Sound clips when I have PCM DAC turned on

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What soundcard to you have (make, model, chip)?
CMI-8738

What steps will reproduce the problem?
1. Having PCM DAC turned on

What version of the driver are you using? On what operating system? What
version of the operationg system are you using (32 or 64 bit)?
1.2.6. Windows XP 32bit SP2

What ports of the soundcard are affected by the bug (e.g. SPDIF, Mic-In)?
analogue out

I have figured out accidently a strange thing, I don't know whether it is
due to your CMI driver or the card itself is faulty, but I describe the
problem here, it is quite interesting

A few days ago I managed to get to an analouge oscilloscope, and I've
decided to play around with it 'testing' the my sound cards as signal
generators...

I've already tested my 8768 card it can generate pretty good square signal
compared to onboard realtek which can't...

but in my other machine the onboard audio seems to have some problems, so
i've decided to put my 8738 card, which was not used, into that machine...

after i've put that card in that machine I've turned on the scope and the
signal gen program and seen that the upper and lower part of the sine wave
is cut... then I started playing around with the settings in your control
panel applet, and when i've turned off the pcm dac, the problem
disappeared...--> i've seen on the scope that the volume had changed (I can
hear it on my headphones too), and that clipping thing has also disappeared

do you have any idea?

Original issue reported on code.google.com by gazsi...@freemail.hu on 21 Jul 2009 at 11:25

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It seems that after I've been playing with the settings, I don't know exactly 
that
I've been doing the problem disappeared, but only up to the next reboot, now i 
can
reproduce this problem again

Original comment by gazsi...@freemail.hu on 21 Jul 2009 at 11:37

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these two should be the same ~1Khz sine:

http://kepfeltoltes.hu/view/090721/090721_134537_www.kepfeltoltes.hu_.jpg

http://kepfeltoltes.hu/view/090721/090721_134624_www.kepfeltoltes.hu_.jpg

I don't know whether this is a hardware problem or some driver problem

Original comment by gazsi...@freemail.hu on 21 Jul 2009 at 11:52

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the card itself is i don't know what make,model, it is a very tiny card, your 
driver
says: Hardware rev. :37; maximum channels:2; cmi-8738

Original comment by gazsi...@freemail.hu on 21 Jul 2009 at 12:00

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Interesting findings!

Unfortunately though, I don't have access to a full PC at the moment and this 
won't
change for approximately two months at least, so I'm not able to reconstruct the
issue. If, however, you can narrow down the bug to a configuration that can be
avoided in the code, I'd be happy to release a patched version.

Original comment by dogb...@gmail.com on 21 Jul 2009 at 12:05

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Thanks for your answer, I've investigated further and though I don't remember 
what
I've done this morning to make the problem disappear, but maybe the same as 
I've just
done:

If the PCM dac is turned on, the volume is much greater than when PCMdac is 
off, as
you may have seen in my photos too
and when PCMdac is off i can pull all the corresponding volume sliders in 
windows
volume control up to their maximum, the sound is still not clipped

but when pcm dac is on the volume is much higher 'defaultly', and the strange 
things
begin here:

the clipping seems to be occuring only when the 3 volume sliders (master,wave? 
(i
have a Hungarian text above it, it's the slider next to mastervol) reach a level
TOGETHER that is high for the ?card?

but it seems that Wave, and DAC are for the same purpose, and master is a bit
independent from them because:

-i can set wave and dac high AND master can be anywhere the sound is clipped - 
even
on a lower volume too

-but if I set dac&wave to a lower state, I can pull master up and reach a quite 
much
higher total volume (seen on the scope) without clipping

do you have any idea where to search next? or to what to look more precisely?

Original comment by gazsi...@freemail.hu on 21 Jul 2009 at 4:51

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Dogber!

today I've tried to look at this problem further, and I think I've managed to 
get to it:

I've been trying to get the exact levels where the sound gets clipped and if I 
may
find a more exact cause for this problem, so I've tried to catch on the scope 
the
level where the waveform gets clipped and I've figured out that there is a 
maximum
output level for the card I can reach WITH PCMDAC OFF is 1.92Volts on the scope
but not more.

