Bugs item #1863245, was opened at 2008-01-03 16:03
Message generated for change (Comment added) made by bouvigne
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Category: Frontends (lame/mp3x/...)
Group: None
Status: Open
Resolution: None
Priority: 2
Private: No
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Gabriel Bouvigne (bouvigne)
Summary: Lame.exe reduces volume
Initial Comment:
Hello,
I just discovered that lame.exe reduces the volume
of encoded mp3-files by about 0.45dB.
When using the scaling switch "--scale 1.000" the
volume is OK.
This problem seems to occure when lame.exe is used and not for applications that use lame_enc.dll. Application with problem is Razorlame.
Goldwave is fine, because the DLL is used.
To reproduce, just convert a WAV or MP3 file once
with and once without "--scale 1.000" to see the
different output. Or convert same file with lame.exe
directly form commandline and once with goldwave.
I verfied above problem for 3.96.1 and 3.97 in the
same way on two PCs with WinXP.
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>Comment By: Gabriel Bouvigne (bouvigne)
Date: 2008-01-06 14:28
Message:
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The scaling was introduced to reduce clipping on near-full-scale input, on
low bitrate. The lower the bitrate, the lower the quantization precision.
As Lame does not have any specific provision against this, scaling input
was found to be a good workaround, at this time.
(but this was several years ago, so it might not be needed as much now,
even if ideally we would have some specific behavior in quantization
against this)
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Comment By: A. Raditsch (raditsch)
Date: 2008-01-04 12:40
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So the default scale is not "1.000" but something like "0.95".
Probably the decission was to help prevent clipping by
setting 5% off. If yes, that should be noted in the longhelp.
I never would expect that:
"lame x.wav x.mp3"
will reduce volume by 5%.
I think setting the 5% off is OK for PRESETS, but when working
directly with options, then the default scale should
be "1" ... wouldn't everyone expect that ?
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Comment By: Robert Hegemann (robert)
Date: 2008-01-04 11:14
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For CBR and ABR encoding there is some scaling done by intention, at
target bitrates below 256 kbps only. I don't know why, but I think there
was some good reason for doing it. Why it isn't the case when using the
lame_enc.dll is something I will try to investigate.
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