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Dolby/DTS over Optical interface.

Last response: in Components
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January 12, 2010 11:57:42 PM

Hello,

I have this configuration -
ASUS Maximus II formula with SupremeFX Audio card,
HIS ATI 4850,
LG Blu Ray writer (Exact model not available right now),
4GB Ballistix 800 DDR2,
Intel Q9650 quad core.

Video connected to Samsung HDTV via HDMI (through DVI to HDMI connector).
Audio connected via Optical to Denon 29xx receiver.

In this configuration WILL I EVER be able to get

(1) Dolby/DTS multichannel sound ??
(2) HD sound TrueHD/Master ???

I dont care what I have to do (LPCM mode or bitstreaming) as long as I get the multichannel sound. I play a DVD which has Dolby Digital soundtrack (verified by playing in a Sony DVD player and AVR shows 'Dolby Digital').

When I play the same DVD using Windows Media Player in the PC, the player decodes the audio correctly as it displays Dolby Digital in the screen bottom pane but my AVR shows only DVD Stereo.

What am I missing?

I see conflicting reports about SPDIF, some say it does only 2 channel stereo while others say it does Dolby/DTS too.

Please HELP !!!!!!!!!!!!!!!!!!!! too much invested here....

Reg,
buildnewbie


January 13, 2010 1:48:29 AM

You don't say what operating system you're using. I have Vista Home Premium (32-bit), and I, counterintuitively, have to set ControlPanel/Sound/Playback to "Speakers" rather than "Digital Output" to get digital output. A sound card should pass through DD or DTS over the SPDIF by default. Make sure you have a current driver for the card from Asus, and then run back through your settings for the driver and the OS, letting them have default all the way, and see if that lets DD work for the DVD.

Blu-ray sound won't fit through SPDIF--too much bandwidth. I looked at the Asus website, and that card of theirs that comes with the motherboard doesn't seem to be sold separately, and it doesn't have its own spec sheet on the site. (That sucks. If the marketing department wants to run the whole show, fine, but they should at least try to talk to the the people in the company who actually know what the product is.) The specs for the mobo say the card has "Blu-ray support", a purposely meaningless bit of information that I take to mean that the card will put the correct signal out its line outs when you play a Blu-ray disc in your computer.

I don't know enough about HDMI connections to say whether it would be possible to send Blu-ray through the HDMI to your receiver on its way to the TV and have it do the audio.
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January 13, 2010 7:19:18 PM

Thanks a Lot for your time.

Sorry about missing the OS. I am using XP (SP3).

1) So are you saying for HD sound it will put the correct signal on the SPDIF port but not the HD quality?

2) I know you said u dont know much about HDMI but was wondering if others can comment on this part.

I see a lot about Realtek HD sound engine on the ATI card. If I can find s/w to do the decoding of the HD sound track will I get HD sound in LPCM mode over the HDMI port to the AVR which can then send to the speakers? If so what should I see being displayed on the AVR?


Thanks,
buildnewbie.
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January 13, 2010 10:08:42 PM

A Blu-ray disc has more than one version of the sound on it--at least three, in fact. The spec makes DD, DTS, and stereo PCM mandatory. Better ones will have a better encoding in addition to those three, and a better encoding has a bandwidth too great to be passed through SPDIF, for physical reasons. These require HDMI. Your Blu-ray player will do different things with these signals depending on what it's designed to do and what you tell it to do. If it can't pass, say, Dolby TrueHD through the HDMI because the receiver can't decode it, it might fall back on the DD that every disc has and send that out the SPDIF. So, yes, it will in effect "put the correct signal on the SPDIF port but not the HD quality".

I read up on HDMI just now, and it looks to me like the HD audio comes out over the HDMI cable by default. I think your conception is right, and I'd expect the AVR to say what it is, like "Dolby TrueHD", for instance. Everything is a bitstream, after all.
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