Re: Re[2]: [MP3 ENCODER] 3.86a, bug with -h ? [re-send]

[Frank Klemm]

::  > What about an option "adjust-level-for-psycho-model", which increases the
::  > level for the threshold computation, so low level music is coded with more
::  > bits. To my mind low level pieces of music with a turned up volume control
::  > are coded with too less bits. lame is coding for a full scale SPL of about
::  > 90 dB and that's too less if you are listening at >100 dB full scale SPL.
::  >
::  > Options like '-b128' don't solve this problem. For medium level music
::  there
::  > are still too less bits. Only the low level parts get enough bits, may be
::  > also too less.
               ^ oops, too much is right

::  
::  This seems to be an ATH problem. But isn't the ATH adjusted according to the
::  VBR scale?
::
That is VBR scale?

::  It's right that a switch to manually adjust the ATH would be good, as I also
::  think that some low level pieces of classic music are encoded with too few
::  bits.
::  A rough solution is to completely disable use of the ATH with --noath
::  
Average Bitrate (fictitious example)

Level                          SPL for FS
below FS         70 dB   80 dB   90 dB  100 dB  110 dB  120 dB
   0            180     185     180     175     165     150     
 -10            175     180     185     180     175     165
 -20            165     175     180     185     180     175
 -30            150     165     175     180     185     180
 -40            130     150     165     175     180     185
 -50            105     130     150     165     175     180
 -60             80     105     130     150     165     175
 -70             50      80     105     130     150     165
 -80             20      50      80     105     130     150
 -90              0      20      50      80     105     130

So if you calculate the bitrate for SPL/FS = 90 dB, you
have the following deficiencies:

Level                          SPL for FS
below FS         70 dB   80 dB   90 dB  100 dB  110 dB  120 dB
   0            -       5       -       -       -       -
 -10            -       -       -       -       -       -
 -20            -       -       -        5      -       -
 -30            -       -       -        5      10       5
 -40            -       -       -       10      15      20
 -50            -       -       -       15      25      30
 -60            -       -       -       20      35      45
 -70            -       -       -       25      45      60
 -80            -       -       -       25      50      70
 -90            -       -       -       30      55      80


So if you calculate the bitrate for SPL/FS = 90 dB and set B_min=100, you
have the following deficiencies:

Level                          SPL for FS
below FS         70 dB   80 dB   90 dB  100 dB  110 dB  120 dB
   0            -       5       -       -       -       -               
 -10            -       -       -       -       -       -               
 -20            -       -       -        5      -       -               
 -30            -       -       -        5      10      5               
 -40            -       -       -       10      15      20              
 -50            -       -       -       15      25      30              
 -60            -       -       -       20      35      45              
 -70            -       -       -       25      45      60              
 -80            -       -       -        5      30      50              
 -90            -       -       -       -        5      30              

Using a bitrate of 
  max (SPL/FS80, SPL/FS90, SPL/FS100, SPL/FS110) 
you can hear at any volume without audible noise.

-- 
Mit freundlichen Grüßen
Frank Klemm
 
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