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Homebrew CMI 8738 drivers
Doujinshi
post Jul 8 2009, 19:31
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Thank You for suggesting using /? to set Loop Thru On/OF shortcuts smile.gif

Latest version seems to fix strange popups ive been getting smile.gif

Thank you for amazing work smile.gif

This post has been edited by Doujinshi: Jul 8 2009, 19:38
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Manzoku
post Jul 9 2009, 11:47
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QUOTE (Vchat20 @ Jul 8 2009, 11:21) *
The pin layout looks identical to yours with the 'key' up in that corner. Whether or not it matches up is another story. Really all I am after is at least one spdif input via coaxial especially if I can get a bit-perfect recording or live decode to the analog 5.1 outs (which, unless I am mistaken, ac3filter is now capable of doing to some effect from a live input?)

OK, looks like my information wasn't too relevant if you want SPDIF in. On the card in my picture pin 86 of the 8738 chip (SPDIF in) is connected to the middle pad on the bottom row of the 5x2 solder pads, but when I had a quick try last night I couldn't get it to work with a +/- 0.5V SPDIF input. I suspect either I'm making an elementary mistake somewhere or it needs TTL levels (0 / 5V) in the same way that SPDIF out from the chip is at TTL levels, so an interface circuit is required. I'll probably try that at some point just out of interest.
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Dogbert
post Jul 9 2009, 13:07
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years ago, I've stumbled across a russian website where some guy described how he managed to add an electrical spdif-in port to his 8738LX. I can't find the site now, but with the technical specifications from cmedia which contain some circuit diagrams, this should be easy.


--------------------
http://code.google.com/p/cmediadrivers
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Vchat20
post Jul 10 2009, 02:52
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Well I guess I'll just have to take a day and start poking around on that solder pad and see what sticks. smile.gif

As it is, the linked pinout on the supported devices page looks somewhat promising. pin 1 on this card looks like it should trace back through a capacitor to the 12V pci pin and the SPDIF1 and SPDIF2 pins on the pad look like they 'may' trace near the relevant pins in the 8738 chip. Not 100% though. Again, would probably have to take time out to poke around some. smile.gif
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Manzoku
post Jul 10 2009, 12:02
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One point to bear in mind - the chip on your card is the same as on my Sweex card, a C3DX, and the data sheet I've been using (here) has this layout for the 5x2 connector:


Certainly on my Sweex card the connections I've traced so far (SPDIF in & out, Ground, and 12v) all fit in with this layout. As far as I can tell there isn't an SPDIF2 on the C3DX version of the chip. Tracing the connections with a multimeter is fiddly but not too difficult. I use a photo of the chip to give me a reference point on the board especially for the SPDIF in pin 86, otherwise I go cross-eyed.

As I mentioned earlier it's likely that SPDIF in needs an interface circuit to bring the signal up from +/- 0.5 V to TTL levels (good page here). There are plenty of circuits published to do this & I've ordered the bits, so will let you know how it goes.

This post has been edited by Manzoku: Jul 10 2009, 12:20
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Doujinshi
post Jul 10 2009, 22:16
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It seems like when i switch Loop trough on/off when soemthings playing (like a movie) i get "More data is available" OK popup

IS this something wrong with my instal or is this intended?

Can you get rid of it?biggrin.gif

thanks smile.gif

PS>obviously one can say, dont switch when somethign playing, but im playign my xbox, i switch HDTV to PC, fire up a movie and notice theres no sound, so i switch sound to PC (loop of) and get the popup ;p
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Dogbert
post Jul 10 2009, 22:42
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QUOTE (Doujinshi @ Jul 10 2009, 22:16) *
IS this something wrong with my instal or is this intended?

directsound is blocked when ac3 passthrough is active, and this is a somewhat unintended consequence. I'll have a look at it.


--------------------
http://code.google.com/p/cmediadrivers
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hardwareaddict
post Jul 11 2009, 17:55
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Hi,

Very good work gets done on making a driver i see.
I tried to read a lot of the thread from the beginning, but i'm missing an important aspect.

