[vlc] [Videolan-devel] strange parasites in frequency sweeping (was on videolan-devel)

[Rafaël Carré]

On Fri, 2008-03-21 at 13:00 +0100, Elie Roux wrote:
> Rafaël Carré a écrit :
> > On Thu, 2008-03-20 at 22:48 +0100, Elie Roux wrote:
> >   
> >> Hello,
> >>
> >> to test some headphones I wanted to hear the response of the headphones 
> >> according to the frequency. To do so, I took this frequency sweep :
> >>
> >> http://norgz.info/download/sweep.flac
> >>
> >> As you will hear, with VLC, there are very strange and annoying parasite 
> >> frequencies when it goes to high frequencies. This does not come from 
> >> the flac : you can try it with mplayer or by burning it on a CD, you 
> >> won't have those parasites. My version of vlc is the last debian/sid 
> >> version :
> >>     
> >> VLC media player 0.8.6e Janus (interface wxWidgets)
> >>     
> >
> > Try an unstable build from http://nightlies.videolan.org
> >   
> 
> Same result.

Might be related to your libflac version

> >> I have a few questions about these parasites :
> >>
> >> The main question is : Is it a bug or a feature ?
> >>     
> >
> > Does it reproduce at fixed timestamps ?
> 
> 
> It are parasites frequencies that appear only in high frequencies. They 
> appear between 6s and 13s...
> 
> >> If it is a feature I would be very interested in the precise reason of 
> >> these parasites, it looks like a sample problem, but I can't really 
> >> understand. I also think it would be interesting to have an option in 
> >> vlc to get the exact sound it is sensed to play, even if it takes more 
> >> processor ressources.
> >>
> >> A lot of other softwares do not pass the test of this sweep, for example 
> >> : gstreamer, mpg321... the only software that does it right is mplayer.
> >>     
> >
> > mplayer doesn't play the file, while gstreamer plays it well for me.
> 
> 
> It is sad that your mplayer (maybe you should bugreport ?) does not play 
> it, because it is the only player that works well for me... gstreamer 
> (like vlc) plays it, but adds parasites, we hear the sweep, and other 
> strange frequencies...

I think every player use the same libflac to decode it:
dpkg -l libflac8 says:
ii  libflac8       1.2.1-1ubuntu2 Free Lossless Audio Codec - runtime C
librar

You should try to install flac and convert your file to wav, to see if
it's still the same.

> >
> > Please use vlc at videolan.org in the future this is a more appropriate
> > mailing list.
> >
> > videolan-devel@ is reserved for ECP students afaik
> 
> Done.
> 
> By the way, http://www.videolan.org/support/lists.html does not work to
> subscribe to this list, I had to subscribe through
> http://mailman.videolan.org/listinfo/vlc

The page was not updated when we moved to mailman, I'll ask teh admins,
thanks.

> 
> Thank you in advance,
-- 
Rafaël Carré <funman at videolan.org>
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