CM8738 problem: bad rear speaker audio.

[pirata]

Hi everybody.

First of all my gear: ECS (Elitegroup) P6BAP-Me motherboard, with chipset VIA Apollo Pro133 and C-Media 8738 AC'97 audio chip integrated. That chip is a 4CH-only capable version (no 6CH). Audio jacks: Line Out (front speaker output), Line In (it works as rear speaker output), Mic in. Processor: PIII 800MHz, 384MB RAM, HD Seagate 60GB 7200+Seagate 20GB 5400. Winfast GeForce2 MX 32MB. Running under Win XP Pro.

For the sound chip, I have downloaded the latest drivers from CMedia's website, much newer than the ones in ECS's website. From CMedia I also downloaded a 4CH test utility, which revealed that 4CH works fine (there is a light sound level-dependent noise, but it was OK by me).

I downloaded Intervideo audio decoder ver2.6 from doom9.org, along with the filters needed to play ac3 fro AVI. If I use it in a Graphedit graph or in Zoom Player, the 4CH and 6CH options are grayed out. The decoder thinks I don't have a 4CH capable audio device. I have tried with several audio renderers (Wave Out, Defaul DirectShow, Cmedia audio device...), and I've got always the same results: the 4CH and 6CH options are grayed out. The properties dialog window of the aduio rendere has a Tag called nChannels equal to 2 (always). The problem seems to be in the Intervideo decoder, since the audio device is 4CH capable (as the test utility revealed).

Why is 4CH grayed out? There is a registry entry for Intervideo decoder, but I don't know how to tweak it in order to make 4CH available. I don't even know WHY its 4CH support is disabled!

I've also tried with PowerDVD 3. In the Configuration dialog window there's a Hardware Info tab. There it is stated that no 4CH capable audio device has been detected.

--------NOTE-------------
In that Hardware Info tab, it is also stated that no hardware aceleration has been detected. I know for sure that my graphic card has software acceleration for MPEG2 decoding. I have used it in the past with PowerDVD, so the only reason for this is that I upgraded to Detonator 41.03 (from www.guru3d.com). That driver is really good. Provides with PAL/NTSC resolutions, and the Control Panel applet works (it was not so with the 40.72 I got from NVidia). 41.03 is not available on NVidia's website, though! Only on Guru3d's. Strange... Any idea?
--------------------------


Well: when I play an avi file with PowerDVD, Zoom Player or BSPlayer the audio is not 4CH, and the noise is certainly audible (Default Directsound device used).


Any idea? Thanks.

[MaTTeR]

In regards to the Intervideo audio filter, I don't think you can force multi-channel output if the filter doesn't detect your card properly. This sounds like what's happening.

I would uninstall the Intervideo filter and try Valex's wonderful AC3 filter here. (http://xvalex.hotbox.ru/programs/ac3filter/ac3filter_eng.html)

Edit- If for some reason you don't have luck with Valex's filter then try the Moonlight OdioDekoda filters, less features but seem to work.

[Milkman Dan]

I have a later version of the Cmedia multichannel chip on my Soyo Dragon+. I have the same thing happen to me where the dvd player software doesn't detect my multichannel card. However, the configuration software in the Cmedia drivers seems to play 4 channel and 6 channel sound just fine.

Originally posted by pirata
Hi everybody.

First of all my gear: ECS (Elitegroup) P6BAP-Me motherboard, with chipset VIA Apollo Pro133 and C-Media 8738 AC'97 audio chip integrated. That chip is a 4CH-only capable version (no 6CH). Audio jacks: Line Out (front speaker output), Line In (it works as rear speaker output), Mic in. Processor: PIII 800MHz, 384MB RAM, HD Seagate 60GB 7200+Seagate 20GB 5400. Winfast GeForce2 MX 32MB. Running under Win XP Pro.

For the sound chip, I have downloaded the latest drivers from CMedia's website, much newer than the ones in ECS's website. From CMedia I also downloaded a 4CH test utility, which revealed that 4CH works fine (there is a light sound level-dependent noise, but it was OK by me).

I downloaded Intervideo audio decoder ver2.6 from doom9.org, along with the filters needed to play ac3 fro AVI. If I use it in a Graphedit graph or in Zoom Player, the 4CH and 6CH options are grayed out. The decoder thinks I don't have a 4CH capable audio device. I have tried with several audio renderers (Wave Out, Defaul DirectShow, Cmedia audio device...), and I've got always the same results: the 4CH and 6CH options are grayed out. The properties dialog window of the aduio rendere has a Tag called nChannels equal to 2 (always). The problem seems to be in the Intervideo decoder, since the audio device is 4CH capable (as the test utility revealed).

Why is 4CH grayed out? There is a registry entry for Intervideo decoder, but I don't know how to tweak it in order to make 4CH available. I don't even know WHY its 4CH support is disabled!

I've also tried with PowerDVD 3. In the Configuration dialog window there's a Hardware Info tab. There it is stated that no 4CH capable audio device has been detected.

--------NOTE-------------
In that Hardware Info tab, it is also stated that no hardware aceleration has been detected. I know for sure that my graphic card has software acceleration for MPEG2 decoding. I have used it in the past with PowerDVD, so the only reason for this is that I upgraded to Detonator 41.03 (from www.guru3d.com). That driver is really good. Provides with PAL/NTSC resolutions, and the Control Panel applet works (it was not so with the 40.72 I got from NVidia). 41.03 is not available on NVidia's website, though! Only on Guru3d's. Strange... Any idea?
--------------------------


Well: when I play an avi file with PowerDVD, Zoom Player or BSPlayer the audio is not 4CH, and the noise is certainly audible (Default Directsound device used).