Apologies for asking a layman question.

I've got very musical ears.

Is the idea that basically a monkey-audio or FLAC file (something 'lossless') can get decoded without
losing quality to the SPDIF out to the receiver?

Is there some quality loss from the soundcard?
Or is the idea that normally spoken one of the digital to analog conversors lose quality and that this
solution is not using such conversion at all?

If so that is of course MAGNIFICENT.

As that would be a magnificent achievement, also as a person capable of programming low level myself i know
how difficult it is to support open software.

Really very very impressive piece of work, to support something for free as i smell real good intentions here and
that is really worth mentionning!

As my receiver is pretty ok (NAD T761), i'm of course looking for a method without losing sound quality too much to the soundcard,
is this achieving it? (don't go complain about speakers please - yes my 2 JBL speakers need an upgrade, sorry to say so but the best quality
speakers i didn't hear in sound studio's when i visited there some years ago - i see 'em at funerals).

Oh you guessed it, i'm just interested in stereo sound for now.

My current soundcard is useless. It is an Audiotrak Maya 1010. One of the channels has been blown up (so when playing stereo sound,
only 1 speaker works well, the other produces garble), it is possible some organisation tried hack it and tried use one of the channels as
input channel (if you reverse a speaker it works as a microphone - as you know lately the internet has been flooded with hacking programs,
awful). The company pchut.nl where i had bought it didn't exchange it for a new one, "as nothing is wrong". Which is ballony of course.

Now a solution where i get rid of the soundcard nearly completely, by bypassing it and using SPDIF is of course ideal
This time machine NOT on the internet connected of course.

I do realize that bad receivers have big problems here when getting the 'pure sound', but this receiver does not.
But that pure sound that is not getting resampled in the soundblaster way, that's exactly what i'm looking for and currently i've got
no budget for a new soundcard, and my oldie audigy i had given away of course as it is resampling itself smile.gif

Next question is which platforms get supported (as i'll install the OS that it supports best)?

Next question as you probably know that as well: is todays soundblasters still resampling the sound?

Is there a list somewhere which 10 euro soundcards this driver works for that do have a sony philips digital out?

Thanks in advance for answerring any of my questions,
Vincent
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Dogbert
post Jul 13 2009, 19:07
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Vincent, all of your questions are more or less answered on the googlecode page.

Doujinshi, I've released a new version. This is going to be the last version for quite a while because I won't have access to a full-fledged PC for a few months or so.


--------------------
http://code.google.com/p/cmediadrivers
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hardwareaddict
post Jul 14 2009, 16:39
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Hi Dogbert,

Great work.

I bought a sweex 5.1 audio card and driver doesn't install very well at vista 32 bits ultimate edition.
Then i went to hardware devices and fixed it there. It recognized it then as CMEDIA driver.

Defender totally turned off and rebooted.

It played fine for 2 minutes then stops playing (using foobar 0.9.4.1) and nothing can get it again to work except a reboot.
Tried this several times. Each time after about roughly 2 minutes it stops playing (song is 3 minutes actually).

Mouse clicking on another song doesn't let foobar play. Seems it detects hardware issue then.
Tried playing it to the SPDIF out.

All software are fresh installs. Vista fresh installed, new foobar downloaded and installed. No other software has been installed
at the system and it isn't on the internet.

p.s. machine is a dual k7 S2466 mainboard case is open and airco in room is functioning.

Note windows mediaplayer keeps playing. Not a very simple to use player it is though.

This post has been edited by greynol: Jul 14 2009, 18:11
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Dogbert
post Jul 14 2009, 19:49
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vincent, this sounds like a hardware issue indeed. I know someone who had similar problems playing music at 44.1 kHz. It turned out that the oscillator quartz was faulty, and when he swapped it for a new one, things turned back to normal.

