AVS Forum banner

Status
Not open for further replies.
1 - 10 of 10 Posts

·
Registered
Joined
·
244 Posts
Discussion Starter · #1 ·
Recently I built a new PC with an Asus P4b266 motherboard (which has onboard C-Media chip CMI8738 with 5.1 audio) and a Pentium 4 1.6A.


I have been to the settings that allow you to choose 2-Channel/4-Channel/6-Channel output (6 Channel is L/F/R/SL/SR/Sub). I understand all that, but I am wondering how say 4-Channel, or 6-Channel sound gets routed to this chip for output. If I am running PowerDVD 4.0 XP, will that decode the audio stream from a DVD and output to the appropriate channels? I am betting NO.


So do I need some kind of software decoder that allows me to use the 4 or 6 Channel output correctly? I am trying to decide on some new PC speakers right now, and if I don't need a Dolby Digital and/or DTS decoder then it makes the decision easier. Since the computer is in the bedroom it will be used for watching DVD's and recorded TV. My video card is the ATI AIW Radeon 7500, which has S/PDIF output. My motherboard also came with both input/output S/PDIF connectors, so presumably I can record a digital stream, or maybe just use it for sound input.


So, the questions are...

1. How can I use the C-Media multi channel output for real 4-6 channel audio?

2. What can I use the input/output S/PDIF connectors for exactly?

3. Can I pipe the S/PDIF output from the Radeon into the S/PDIF input on the motherboard, then will the (up to) 6-Channel audio be split correctly for output?

4. Do I need a software decoder to decode the digital audio output by the Radeon?

5. Do I even need to use the S/PDIF output from the Radeon? Can I just use the analog outputs, or the S/PDIF output from the motherboard?

6. ???


Maybe I am not asking all the best questions right now, and I may have more questions based on some of the answers. I appreciate any help or information that you can give.


Thanks


Mike
 

·
Registered
Joined
·
1,624 Posts
Mike,


I don't have C-Media, but I do have an ATI8500DV and had to suffer through some of these same types of issues, so maybe something I say here may help.


A. DD Decode of S/PDIF

It sounds like you are asking if its possible to decode the output from the ATI S/PDIF by inputing it into the C-Media. Most very likely the answer is no - as far as I know, the only thing that decodes DD based on S/PDIF-in is the Audigy with the latest drivers from Compaq (though I'd expect official drivers from Creative that can do this in the not-distant future). Also, the Audigy cannot decode DTS based on the S/PDIF-in ...


B. PowerDVD

"If I am running PowerDVD 4.0 XP, will that decode the audio stream from a DVD and output to the appropriate channels? I am betting NO."


You lose, pay up! :) If you are sending the DVD audio out your CMEDIA to a receiver via S/PIF, then you set POWERDVD to 'S/PDIF' and the receiver/decoder handles the output. If you are using C-Media analog connectors (e.g., to feed 'powered speakers'), then set your C-Media to the number of speakers you have (e.g., 4) and then in POWERDVD specify the number of your speakers (e.g, 4). PowerDVD will 'downmix' the 5.1 audio to match the number of speakers you have hooked up to the C-Media. For the example of 4 speakers, I'd guess that the center channel audio ends up being 'split' among the Front Left and Front Right speakers by the POWERDVD down-mix.


Basically, your software DVD player (e.g., PowerDVD) handles the decoding of audio from a DVD if you have powered speakers connected to the CMEDIA analog outputs (or if you are feeding a receiver via analog). Your receiver handles the decoding of audio from a DVD if you are 'passing-thru' the audio digitally to your receiver.


C. ATI AIW

I have an 8500DV (AIW) instead of a 7500 AIW, but I think my info here applies...


C1. ATI DVD

If you are using MMC7.6 version of their DVD player, your choices are to:


C1.1. decode the DD and downmix the result to 2-channel to your soundcard (internally)

C1.2. pass DD (but maybe not DTS) out digitally from the ATI S/PDIF-out to an external decoder

C1.3. pass DD/DTS out from the CMEDIA S/PDIF-out to an external decoder.


If you are using an earlier version of the MMC software, you only have the first two choices.


C2. ATI TV

The TV audio only comes out of the ATI line-out (analog). You most likely want hook this up to your CMEDIA analog 'line-in'.


Here's answers to your specific questions:


"1. How can I use the C-Media multi channel output for real 4-6 channel audio?"


Assuming the C-Media has 4 or 6 channel analog output, yes. Otherwise, it would be necessary to digitally pass-through to an external decoder such as in a receiver.


"2. What can I use the input/output S/PDIF connectors for exactly? "


S/PDIF output can be used to pass-through DD/DTS to a reciever.

S/PDIF output can usually be used to send 2 channel audio as pcm (e.g., software CD player, windows sounds)

S/PDIF input I think would be used, for example, by a music recording application such as Cakewalk's Sonar. But to decode DD based on S/PDIF-in connector requires something like Audigy with latest Compaq drivers


"3. Can I pipe the S/PDIF output from the Radeon into the S/PDIF input on the motherboard, then will the (up to) 6-Channel audio be split correctly for output?"


I doubt it very much. See earlier explanation.


