[MPlayer-users] Re: How to suppress background noise

[Alain Barthélemy]

Le mercredi 29 octobre 2003, 09:16:06 ou environ Stefan Seyfried <seife at gmane0305.slipkontur.de> a écrit:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> Alain <cassandre at bartydeux.be> writes:
> 
> > I can hear the sound during capture (Volume-In on PC) and it sounds OK
> > but if I do:
> 
> this is direct loopback from line in -> mixer -> line out on the
> sound card. The hum probably is from a ground loop. Disconnect all
> antenna cables from the VCR, only leave the power and the a/v cable
> and the hum will be gone, i'm sure.
>  
> > mplayer test.avi
> > 
> > It is no more a hum I have but a distorted sound.
> > 
> > I don't understand because there is now a direct connection (via
> > amplifier) between Video-recorder and PC Line-In (not Microphone-In!).
> > 
> > With the same arrangement I can easily capture my Radio sound Output
> > and convert it to .mp3 without distortion. The only difference is the
> > Sound source (and combination with Video analog signal with mencoder).
> 
> What is your radio source? Probably it has a lover voltage than your
> VCR.
> Try adjusting the igain on your soundcard, this is, where the recording
> level is set, the "line1" slider is for the playback/loop-through-level.
> 
> I always use the "record"-tool (comes as part of the xawtv package on
> SuSE), it has a nice vu-meter in the console and "aumix" to set the mixer.
> 

Hi Stefan

Thank you for your answer. I tried aumix and I preferred it to Kmix or
Gamix. I have the same problem with aumix as with Kmix and gamix. When
I move the "line-in" slider the sound level goes up and down erraticly.
Difficult to understand what is happening.
As for the "record"-tool where do you find it on the Xawtv window or how
do you launch it on console? Happy to know there is a Vu-meter but how
do you launch it? I tried to type "record" but I have nothing. Is it
really delivered with the Xawtv package? What package?

> Also note that there are soundcards (crap like my soundblaster pci127),
> which cannot do full 16bit but start to distort heavily if the vu level
> is over ~50%. Fortunately record shows the signal level in numbers, so
> i just adjust igain so the vu never is > 15000.

Good to know.

> 
> Good luck.
> 
> Stefan

Thank you for all your proposition. Yesterday I start to view TV first
with KwinTV then with Xawtv. At first there was a very light hum then
the background noise (it was not background noise anymore) became
suddenly very loud. I wonder if it is not a problem of sound card. I
moved the sliders of aumix or the video and sound cables without effect. 
Problem thus is not solved. I hope to have a working Vu-meter to check
iGain.

-- 
Alain Barthélemy
cassandre at bartydeux.be
http://bartydeux.be
Linux User #315631