This post has been edited by Dogbert: Jul 14 2009, 19:50


--------------------
http://code.google.com/p/cmediadrivers
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ERNiE-C
post Jul 16 2009, 19:04
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just wanna say thanks, this driver works absolutely flawless for my Trust 514DX in Windows XP and Windows 7 RC1, even after hibernation, unlike my ATI HDMI Output from my 780G board biggrin.gif

I'm mainly using foobar2000 with WASAPI-Output.

This post has been edited by ERNiE-C: Jul 16 2009, 19:05
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Manzoku
post Jul 17 2009, 15:41
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QUOTE (Vchat20 @ Jul 10 2009, 01:52) *
Well I guess I'll just have to take a day and start poking around on that solder pad and see what sticks. smile.gif

As it is, the linked pinout on the supported devices page looks somewhat promising. pin 1 on this card looks like it should trace back through a capacitor to the 12V pci pin and the SPDIF1 and SPDIF2 pins on the pad look like they 'may' trace near the relevant pins in the 8738 chip. Not 100% though. Again, would probably have to take time out to poke around some. smile.gif

Vchat20 -

Have now confirmed that as well as digital out (as in my earlier post) digital in can be connected up on a Sweex SC012 via pin 86 of the 8738 chip. It's necessary to bring the +/- 0.5V SPDIF levels up to TTL (0/5V) using a 74HC04 inverter (I used the circuit from towards the bottom of this page). Assignments for the 5x2 connector are as shown in my picture a few posts back.

SPDIF recording with Cool Edit Pro worked, as did SPDIF pass-through.

The SC012 is a half-height card with a full height bracket. I'm in the process of making up an extra half-height bracket to take the small 74HC04 interface board together with coax-in and coax-out sockets. Link to some pictures will follow, time permitting.
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Manzoku
post Jul 20 2009, 18:18
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This is the SPDIF in/out connector for the Sweex SC012. The soundcard bracket was cut down to half height size for my mATX PC, so the additional circuitry and sockets are on a separate bracket. If the SC012 bracket hadn't been cut down, everything could probably have been fitted onto it. Details of the circuit etc. here
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Doujinshi
post Jul 22 2009, 22:32
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QUOTE (Dogbert @ Jul 13 2009, 12:07) *
Doujinshi, I've released a new version. This is going to be the last version for quite a while because I won't have access to a full-fledged PC for a few months or so.


Thank you for fast update smile.gif

Works great smile.gif

I hope you get some rest from us all bothering you with little things wink.gif
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sam987
post Jul 25 2009, 06:27
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C-Media came out with brand new official drivers in July.

Don't know if you realized or not, but C-Media also came out with brand new version of their 8738 spec sheet back in Feb 2009 --- AND continues to advertise the chip as 24 bit in and out. Brand new registers in the spec sheet for 24 bit spdit out, AC3 control registers, and Mute PCI channel to analog DAC (my mute button on my keyboard may finally work).

http://www.cmedia.com.tw/pdf/PCI/CMI8738_6...1_registers.pdf

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sam987
post Jul 27 2009, 03:03
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QUOTE (Manzoku @ Jul 17 2009, 09:41) *
Have now confirmed that as well as digital out (as in my earlier post) digital in can be connected up on a Sweex SC012 via pin 86 of the 8738 chip. It's necessary to bring the +/- 0.5V SPDIF levels up to TTL (0/5V) using a 74HC04 inverter (I used the circuit from towards the bottom of this page). Assignments for the 5x2 connector are as shown in my picture a few posts back.


Isn't spdif supposed to be 0.5V.

http://en.wikipedia.org/wiki/S/PDIF
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Manzoku
post Jul 27 2009, 21:45
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Well, the specification says 0.5V to 1V. In practice you find that an unconnected S/PDIF coax output (eg on a stand-alone DVD player or CD player) has a signal that swings 0.5V either side of 0V, so is 1V peak-to-peak (or +/- 0.5V).

