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Bugs item #3187397, was opened at 2011-02-20 11:23
Message generated for change (Settings changed) made by robert
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Category: Libraries
Group: Quality
>Status: Closed
Resolution: Fixed
Priority: 5
Private: No
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Robert Hegemann (robert)
Summary: Strange compression behavior

Initial Comment:
I'm using lame 3.98.4

I was trying to compress some synth work today in Audacity at constant 128 and it was producing strange warbling, popping, clicking noises.

Then I took the .wav file and tried using lame on the command line to turn it into an mp3

Using lame at the command line with all the defaults and also using lame with the -h option still produced the warbling, popping, clicking sounds.  However, when I used the -f option instead, all the audio artifacts went away, which is strange because that's supposed to be the lower quality setting.

Sample audio clips including the original .wav source file can be found in this thread:

http://ubuntuforums.org/showthread.php?p=10475757

Thank you.

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Comment By: JavaLinuxDev (javalinuxdev)
Date: 2011-02-22 21:56

Message:
I tried using the command line options you suggested, and they were
successful in eliminated the audio artifacts.  Then I downloaded, compiled,
and installed the latest CVS version on Ubuntu 10.04 and compressed the
file using the default settings, and the audio artifacts were still gone,
so the CVS version does indeed seem to fix this issue.

Thanks :).

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Comment By: Robert Hegemann (robert)
Date: 2011-02-22 19:01

Message:
There is a fix in current CVS for this problem. (3.99 alpha 13) 

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Comment By: Robert Hegemann (robert)
Date: 2011-02-22 09:40

Message:
Can you try "-V5 -b128 -B128 -F" ?
This will trigger to use the newer VBR psy-model and quantization code to
produce a constant bitrate stream of 128 kbps. (This is only a test, not
recommended generally)

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Comment By: JavaLinuxDev (javalinuxdev)
Date: 2011-02-20 12:12

Message:
After playing around on the command line more, I found that the lower the
number you use with the noise shaping and psycho acoustic quality setting,
the more warbling and audio artifacts there are.  As in, -q 0 or 1 or 2
produces audio artifacts, while -q 7 or 8 or 9 does not.

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