[MPlayer-users] mencoder/lameopts aq=<value> ?

Haas Wernfried amnenion at xover.htu.tuwien.ac.at
Tue Jul 9 13:01:02 CEST 2002

i think i might found out what this value is being used for:
if you lower the value (aq=0), encoding time rises, with high values (aq=9)
encoding time decreases. i guess, that this is the switch for the "-q" in
(from lame manpage):
       -q qual
              0 <= qual <= 9

              Bitrate is of course the main influence on quality.
              The  higher  the  bitrate,  the higher the quality.
              But for a  given  bitrate,  we  have  a  choice  of
              algorithms  to  determine the best scalefactors and
              huffman encoding (noise shaping).

q=2 is recommended and always enabled when using vbr. 

q=value in lame seems to refer to the bitrate in vbr which is -V in lame

a few examples to illustrate this (only audio was encoded in 3-pass style):
Pos: 485.3s  12131f (100%)  65fps Trem:   0min   7mb  A-V:-0.045 [0:128]
filesize: 8.2 megs
ordinary cbr encoding...

Pos: 485.2s  12131f (100%)  31fps Trem:   0min   9mb  A-V:-0.016 [0:157]
9.9 megs
vbr with highest quality results in higher bitrate/bigger file...
time: user    6m4.300s

Pos: 485.2s  12131f (100%)  29fps Trem:   0min   8mb  A-V:0.017 [0:136]
8.7 megs
no big surprise, filesize/bitrate are lower now, encoding was a bit faster.
time: user    5m57.660s

Pos: 485.2s  12131f (100%)  46fps Trem:   0min   8mb  A-V:-0.016 [0:137]
8.8 megs
time: user    3m27.720s
filesize/bitrate are almost the same, but encoding was much faster (and
the quality should be worse than in (3)

if aq(mencoder) is -q (lame) (which i am quite sure) and q(mencoder) is 
-V (lame) the whole thing gets a bit confusing with these different q's,
maybe it would be wise to name them as in lame. maybe not, as this just
messes up existing encoding scripts and people wonder, why the q-switch
does no longe affect bitrate. however i hope you can now take add the
description for the aq-switch to the manpage.


-> Wernfried Haas - w.haas at xover.mud.at / amnenion at xover.mud.at 
-> Homepage: http://xover.mud.at/~amnenion
-> Beutelland: http://bl.mud.at

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