If PCMDAC is ON, the output level is higher by default, and it seems that the
1.92volts is a maximum for the card, and as the level if much higher by default 
with
this setting on, setting the sliders higher it would exceed this 1.92volts --> 
the
output gets clipped to fit in this maximum

But the interesting thing i've also written yesterday is that if the wave and 
dac
sliders reach a level together (they multiply each others volume or i don't 
know, but
they set the output together), no matter is where the master is set, even at 
around
0,4Volts output, the output wave is also clipped

At this point i've found that with spdif-out switched off, the clipping 
disappears no
matter whether the pcmdac is on or off...
And with spdif out off, the volume does not change when i switch pcmdac on or 
off, it
stays at the same level
But for this setting also applies that the maximum output does not exceed 
1.92Volts
so that really seems to be a limit for the card itself

Some data I've measured for the 3 controls(master,wave,dac) for the card, you 
might
find it useful if you didn't know it already:

the wave slider seems to be much more fine volume setting slider than the other
two(dac, master), it can increase and decrease the volume continously
master,dac sets the volume in steps which are getting more and more fine as the
volume is getting closer to its minimum (0.8V, 0,8V, 0,4V;0,3V...) Dac uses 
slightly
higher steps than master

And these steps don't seem to be where the small lines on the windows mixer

Original comment by gazsi...@freemail.hu on 22 Jul 2009 at 11:36

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i have to correct for the above: step levels for vol controls aren't 0.8,0.8 but
0.08V,0.08,0.04,0.03 and so on...

Original comment by gazsi...@freemail.hu on 22 Jul 2009 at 12:54

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is it a this serious problem? , can that be really true that this card really 
does
not support spdif, because a quick and dirty solution for this problem is to 
switch
off the spdif out, and the solution for issue 56 is not to have spdif input 
on... ?
What do you think?

another thing: When i've first installed your driver for this card a time ago 
I've
noticed this problem with sound quality that it should be better with your 
drivers
but it is not with every volume setting, and now I could see it on the 
oscilloscope
that something is really wrong with the card, not with my ears... :)

Original comment by gazsi...@freemail.hu on 26 Jul 2009 at 6:17

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try going into DTS settings and changing output from 32bit to 16bit pcm

Original comment by clint...@gmail.com on 8 Nov 2009 at 4:21

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What DTS settings do you mean? This issue is about analogue output of the card, 
when
I have the option PCMDAC turned on. Then occurs this issue, I'm not playing any 
DTS
nor DD file.
The scope screen photographed in the pictures above (those can't be reached the
server might be down), is showing Sine signal:) but the output is cut, so it 
might
look square sign but it's not:)

Or what do you mean?

Original comment by gazsi...@freemail.hu on 8 Nov 2009 at 10:37

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Oh whoops. I was having this issue in Media Player Classic when playing video 
files
with DTS sound. It had been happening for weeks. That was my fix. Maybe not
applicable to you... But it fixed it for me.

Original comment by clint...@gmail.com on 8 Nov 2009 at 5:31

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And what did you notice in the sound? How did you recognize that the sound was
clipping? Because me, I could only recognize that though the sound quality 
should be
better with dogber's driver with that sound card too (I have an other card 
too), but
sometimes I could hear that the sound was not as clear as it should be, so it 
seemed
that there is some noise in the sound...from somewhere...
and some time later I managed to get a scope for some time, and I was playing 
around
with it,playing different waveforms and that time I noticed this issue
So I could look for a solution, instead of just listening if the sound is being 
a bit
better or not...

Original comment by gazsi...@freemail.hu on 9 Nov 2009 at 2:45

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For me, it was PAINFUL popping noises in the front, center, and left speaker.
Typically during explosions or louder parts. I watched about 5 movies like this,
getting depressed that I had finally learned to use AC3Filter properly in Media
Player Classic so as to take advantage of the AC3Filter Mixer. In the end, I 
went
back to direct passthrough. 

Original comment by clint...@gmail.com on 9 Nov 2009 at 3:34

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Your problem maybe different from this then, because (now the server is 
reachable so
you can see the pics I've uploaded) in the pictures I've taken of the 
oscilloscope
screen are showing that, the upper and lower parts of the waveform is cut (that 
is
the so-called 'clipping'), it usually occures when an amplifier is fed with a 
signal
which exceeds its' power supply voltage, and it can output only up to it's 
supply
voltage level, and when this occures the rest of the signal is cut...
But in this case i could even cause clipping with low level output, when the 
pcmdac
is turned on (and I don't know what other settings are affected with this too, I
don't remember, they are in the above posts...)
there are or were here issues inconnection with popping sound, in the issues 
list

Original comment by gazsi...@freemail.hu on 10 Nov 2009 at 2:18