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