"4. Do I need a software decoder to decode the digital audio output by the Radeon?"


See earlier explanation of the PowerDVD and ATI DVD decoding capabilities



"5. Do I even need to use the S/PDIF output from the Radeon? Can I just use the analog outputs, or the S/PDIF output from the motherboard?"


You'll need to use the ATI analog outputs for the TV audio.


ATI S/PDIF is not needed if you are using PowerDVD (set Powered DVD to either the number of speakers, or to S/PDIF if you want to feed a receiver/decoder via C-Media S/PDIF-out).


ATI S/PDIF is only needed if you are using the ATI DVD and wish to use a receiver/decoder (and you do not want to use the C-Media S/PDIF-out if using the MMC7.6 version of the ATI DVD player)
 

·
Registered
Joined
·
244 Posts
Discussion Starter · #3 ·
Thanks alot, that information helps a ton. I guess that I need to read more documentation on PowerDVD, since I am planning on primarily using that for watching DVD's. I didn't know that it could downmix, or separate and output multi-channel analog audio. The C-Media that I have can do 6-Channel output, when it's selected there are three two-channel analog jacks (like headphone jacks) it uses to pass the audio. When it is enalbed however, you lose any analog input. It bascially takes the standard jacks for input/output/mic and use them as L/R, SL/SR, C/Sub outputs. No big deal there, losing the input capability. But now that means I won't ~have~ to buy something like Yamaha TSS-1 system, or Creative Inspire 5700 system which includes a DD/DTS decoder and accepts a S/PDIF input. So, I can concentrate on just getting the speakers themselves.


Time to starts tinkering with PowerDVD more. Thanks.
 

·
Registered
Joined
·
1,969 Posts
I have the dragon soyo...


Whatever else you do with the card, get 5.1 speaker set-up. It just does not properly handle 4.1 speakers. You wind up having to use the audio mixer to change speaker properties for certain programs. Also, no matter what I do, for some programs, like the hipix audio, will assume that one of the speakers is the center speaker and thus the main sound is too low--hopefully without huge bass from subs.


Hopefully, s/pdif out doesn't have quite these problems.

I also have cheap speakers. So I'm not quite sure there is a point to posting, but I thought you should know it handles 4.1 funny in some respects


Darius
 

·
Registered
Joined
·
46 Posts
Just a quick comment, I have the asus P4B w/onboard audio, after weeks of frustration, I disabled the audio and threw a nightingale pro in...haven't had a problem since, easily worth the 40 bucks....
 

·
Banned
Joined
·
374 Posts
Yesterday I got a Chaintech mobo for a friend of mine that have the same 8738 C-Media chip , it is 6channel but with no s/pdif in/out , I don't know how the hell to make it output ALL the 6 analog channels , after hours of struggling with it I managed to make it output 4 channels .

Its port has only 3 jacks (Line Out/Line In/Mic) , I know that the Mic jack SHOULD output Center/Subwoofer channels , but I don't know how to do it !!!!!


MichaelG


Could you please tell me how? or could you send me the driver and software for this chip?


Thanks in advance..
 

·
Registered
Joined
·
1,969 Posts
Is it only the soyo that's got a breakout board for the sp/dif? I use the onboard connection for my headset and the breakout for the analog speaker connection. I do seem to remember that it isn't possible, even with breakout for that cmedia to handle more than 2.1. I might be wrong, but I'm pretty sure there is some stupid limitation.


Darius
 

·
Registered
Joined
·
244 Posts
Discussion Starter · #9 ·
My Asus mobo did come with an additional conenctor that has input/output S/PDIF connectors. It is screwed into the back of the PC similar to a PCI card and connected to the mobo, with a small connector ribbon, so at least I have it on my Asus board too.


I have not tested using any S/PDIF connectors yet, but they are there.


Minael, to get the true 6-Channel output you need software that will use the 6 channels. I have PowerDVD 4.0 XP which has this. To get the correct decoded 6-Channel output I had to ...

1. select 6-Channel output from the audio tab in PowerDVD configuration

2. select 6-Channel output from the advanced menu in C-Media audio mixer

3. select programs->settings->control panel->audio

this opens another Audio setup where you can select the audio output for the computer (if you have more than one option).

Here is also where you declare how many speakers are connected to the computer, I selected 5.1 from the drop-down list.


After that I was able to plug my speakers (only have 2 right now) into each of the analog audio jacks on the back and hear the audio for either, the front speakers (no voice! so it was working), the center/sub (voice! from my left speaker in this case), the rear speakers (mostly soft effects). The movie I tested with was Cruel Intensions which had a DD5.0 track, so no sub output, and little surround effects (just mostly some background music).


I did test it in 4-Channel mode as well and it seemed to work well too, the voice was output to the each of the front speakers.
 

·
Registered
Joined
·
1,969 Posts
I've done the powerdvd thing as well, and I do get sound out of all my speakers. It's just that newer movies require a discrete center channel--I never mess with audio options in DVD setup, so I never change it to simple dd 2.0 or stereo--Usually because I want my subwoofer involved. So I end up with very low volumes.


If anybody can help, please tell

Darius
 
1 - 10 of 10 Posts
Status
Not open for further replies.
Top