[PLUG] Resolved: Noisy mp3s

C W elcaseti at gmail.com
Thu Nov 15 21:58:55 PST 2012


No problem, glad you were able to get it to work.

On Thu, Nov 15, 2012 at 7:26 PM, Richard C. Steffens <rsteff at comcast.net>wrote:

>
> > On Thu, 15 Nov 2012 12:03:31 -0800
> > "Richard C. Steffens" <rsteff at comcast.net> wrote:
> >
> > Anyway, does anyone have any ideas about why the sound on my Linux
> > machines show this noise while the sound on two Winders machines does
> > not? And more important, is there anything I can do about it, other
> > than listening on XP while typing on Ubuntu?
>
> > <...>
> On 11/15/2012 04:23 PM, Dale Snell wrote:
> > Hard to say what this might be.  The only thing I can think of off
> > the top of my head is that you've got clipping somewhere.  Try
> > loading one of the errant files into Audacity and check for
> > clipping.  If it's there, use Audacity reduce the audio amplitude;
> > that should clear up the problem.
>
> Bingo. I had to check the box, "Show Clipping" in the View menu, and it
> was obvious. Clipping was present every time one of the speakers spoke.
> I used the amplify effect to reduce the amplitude from 0.0 to -1.4 and
> the clipping disappeared. However, while quieter, the noise was still
> present in the saved mp3 file.
>
> On 11/15/2012 06:40 PM, King Beowulf wrote:
>
> > Rich, what linux audio player are you using?
>
> I'm using a program called a python program called Transcribe. I get the
> same noise when using Movie Player. I'm guessing it uses the same
> underlying sound library as Transcribe, which uses gstreamer.
> Interestingly, though, the noise is not present when I play the audio
> with Audacity.
>
> > You said you "clean up" the
> > mp3 in audacity so is the sound quality bad in audacity or just another
> > player?
>
> I gave a wrong impression. I did not use Audacity to "clean up" this
> particular mp3. I have used Audacity for that purpose in the past, but
> not this time. It didn't occur to me to try since the noise sounds like
> an effect I get sometimes when filtering with Audacity.
>
> > As Dale mentioned, clipping could be a reason. Also, if you
> > didn't set up the noise filter properly you can have introduced some
> > static that depends on the mp3 codec and player (Fraunhofer licensed vs.
> > LAME for example).
>
> LAME is what's installed here -- at least for exporting mp3s from Audacity.
>
> > Also, you may wish to convert to a lossless format
> > (wav or flac) before editing in audacity.  Also, consider mp3 bit rate,
> > CBR vs VBR....
>
> This proved very useful. I imported the mp3 into Audacity at the
> beginning of this exercise (responding to these e-mails). Since it was
> already there, I exported the file as flac -- after the amplitude
> reduction. Now it plays nice and quiet in Transcribe and Movie Player.
>
> Thanks to both of you for your helpful ideas.
>
> --
> Regards,
>
> Dick Steffens
>
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