Any idea? Thanks.

[pirata]

In regards to the Intervideo audio filter, I don't think you can force multi-channel output if the filter doesn't detect your card properly. This sounds like what's happening.

I would uninstall the Intervideo filter and try Valex's wonderful AC3 filter here.

Edit- If for some reason you don't have luck with Valex's filter then try the Moonlight OdioDekoda filters, less features but seem to work.

The Valex decoder is wonderful. THANK YOU! I get finally downmixing to 4 channels. The distorsion problem is still there. I explain myself: with Intervideo I got a sound in the rear output, but it was equal to the front sound, and charged with a noise that I recently understand it was distortion. As if some output amplifier was overloaded. Since my surround amp is broken, I am charging the rear output with a normal stereo amplifier and the front output with ... headphones. With that setup I did the tests and got the distortion problem.

I tried once with the amp connected to the rear output and nothing connected to the front output. The rear sound was much much more distorted. The connection of the headphones improved the sound inmediately and drastically, but distortion was still there. As I said before, the rear output jack, when used as Line In (output is 2 CH), works perfectly, so the problem is not the jack being broken.

I guess there have to be certain considerations to make when loading the output of a 4CH capable sound card. I do know that the load of a circuit can affect the output itself. That's the reason why you have to be careful with the speakers you attach to an amp. The circuit keeps its normal behaviour as long as the load stays inside of some boundaries. Maybe the amp and the headphones were unbalanced loads.

That led me to charge both outputs with the very same headphones (I happened to have 2 sets that were of the same model). The distortion was still there. Nothing changed. (notice that the front output is and has been distortion-free in all tests. It doesn't seem to be affected by the loads I use! Only the rear sound!)

I'd like to know if there are considerations to take into acount when attaching loads to such soundboards. I asked CMedia for information 2 weeks ago. I am still waiting for any answer coming from them...

Anybody out there? (thanks for reading this)

I have a later version of the Cmedia multichannel chip on my Soyo Dragon+. I have the same thing happen to me where the dvd player software doesn't detect my multichannel card. However, the configuration software in the Cmedia drivers seems to play 4 channel and 6 channel sound just fine.


Tell me about that "later version": SPDIF on it? 4 or 6 CH? Driver version? Downloaded form where? Do you use c:ºwindows\mixer.exe? What does it state in the About window? How did you assured that multichannel works?

Try PowerDVD XP. It doesn't detect the multichannel support, but if you enable 4CH, the Cyberlink audio decoder will downmix it well.
By the way: Power DVD detects my Nvidia acceleration. It was a problem with Netmeeting (!).

-----------P.S.
I begin to hate moherboard-integrated soundcards! I have another issue with recording sounds from Line In or Mic in! Even though when monitoring a sound input from mic or line in, the sound is noise free, when I record it to HD and then play the clip back, there is a quite loud and annoying white noise over the input!! I cannot record TV sound from my Hauppauge TVcard because the sound is too moisy. I have to use an old Soundblaster AWE 32 for that task!
The mainboard maker, Elitegroup, says I should change the BIOS... I don't think it will make a difference. They even tell me to clean the CHIP and the amplifier!!
Any idea about this one?

[Milkman Dan]

It says
CMI8738 chip
It has SPDIF out, is 6 channel
driver is 5.12.1.641
I got it from CMedia's site
I use the mixer app that came with the drivers.

Proved that the surround channels were functioning and discrete by creating my own 6 channel wav file, and playing it.

My onboard sound, overall, has been quite alright. Drive support has been good, and recording seems to work just fine, since my hardware MPEG-2 board doesn't output crap audio (it uses the line in).

[pirata]

Yep, my driver version is 5.12.1.642 not 939, as it is stated in the driver download page at CMedia's webpage.

PowerDVD will work with you 6CH too. Nevertheless, I really think you should give a try to ac3filter. It is impressive.

[bond]

I tried once with the amp connected to the rear output and nothing connected to the front output. The rear sound was much much more distorted. The connection of the headphones improved the sound inmediately and drastically, but distortion was still there. As I said before, the rear output jack, when used as Line In (output is 2 CH), works perfectly, so the problem is not the jack being broken.i know its a 3 years old thread, but i now also stumbled over this and i found the reason for the crappy sound:
the crappy sound happens only if you have nothing plugged into the front output, but into the rear output!
in that case, if nothing is plugged at the front, but speakers are plugged to the rear output, the card seems to try to play the front sound in the rear ones too, but it only manages to output it very distorted, with cracks aso
(these cracks also happen when you try to play a normal stereo stream)

as i say its only the front sound played in the rear speakers which has the cracks. the surround sound is played fine.
you can check this by playing one of these ac3 5.1 test samples, where a guy is saying "left front", "left surround" aso in the specific channel. if you play such a file you will see that the rear channels are played without cracks in the rear speakers, but you also hear the front channels in the rear speakers, but distorted

this gets fixed when you also plug in speakers in the front output. its also fixed if you only plug in a cable without speakers attached to it. also the stereo output via the rear speakers is fine with this

maybe this is helpful for someone :)