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http://we.pcinlife.com/redirect.php?tid=1259597&goto=lastpost
0 |3 u N; d8 X' V! ^2 H2 @http://www.anandtech.com/video/showdoc.aspx?i=3643&p=10
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9 N3 o/ M6 S( AThe Race is Over: 8-channel LPCM, TrueHD & DTS-HD MA Bitstreaming
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% n; B+ U3 T- e5 l; M- U. I% vIt's now been over a year since I first explained the horrible state of Blu-ra
" y a1 t2 E# x; \5 }y audio on the PC. I'm not talking about music discs, but rather the audio com; j6 ~" n. u/ ~. R- \' E0 }; m" S
ponent of any Blu-ray movie. It boils down to this: without an expensive sound
' @1 h) e M, y6 h" V3 Z6 ?( V5 Mcard it's impossible to send compressed Dolby TrueHD or DTS-HD Master Audio s0 V* q+ @) T d W
treams from your HTPC to an AV receiver or pre-processor. Thankfully AMD, Inte1 i8 e' ^. X# C3 \; n
l and later NVIDIA gave us a stopgap solution that allowed HTPCs, when equippe; `! Q$ S# L1 M6 F) \
d with the right IGP/GPU, to decode those high-definition audio streams and se( O* u2 g0 J& X6 p, |: n
nd them uncompressed over HDMI. The feature is commonly known as 8-channel LPC
6 r( z# q" p3 H+ x9 A) TM support and without it all high end HTPC users would be forced into spending
5 e5 y9 J7 a: ranother $150 - $250 on a sound card like the Auzentech HomeTheater HD I just , D m% h ]% U9 {1 l2 }& `1 P
recently reviewed. . G- C2 q& ~. P9 B4 h
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For a while I'd heard that ATI was dropping 8-channel LPCM support from RV870
3 b. C% Q+ ~ k. _% i2 zbecause of cost issues. Thankfully, those rumors turned out to be completely u. _, L( L, _2 N& y6 u, X) {# Z
ntrue. Not only does the Radeon HD 5870 support 8-channel LPCM output over HDM6 r$ t3 J; K$ ~" r' P: ?
I like its predecessor, but it can now also bitstream Dolby TrueHD and DTS-HD ' ]6 ~$ n% e9 } b* M
MA. It is the first and only video card to be able to do this, but I expect ot1 x1 J% l6 n# j7 }
hers to follow over the next year. # n- w. L. V& s6 P6 I0 e# t
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The Radeon HD 5870 is first and foremost a card for gamers, so unless you're b0 `* T: m0 _6 M$ _
uilding a dual-purpose HTPC, this isn't the one you're going to want to use. I
& S/ ^4 q% s S' ^, ~8 ]f you can wait, the smaller derivatives of the RV870 core will also have bitst
( S) }, T- `) s( S5 Hreaming support for TrueHD/DTS-HD MA. If you can't and have a deep enough HTPC
+ E$ d0 u* J1 c* scase, the 5870 will work. 8 ?; g) F+ a7 o0 S& Q- p
6 F; M y) c- v: oIn addition to full bitstreaming support, the 5870 also features ATI's UVD2 (U
& b$ V7 }, c- s8 T8 wniversal Video Decoder). The engine allows for complete hardware offload of al6 J/ q* n3 M) t: \% N/ K8 D! [
l H.264, MPEG-2 and VC1 decoding. There haven't been many changes to the UVD2
. v# L4 {6 ^3 `- a0 S+ hengine; you can still run all of the color adjusting post-processing effects a* P; I& q7 a2 G3 k+ j
nd accelerate a maximum of two 1080p streams at the same time./ i1 s' [- D# \& ~6 n
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ATI claims that the GPU now supports Blu-ray playback/acceleration in Aero mod
1 }, P8 Q( s" Y) E! [e, but I found that in my testing the UI still defaulted to basic mode.
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+ q3 {. J2 Z. ^ qTo take advantage of the 5870's bitstreaming support I had to use a pre-releas
+ y$ }! ]) s1 N( ue version of Cyberlink's PowerDVD 9. The public version of the software should
3 B2 c, T5 o' ]be out in another week or so. To enable TrueHD/DTS-HD MA bitstreaming you hav0 x- ~7 x5 Z8 f$ H2 Z
e to select the "Non-decoded high-definition audio to external device" option $ l% q( h, c4 K
in the audio settings panel:
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. z" Q8 _) h# N* j; c8 UWith that selected the player won't attempt to decode any audio but rather pas
3 K8 F) p w6 o% T1 W4 ^s the encoded stream over HDMI to your receiver. In this case I had an Integra( f# `! y1 q2 s) B8 b; F3 Q) J
DTC-9.8 on the other end of the cable and my first test was Bolt, a DTS-HD MA
; k# @8 ^% B! ytitle. Much to my amazement, it worked on the first try:
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No HDPC errors, no strange player issues, nothing - it just worked. 2 d( ]% R! F9 p% L$ r+ ^
. G" A1 [& c6 a/ c- P& RNext up was Dolby TrueHD. I tried American History X first but the best I coul
$ H% X5 R! Z/ r0 P7 b/ m4 Qd 【请注意文明用词】 of it was Dolby Digital. I swapped in Transformers and found the sam
% r7 g* z3 e* ] o/ me. This ended up being an issue with the early PowerDVD 9 build, similar to is2 k6 P7 ~ v4 I& I6 M
sues with the version of the player needed for the Auzentech HomeTheater HD. S/ O1 w) W0 Z- b2 h! f: l3 N% p
witching audio output modes a couple of times seemed to fix the problem, I now
, Z! J: @4 `, R+ L$ qhad both DTS-HD MA and Dolby TrueHD bitstreaming from the Radeon HD 5870 to m
8 h- z/ Z) @0 u+ y6 K# ~y receiver.
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" P( S' g m I: X" UOne strange artifact during my testing was the 5870 apparently delivered 1080i# g1 D# Z" t% B+ g. n
output to my JVC RS2 projector. I'm not exactly sure what went wrong here as - S: j) S5 Z6 W B) _
1080p wasn't an issue on any other display I used. I ran out of time before I
5 U2 V% \9 h4 `$ B. o Z2 W! d8 Scould figure out the cause of the problem but I expect it's an early compatibi0 A/ o7 l1 n( ]
lity issue. 2 k3 Y! z1 [ o4 ]) l( v. y
9 f9 Y3 j( H# @2 c/ u4 R: m. q; oI can't begin to express how relieving it is to finally have GPUs that impleme
3 }6 R4 r& j- D' K$ J" nnt a protected audio path capable of handling these overly encrypted audio str1 K6 E# j8 n7 ~' U: |
eams. Within a year everything from high end GPUs to chipsets with integrated 2 d* C4 J* H4 g/ {0 D+ D1 S
graphics will have this functionality. |
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发表于 2009-9-22 14:33
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