Homebrew CMI 8738 drivers Options

[d0gbert]

Hi everyone!

I'm currently working on WDM drivers for soundcards based on the C-Media 8738/8768 chip. I plan to release the entire source code under a BSD-like license sometime in the future. I'm mainly interested in the S/PDIF connectivity because the DAC of the card sucks.

For testing, you need:
- a CMI 8738-MX/8768 based soundcard with S/PDIF (which are available for around 10-15 USD)
- Windows 2000/XP

Some of the features are:
- bitperfect S/PDIF output for 16bit 44.1/48/88.2/96kHz stereo signals through kernel streaming / dsound / waveout
- bitperfect AC3/DTS passthrough
- multi-channel output (that disables the S/PDIF output port unfortunately)
- recording support
- basic mixer support
- UART support (but disabled for now)

Apparently, the C-Media chip supports only 16 bit contrary to the claims in their specs. I haven't been able to get 24bit output even with the official drivers. But 96kHz output seems to work fine on the newer 8738 chips.

You can help me by posting your chip version and configuration, and testing whether 16bit/96kHz and 24bit/48kHz output through kernel streaming works (foobar2000, winamp have the necessary plugins). I'm specifically looking for people who have means to tell a 16bit S/PDIF stream from a 24bit stream.
When the driver loads, it prints the version of your chip to the kernel debugger. You need a running instance of DebugView (http://www.sysinternals.com/Utilities/DebugView.html) to catch the strings. In other words: open DebugView before updating the drivers.

Note that the drivers aren't signed, so you have to install them manually (Update Driver => Install from a list or specific location => Don't search. I will choose the driver to install => Continue anyway).
A 64-bit build has been successfully tested, and I'll probably release a build sometime soon.

Here are the download links for the latest version:

http://code.google.com/p/cmediadrivers

So long,

dogbert

This post has been edited by d0gbert: Mar 14 2008, 20:30

[Leto Atreides II]

My system is a Soltek QBic 3801 with a built-in CMI 8768.

Bit perfect worked great, able to automatically switch to the correct freq unlike the DIO drivers I tried.

My stereo showed 44.1, 48, 96khz all worked great. 88.2 I think also worked but my stereo didn't know what to display when it was playing it, the display got a bit confused.

24-bit also didn't seem to work for me. It would continue to come out 16 bit with directsound selected. With kernel-streaming used in FB2K 24-bit wouldn't do anything at all, nothing would come out.

The major problem for me is that it seems to have disabled all the headphone outputs.

This post has been edited by Leto Atreides II: Oct 17 2006, 03:46

[d0gbert]

The major problem for me is that it seems to have disabled all the headphone outputs.

Try this version: http://mitglied.tripod.de/atproc2/CMI-091-release.zip

[Leto Atreides II]

The major problem for me is that it seems to have disabled all the headphone outputs.

Try this version: http://mitglied.tripod.de/atproc2/CMI-091-release.zip

Works great!

Thanks!

It seems that the volume is now much louder than with the regular drivers, but it's not such a big deal. Just gotta remember to keep the volume slider down. Or it could be I'm just imagining it.

Sorry I can't seem to get the debugging information to get captured properly to give you any further information about my setup.

[d0gbert]

new release 0.92:
- built with the latest WDK (version 5728)
- first AMD64/EM64T release - this driver should work on your Windows XP x64 installation and on Vista x64. To install the driver on x64 version of Vista, you must disable the driver signature enforcement during boot-up with the F8 key
- stupid fix for a nasty bug which rendered large parts of the mixer useless

I'm keen to know whether the driver actually works on Vista. So if you have a card lying around and some time, please test and report .

This post has been edited by d0gbert: Oct 21 2006, 12:55

[René Eske Jensen]

I'm keen to know whether the driver actually works on Vista. So if you have a card lying around and some time, please test and report .

Hi there!

Thanks for spending time on a driver for the CMI chip, the native driver really sucks.

Anyway, I have tried the driver both in XP and Vista, and it works well. I had some problems during installation in Vista (BSOD), but I think it relates to uninstalling the old driver (if I just uninstall the old driver I get the same BSOD). Using safe mode I had no problems installing the driver.

The driver works fine but I cannot turn off the digital output. I don't need to, but when the option to do so is present, it should work.

I can't choose multichannel output. I don't need it either, but I can see in the release note that it should be possible, so at least I should be able to.

Is the selection of sample rate on the output automatic and dependent on the input signal? Contrary to the native driver, your driver doesn't have any option to change the sample rate.

Anyway, thanks for a nice driver. Now I am able to get digital out in Vista. Thanks a bunch!

BR,
René

HW config:
Soltek 75FRN2-L
Athlon XP2500+
Terratec 5.1 Fun
Radeon 9600

[d0gbert]

I had some problems during installation in Vista (BSOD), but I think it relates to uninstalling the old driver (if I just uninstall the old driver I get the same BSOD).

Yep, that's a bug in the old official cmedia driver - I had the same problem with version 0639 I think.

The driver works fine but I cannot turn off the digital output. I don't need to, but when the option to do so is present, it should work.

The analog part of the card is a nice extra, and the main aim of the driver is to provide a bitperfect spdif interface, but...

I can't choose multichannel output. I don't need it either, but I can see in the release note that it should be possible, so at least I should be able to.

... u can turn off the digital interface by selecting a multi channel configuration in your "sounds and audio devices" control panel applet (number of channels >=4).
The problem you will run into is that the driver "forgets" the channel configuration after each restart.

Is the selection of sample rate on the output automatic and dependent on the input signal?

Uhm, yes, the sample rate is selected by the kmixer, the way it's supposed to be in every WDM implementation. That means that if you start playing a 48kHz 16bit wave PCM stream and nothing else is pushing stuff through the kmixer, the driver sets the card to 48kHz 16bit. If you start playing another wave stream, let's say 96 kHz 16bit, the kmixer queries the driver whether the stream can be played simultaneously, which isn't possible due to obvious constraints (no support for hardware mixing), so the kmixer downsamples the stream to the format of the current stream, mixes them together and sends the resulting stream to the driver / card.
This is obviously a pretty bad design flaw, and Windows Vista has the ability to somewhere define a default sample rate and resolution. I might add a control application some time in the future though which would implement similiar functionality and some more stuff.

Just another thing - the mute function doesn't work, at least not for the main volume control.

Yeah, and the DAC volume doesn't work on 8768 devices etc etc. There are plenty of hardware revisions out there, and the specifications from C-Media have absolutely no information about the changes and capabilities of each of those revisions.