Bidski said:
Sorry if im posting in the wrong area here.
Im experiencing a problem that is boggling my mind on biblical proportions.
I have a Gigabyte GA-M56S-S3 motherboard with Realtek ALC888 Audio Codec
(Realtek HD Audio) onboard sound card.
I have 2 problems which may or may not ne related (most probably not
related).
Firstly, my Mic In port (both on the front and the rear) produce a distorted
and ever repeating noise whenever a signal is applied and i am unable to
source where this sound is coming from or where it originated from. This has
only recently shown up and nothing has changed in the system either software
or hardware wise.
Secondly, the "Line In" audio device listed in the Volume Control is lagging
a couple of seconds behind the actual audio stream.
Is anyone aware of what might be causing such problems or are aware of what
could be done to possibly fix these?
If i have described these badly or further information is needed, just let
me know
Thanks In Advance
Bidski
Various sound effects rely on delay. You can check the Realtek control
panel for any "virtual" environment buttons. Try to reduce the configuration
to have as few special effects as possible. Mute unused inputs, if they
haven't already been muted.
"Concert hall realism" can be added by a sound driver, by adding echo on
purpose to the signal output. For example, my old sound chip, had a 30
millisecond echo added, which caused music played through the speakers
to sound "muddy". Disabling all sound effects did not remove the special
effect, and I had to replace the sound device with a PCI sound card. It
doesn't have the same problem. The problem was at the driver level, and
wasn't a hardware problem. If the driver is badly coded by the manufacturer,
there is nothing an end-user can do about it.
In addition to echo being added on purpose, certain programs will add
their own echo suppression software (the exact opposite process). This
software appears to stay in place all the time, and has been known to
interfere with the normal operation of the sound subsystem. Examples of
applications that might add that kind of software, would be multiplayer
games with in-game audio communications, or another example would be telephony
applications, where the speaker and microphone are allowed to operate
in close proximity (speakerphone). If a telephony program you add,
allows speakerphone operation, then it may be adding its own
echo suppression software.
Echo suppression involves subtracting a copy of the microphone signal,
from the signal fed to the speakers. I don't really know anything
about it. There is more here on the topic.
http://en.wikipedia.org/wiki/Echo_cancellation
I would say your two symptoms are related, but I don't know if
I could spot the offending software if I was sitting in
front of your computer.
The kind of testing I've done in the past involved.
1) A copy of Audacity from
http://audacity.sourceforge.net/
2) I draw a test waveform in Audacity. For example, a step waveform
or an impulse waveform, with a trapezoidal shape (as audio signals
should be band limited, so they don't exceed the Nyquist limit).
_____ __
/ / \
___/ ___/ \_____
3) Using a second program, I record the sound output. I wasn't able to
make Audacity record from the microphone, at the same time as I was
playing the test waveform. So I needed two programs running.
4) Say I make a test waveform 16 seconds long, with a large impulse
every four seconds. By recording the speaker output via the line_in
or Microphone jack, I can examine the waveform, and see how the
result correlates to the input. Using that test, that is how I
determined my sound subsystem had a 30 millisecond echo added.
You might see something in the recorded result, that suggests what
kind of effect is involved. For example, if there is a mathematical
loop between input and output (with a fixed delay buffer), which
does not attenuate the signal being added, then noises in the system
can remain at a constant level or grow with time.
The hard part, will be associating a piece of software, with the
symptoms. And I can't really help you there, as I have a lot of
trouble understanding software stacks, shims, and drivers.
HTH,
Paul
