AVS Forums Archives - BIG mystery - No 5.1 S/PDIF passthrough on Realtek AC97

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BIG mystery - No 5.1 S/PDIF passthrough on Realtek AC97
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Posted by: David O

Hi

I'm having serious problems trying to play DVDs on my HTPC - I can only get 2 channel PCM sound to pass through the S/PDIF out to my receiver.

The HTPC has got a Realtek ALC650 AC97 on-board sound, WinXP SP2.

I've tried both WinDVD 4 Platinum and ZoomPlayer 4. In the latter, I've used the following codecs:
Intervideo, Power DVD, CinePlayer, AC3Filter.

When I right-click on ZoomPlayer and ask for the graph details, it tells me that:
1. Microsoft DVD Navigator is outputting 48MHz AC3 sound, 0 bits, 6 channels
2. AC3Filter (or alternatively Intervideo audio codec) is taking this and outputting 16 bit 2 channel sound.
3. Realtek is tking this and outputting 16 bit 6 channel sound

So oddly, it looks like the Realtek part id okay, and the problem lies with the audio decoder down sizing to 2 channels, or with the DVD Navigator
reading 0 bits (though in that case how come I get any sound at all?)

I've double nd triple checked my settings, and tried every conceivable combination of codec settings, but no joy - how hard is it to pass through S/PDIF anyway??? Both AC3filter aand Intervideo only have 1 setting.

For a long time I suspected the Realtek drivers, though as noted above they don't seem to be the problem. I have tried the latest Realtek drivers - They give me no sound from the S/PDIF at all, so I'm sticking with what I got with my HTPC.

I have also installed an old CMedia card I had lying around - same 2 channels over S/PDIF.

Help is welcome at this point!!!

Posted by: chriscic

David,
I have the same on-board sound. I'm also using Zoomplayer and AC3filter.

Are you sure you've got the AC3filter set to output via SPDIF? Start playing a vid in Zoomplayer, select filter properties, AC3filter and make sure you have SPDIF selected. Looks to me like the audio filter is not properly set within Zoomplayer for SPDIF.

Also, do you have the AC '97 Audio Configuration applet loaded? Make sure you have "output digital" selected on the SPDIF-out tab.

I had the same problem at first until I figured out how to make sure SPDIF was selected via filter properties. Hopefully that's your problem.

-Chris

Posted by: David O

Thanks Chris

No I have checked everything lots of times. S/PDIF is selected in both the Realtek SoundManager (digital ouput only) and in the various audio codecs I am using.

I should mention one important factor I left out:

I hear 2 channel PCM only when I select an analogue speaker configuration with AC3Filter (or Intervideo etc.) - if I select S/PDIF output from the codec, I hear nothing at all. Now I have no analogue connections - so the 2 channel PCM is being sent through the S/PDIF connection.

Go figure ...?!?!

Posted by: Morphx2

Download older realtek drivers and try them.

Posted by: LeonidasVouros

Just a thought: HAS SP2 to do anything with it????
I have the same chip ALC650 NO PROBLEMS RIGHT FROM THE START WITH EITHER DD5.1 OR DTS.....

Posted by: gattaca

I've got the same problem except trying to the the ACL650 to work for anything w/ my Receiver...

see this post.. sorry I found this thread later

http://www.avsforum.com/avs-vb/show...529#post4878529

I also downloaded the latest Realtek drivers and that did not help...

Thanks, Vincent

Posted by: 90c4

I can't remember what the trick was, but I think that I got 5.1 passthrough to work by selecting two channel stereo in the speaker menu and output digital only in the SPDIF menu within the Sound Effect Manager. Give that a whirl.

Posted by: nickpicker

The ACL650 does not support 5.1 output, only 2-channel stereo.

Posted by: hammerdwn

quote:
The ACL650 does not support 5.1 output, only 2-channel stereo.

Not true!

quote:
I got 5.1 passthrough to work by selecting two channel stereo in the speaker menu and output digital only in the SPDIF menu within the Sound Effect Manager

Any selections in the speaker config setup page only apply to analog.

David O- Question: Is SOUNDMAN.EXE running on your system after startup? This is the Realtek initialization program and needs to be running all the time. Do you have another device like DVD player/STB with SPDIF that you can test your receiver with? Start checking those A/V receiver settings too.

Hammer

Posted by: baileyler

I have the ALC650 on my Asus P4G8X, and am using Win XP Pro SP2. The SPDIF works perfectly when I use PowerDVD XP (DD and DTS, including EX), but I cannot get multichannel when I use NVDVD or Zoomplayer (with various filters).

I finally gave up trying to figure out what the problem is, and have stuck with PowerDVD XP. I might give TT a try.

Posted by: Johnster

I agree..I have RealTek on-board sound and I'm able to use the spdif passthrough..but only with PowerDVD. I tried it with the ATI DVD player (and another I'm forgetting now)..and it wouldn't work.

Don't forget to use the "AV Rack" properties for the RealTek to passthrough the spdif also.

I think the real problem is with your DVD software...try PowerDVD.

Posted by: gattaca

I think we are all just trying to get it to "bit perfect" passthru to the receiver via the optical SPDIF...otherwise I agree. I've spent a lot of time reading things associated to this issue and I have people saying it works FINE and others saying that it can't work. I am so confused.

