[MEncoder-users] x264 decoded too slow

Jeff Clagg snacky at ikaruga.co.uk
Wed Feb 1 08:52:20 CET 2006

On Wed, Feb 01, 2006 at 03:27:44AM +0100, Aleksandar Uzelac wrote:
>   this might be a topic for mplayer group, but i don't think the problem is up to the player (or codec). that is why i'm posting to this group.
>   most recently i compressed a dvd into a x264 video, here are options:
> "c:\Program Files\mplayer\mencoder" dvd://1 -dvd-device "h:\film" \
> -vf pp=fd,hqdn3d=2:1:2 -oac copy -ovc x264 -x264encopts \
> bitrate=1397:frameref=5:bframes=3:b_pyramid:weight_b:qp_min=1:\
> qp_max=51:qp_step=2:ratetol=2.0:4x4mv:8x8dct:me=4:me_range=24:\
> subq=6:psnr:pass=[133] -o h:\film.avi

qp_min=1 is not a good idea; even the default (qp_min=10) is quite
conservative. Probably doesn't matter much (if at all) in 2-pass,
but really qp=10 should be much more than sufficient to guarantee
perceptually transparent quality. And me=4 is just ridiculous, there is
no justification to use this for a normal encode. It makes more sense
to use me=3 with a larger me_range. That still won't improve much over
the default, but at least it won't be ridiculously slow. Finally, doing
three passes is almost never necessary for long encodes. It is, however,
useful for very short encodes  -- say, around 10 seconds or less.

> need not to say, because of me=4 and me_range=24 it took 15 days to
> finish this compression.

Proving my point that these options *never* belong in a normal encode.

> at the end, when avi is played with mplayer
> (or ffdshow, results are the same) it takes most of CPU resources it can
> (PIV 3.2GHz with HT, single thread can take up to 50% of total CPU power)
> in scenes with heavy movement (like when camera goes from one side to
> the other), and because of that (?) audio is not sync with video (sync
> is lost).

I have a 1.8ghz Athlon 64 ("3000+"), and for DVD resolution at this
bitrate, 35% cpu usage is typical. I suppose 4x4mv may have some
noticeable effect on decoding speed and it's the first option I'd
consider throwing out since it doesn't help quality in most cases.

Other than that, "use cvs," I find it to be 20% faster than pre7 with my
videos and someone using a 64-bit binary reported a 40% speedup.

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