[MPlayer-DOCS] CVS: main/DOCS/man/en mplayer.1,1.1186,1.1187
bugfood-ml at fatooh.org
Wed Dec 28 20:34:49 CET 2005
Guillaume Poirier wrote:
>>CVS change done by Guillaume Poirier CVS
>>+Refine the two motion vectors used in bidirectional macroblocks,
>>+rather than re-using vectors from the forward and backward searches.
>>+This option has no effect without B-frames.
>>+Use a wider search (larger values are slower).
> While I'm thinking about it, is it desirable not to activate this
> feature by default?
I haven't tested it enough to say how much it helps yet. I tried running
some short clips, but they were so short that the bitrate varied so much
to make the PSNR nearly meaningless. The impact on speed is odd -- it
slows down both passes, but the first pass more so.
Here's the encoding command, with fairly simple lavcopts:
for i in 1:turbo 2 ; do
time mencoder ../serenity_m420p.mov -nosound -ovc lavc -lavcopts \
-o 0.avi ; done
Here are the user times obtained for each pass. Note that I use turbo
for pass 1, which makes the first pass faster at low values of bidir_refine.
Also, for what it's worth, these times are from a P4; I suppose it's
vaguely possible an Athlon won't have such odd results.
> I'm trying to find what could be saner defaults for lavc MPEG4, and this
> option, depending on its impact on speed and quality could be one of
> those (like mbd=2 and trellis) which are to be on by default.
Once I finish testing Michael's other changes then I'll clear up some
disk space and test bidir_refine with The Matrix.
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