1 E! tntrue. Not only does the Radeon HD 5870 support 8-channel LPCM output over HDM
# r6 m/ f3 w( c# m1 JI like its predecessor, but it can now also bitstream Dolby TrueHD and DTS-HD $ |* T9 n' ~, o3 X
MA. It is the first and only video card to be able to do this, but I expect ot
8 _( Q* e. D/ y: F3 ~ [hers to follow over the next year.
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The Radeon HD 5870 is first and foremost a card for gamers, so unless you're b% t7 y- {, G- h7 O; C! o
uilding a dual-purpose HTPC, this isn't the one you're going to want to use. I
' n! ` S; D" o8 t- h J3 mf you can wait, the smaller derivatives of the RV870 core will also have bitst
, |9 a/ J& J6 L5 n* M. \reaming support for TrueHD/DTS-HD MA. If you can't and have a deep enough HTPC
6 X S% c( P4 W6 ycase, the 5870 will work. ) E+ a" R) a% R' z @
" v* U( v# _2 z, n! XIn addition to full bitstreaming support, the 5870 also features ATI's UVD2 (U
! x+ L; d! V! vniversal Video Decoder). The engine allows for complete hardware offload of al; `8 A, u* B3 U' A1 ~" C
l H.264, MPEG-2 and VC1 decoding. There haven't been many changes to the UVD2
" `1 F3 D6 r+ j' Fengine; you can still run all of the color adjusting post-processing effects a6 M v+ {- n i7 y$ _8 x
nd accelerate a maximum of two 1080p streams at the same time.
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; p3 D+ G f4 |. L+ ]) z; T$ x4 yATI claims that the GPU now supports Blu-ray playback/acceleration in Aero mod' ~+ m* A q {! [* a! j/ i
e, 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
9 L' E/ ~3 m% b# ce version of Cyberlink's PowerDVD 9. The public version of the software should
* W, p6 t- @4 E# Gbe out in another week or so. To enable TrueHD/DTS-HD MA bitstreaming you hav, z5 I$ n& _' x2 g+ P
e to select the "Non-decoded high-definition audio to external device" option
% w2 {$ p8 ]+ M8 J( Nin the audio settings panel:
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- c" x! o% \/ JWith that selected the player won't attempt to decode any audio but rather pas
, y6 X4 L0 h' O3 }0 e8 Ws the encoded stream over HDMI to your receiver. In this case I had an Integra1 |. l( X& P! E, ~! V
DTC-9.8 on the other end of the cable and my first test was Bolt, a DTS-HD MA9 Z0 Z9 t0 c! ]
title. Much to my amazement, it worked on the first try:
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4 X: F9 x4 g& h' F$ ZNo 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
8 i. Z, G: E) K0 {* ud 【请注意文明用词】 of it was Dolby Digital. I swapped in Transformers and found the sam
: Y, E- c# Z9 ^e. This ended up being an issue with the early PowerDVD 9 build, similar to is
6 o1 e5 Z( t& Y& D* I; P! n6 X- v+ ^sues with the version of the player needed for the Auzentech HomeTheater HD. S
( o! a% I8 ?9 A: ~witching audio output modes a couple of times seemed to fix the problem, I now
0 `) f3 w6 j, W6 A5 d5 M' bhad both DTS-HD MA and Dolby TrueHD bitstreaming from the Radeon HD 5870 to m
7 K; h. r8 s3 `. s* u( t2 q) Sy receiver.2 y, G1 e7 T% B1 c8 _
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One strange artifact during my testing was the 5870 apparently delivered 1080i
, ~$ k4 Q& N6 i) D6 coutput to my JVC RS2 projector. I'm not exactly sure what went wrong here as & [6 o6 C9 @/ b. z4 t9 K/ N
1080p wasn't an issue on any other display I used. I ran out of time before I
6 b) O/ I) |) K' w' @7 A6 Mcould figure out the cause of the problem but I expect it's an early compatibi3 b# L/ i; H! I) _
lity issue. 9 Q1 w1 y5 G! Q% f
# ~" D9 e- U8 w8 T9 `9 [I can't begin to express how relieving it is to finally have GPUs that impleme
9 I4 l8 h0 a& k1 I4 A5 n) d8 ]7 Ant a protected audio path capable of handling these overly encrypted audio str' y3 w: k! ^1 a: ]* ]5 q
eams. Within a year everything from high end GPUs to chipsets with integrated
6 {* ]2 @- L) i$ T! pgraphics will have this functionality. |
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发表于 2009-9-22 14:33
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