> From: "Renato C. Cerchiari" <[EMAIL PROTECTED]>
> Date: Fri, 26 Nov 1999 14:27:00 -0200
>
> What's happenning with VBR in Lame?
> Encoding a song with version 3.54 give me an average bitrate of 150 kbps.
> The same song with version 3.57 give me 124 kbps.
> Parameters are the same in both cases (lame -v -h -k).
> Am I doing something wrong?
>
In 3.57, I forgot to remove these comments in quantize.c:
/* quality setting */
/* Adjust allowed masking based on quality setting */
/* db_lower varies from -10 to +8 db */
masking_lower_db = -10 + 2*VBR_q;
/* adjust by -6(min)..0(max) depending on bitrate */
// fac=(FLOAT8)(this_bits-125)/(FLOAT8)(2500-125);
// fac = 6*(fac-1);
// masking_lower_db += fac;
This increases the required quality if the number of bits becomes
small. i.e. if LAME wants to try to use a 32kbs frame,
it needs more 'quality' (quantization noise < masking) than it would
for a 128kbs frame.
But it is good to remove this fix and run with -V5 if you want to test
changes to the psycho acoustics. In this mode, LAME will encode every
frame so that the quantization noise < masking. If the masking
formulas were perfect, the result would be perfect. (and the results
are far from perfect right now :-(
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