I understand that the Intel 925 MB there is a good jump to 7.1 support w/ much higher performing codecs but the AC'97 specification should support six channels at 48 kHz/20-bit.

Vincent

Posted by: pasha

gattaca,

I had similat problem with ZP and AC3Filter, and WinDVD codec.
PowerDVD codec works fine with ZP

Posted by: David O

quote:

David O- Question: Is SOUNDMAN.EXE running on your system after startup? This is the Realtek initialization program and needs to be running all the time. Do you have another device like DVD player/STB with SPDIF that you can test your receiver with? Start checking those A/V receiver settings too.

Hammer [/B]

Hammer:

Yes SoundMan is running - set to 2-speker mode and with S/PDIF Output to digital only. And yes, the receiver works perfectly well with an external DVD player, I have swapped out all the cables etc. and checked them.

To the poster who suggested WinXP SP2 may be the problem, I hope you are wrong! However there is a thread in the Theatertek forums which suggests SP2 is the cause of non-passthrough on S/PDIF for a Realtek card.

I am still mystified as to why the various codecs apparently change the signal from 6 to 2 channels...

pasha:
I will download and try PowerDVD XP tonight.

PS... ZoomPlayer stopped working completely yesterday after I installed DScaler 5 and ffdshow (to try S/PDIF using their audio codecs). DScaler doesn't co-operate well with DVD Region Killer and threw up an error message about region protection (irony: the disc in the drive was a Region 4 disc just like my player). After that ZoomPlayer refused to connect any video codec to the Overlay Mixer, even after reboot and reinstall. Sigh!

Posted by: hammerdwn

XP Pro SP2 works fine for my onboard Realtek ALC650. Does your mobo support SPDIF in? Maybe try the other port? Mis-labled in/out? If you try ZP again, make sure you look at the "External" tab- set them all to SPDIF, and play around with audio render device in the dvd settings tab (default direct sound works best for me).

Hammer

Posted by: David O

I have confirmed again that this happens with both the onboard Realtek ACS650 and with the CMedia CMI8738.

Both play through S/PDIF in PCM stereo if I select 2 channel stereo output from the various audio decoders.

All the audio decoders downconvert from "0 bits 6 channels" received from the DVD Navigator to "16 bits 2 channels", sent to the sound cards.

System sounds play in PCM stereo through S/PDIF on both cards.

This makes less and less sense. How could both cards, or all the audio codecs, be wrong?

Posted by: hammerdwn

quote:
All the audio decoders downconvert from "0 bits 6 channels" received from the DVD Navigator to "16 bits 2 channels", sent to the sound cards.

System sounds play in PCM stereo through S/PDIF on both cards.

It is normal for system sounds to be in PCM stereo. Only when you actually play a DD or DTS encoded dvd will your receiver switch over.

Where are you getting this "0 bits 6 channels" to "16 bits 2 channels" information?

Hammer

Posted by: David O

quote:
Originally posted by hammerdwn
Where are you getting this "0 bits 6 channels" to "16 bits 2 channels" information?

From the ZoomPlayer "Graph Information dialog box (right click while DVD is playing, select Filters/Graph Information). The 0 bits 6 channels is ouput from the "Microsoft DVD Navigator" to the Codec., converted to 16 bits 2 channels and ouput to the Sound device.

Could someone who has 5.1 passthrough working with ZP please tell me what you get if you do this...? I feel it is simply a missing setting somewhere but both sound cards make it so easy to enable passthrough (1 setting in WinDVD or AC3Filter, plus one setting in either the CMedia Mixer or the Realtek Sound Manager - it's hardly rocket science).

Posted by: stevethewheel

DavidO,

Just to think outside the box a minute...have you checked that your amplifier is set to decode the digital stream correctly? Many amplifiers auto-sense the input (stereo/5.1/etc) but can be accidently set manually as well.

This happens occaisionally in my setup, usually by one of the family who thinks any source needs to be manually selected and is a real pain to troubleshoot until you get used to it after which it is probably the fastest thing to fix.

While you are doing the troubleshooting make sure you have 5.1 material in play. Many DVD's do not use 5.1 during the intro (prior to the menu) and so the amplifier is only seeing stereo anyway....therefore even on autosense you see something like 'coaxial stereo detected'....or in the case of your MS DVD Viewer only stereo activity will be seen.

And I do not think your realtek onboard sound system should be converting the signal to 6 channels. If you want SPDIF out then the decoding will happen in your receiver. Nothing else should be decoding in the path. So the connection between your HTPC and the receiver consists of one lonely SPDIF.

Posted by: nickpicker

The manual of my onboard AC650 says it won't do passthru 5.1 via SPDIF but only 2-channel PCM. Could be that the chipset itself supports it but obviously several mainboard manufacturers tried to save some cents on licensing by disabling that feature.

Posted by: hammerdwn

quote:
Could someone who has 5.1 passthrough working with ZP please tell me what you get if you do this...?

Ok, I checked it on mine and get the same "0 bits 6 channels" to "16 bits 2 channels" information. Like stevethewheel says, there is no decoding taking place. The spdif "passes" the track from the dvd, "through" to the receiver digitally where it gets decoded.

Hammer

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