When the player is connected up to equipment that terminates the output with 75 ohms the signal level drops to around 0.5V peak-to-peak (+/- 0.25V).
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sam987
post Jul 28 2009, 19:31
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QUOTE (Manzoku @ Jul 27 2009, 15:45) *
Well, the specification says 0.5V to 1V. In practice you find that an unconnected S/PDIF coax output (eg on a stand-alone DVD player or CD player) has a signal that swings 0.5V either side of 0V, so is 1V peak-to-peak (or +/- 0.5V).

When the player is connected up to equipment that terminates the output with 75 ohms the signal level drops to around 0.5V peak-to-peak (+/- 0.25V).


But if your stereo is expecting 0.5V, why are you stepping it up to 5V? Won't it kill your stereo?
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Manzoku
post Jul 29 2009, 12:19
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QUOTE (sam987 @ Jul 28 2009, 18:31) *
But if your stereo is expecting 0.5V, why are you stepping it up to 5V? Won't it kill your stereo?


We're talking about S/PDIF input to the Sweex soundcard, not a stereo. It's stepped up to 5V for the S/PDIF input on pin 86 of the 8738 chip on the Sweex soundcard, because that's what it is expecting.

It's the S/PDIF output from the 8738 chip on the sound card that goes to the stereo/AV receiver. That is at 5V, and has to be stepped down to the level the stereo/AV receiver expects.
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marscay
post Aug 3 2009, 21:18
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Dogbert - first of all thankyou for the work with these drivers, it's really top stuff.

Do you think there would be any problem using 2 8738/8768 cards in 1 machine with your drivers? Reason being i need 1 for 44.1 PCM passthrough for my DAC and another for DD/DTS bitstreams for my processor.

I know you can generally use 2 soundcards if they're different chipsets but i fancy a couple of the cheap Trust 5200's as they have a dedicated SPDIF connector unlike Creative cards for e.g. where i need to use a 3.5mm to RCA plug.

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Dogbert
post Aug 5 2009, 01:28
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QUOTE (marscay @ Aug 3 2009, 21:18) *
Do you think there would be any problem using 2 8738/8768 cards in 1 machine with your drivers?


That's an excellent question. From the specs, it should work just fine, but I tried this once without success - the second driver instance didn't load no matter what. I tested this configuration with just the official driver and with both my and the official driver simultaneously. Perhaps it was my system setup that was flawed (it was on a mainboard with a VIA chipset after all) or I did some other things wrong, but that's just speculation.


--------------------
http://code.google.com/p/cmediadrivers
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marscay
post Aug 5 2009, 15:17
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QUOTE (Dogbert @ Aug 5 2009, 01:28) *
QUOTE (marscay @ Aug 3 2009, 21:18) *
Do you think there would be any problem using 2 8738/8768 cards in 1 machine with your drivers?


That's an excellent question. From the specs, it should work just fine, but I tried this once without success - the second driver instance didn't load no matter what. I tested this configuration with just the official driver and with both my and the official driver simultaneously. Perhaps it was my system setup that was flawed (it was on a mainboard with a VIA chipset after all) or I did some other things wrong, but that's just speculation.


Yeh i think there's every chance it won't work laugh.gif I've used 2 cards with success in the past but they were difference chipsets and software.

Managed to swap boards in my HTPC to one which has onboard SPDIF so i'll get by now with just the one c-media card.
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ERNiE-C
post Aug 6 2009, 19:29
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I have swapped my DAC/IntegratedAmp for a Primare SPA-21 AV-Receiver, now it seems like there's a lag in the Receiver, the SPDIF signal starts to play a second later, which results in cropped track starts, like the SPDIF-circuitry in the AV-Receiver would be in sleep mode and wakes up a little late.
Is there anything I can do on the driver-side?
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Naveb
post Sep 23 2009, 14:45
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hello,

what cables would i need to connect my c-media sound card to this?

http://www.coemaudio.com.au/Sources/DACs/183/

and if i do connect it this way, am i limiting the potential of my DAC?

thanks
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