Delayed audio input and Mic In problems

[Guest Bidski]

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

[Guest Paul]

Re: Delayed audio input and Mic In problems

 

Bidski wrote:

> 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