[ lame-Support Requests-3493406 ] About floating point VBR settings...

Support Requests item #3493406, was opened at 2012-02-24 12:37
Message generated for change (Comment added) made by eblanca76
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Category: None
Group: None
Status: Open
Priority: 5
Private: No
Submitted By: Elio Blanca (eblanca76)
Assigned to: Nobody/Anonymous (nobody)
Summary: About floating point VBR settings...

Initial Comment:
I see recent lame releases added support for floating point values for the vbr switch `-V', and the floating point part is used to fine tune the lowpass frequency.
About this feature, is some detail added into the lame tag? I mean, since a modification in the floating point part affects the lowpass freq (which is already stored into the lame tag) is there a particular way for checking if a floating point vbr value was used?


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>Comment By: Elio Blanca (eblanca76)
Date: 2013-01-19 04:41

Message:
Well, I just found into libmp3lame/psymodel.c how the frac part of the `-V'
option gets used by lame-3.99.5.
I'm having a look at statement 2128 and subsequent ones, trying to
understand the code. Now, I see why the sk[] array is made of 11 entries
and not 10 as one would expect (it is accessed one position more in
statement 2135), what I really can't get is: why the value `-9.5' @ pos 3 ?
I expected this array to be monotonic in ascending values, but it is not.
Further, in statement 2128 you declare two floats `sk_s' and `sk_l'. ( BTW,
what do their names stand for? do `s' and `l' stand for short and long
(granules)? ) Why do you set start values for them, knowing they will be
set a couple of statements below? And why two floats are used if they
always get set to the same values (statement 2132 and 2135)?

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