[PLUG] Resolved: Noisy mp3s
Richard C. Steffens
rsteff at comcast.net
Thu Nov 15 19:26:13 PST 2012
> 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
> You said you "clean up" the
> mp3 in audacity so is the sound quality bad in audacity or just another
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.
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