[Ffmpeg-cvslog] CVS: ffmpeg/libavcodec motion_est.c,1.115,1.116

Corey Hickey bugfood-ml
Wed Dec 28 21:35:09 CET 2005

Michael Niedermayer CVS wrote:
> Update of /cvsroot/ffmpeg/ffmpeg/libavcodec
> In directory mail:/var2/tmp/cvs-serv19133
> Modified Files:
> 	motion_est.c 
> Log Message:
> hmm did i mess the scaling of these up at some point?
> anyway, this change decreases bitrate and increase PSNR by ~1.00 on my test file, other files also benefit significantly

I tested this on The Matrix:

for i in 1:turbo 2 ; do
  time mencoder ~/dumpstream/matrix.vob -aid 128 -oac copy \
  -vf crop=718:356:0:60,scale=640:272 -sws 9 -ovc lavc -lavcopts \
last_pred=2:vqcomp=0.6:vmax_b_frames=2:qpel -ofps 24000/1001 \
  -o test.avi


(pass 1)
PSNR: Y:40.06, Cb:44.34, Cr:44.64, All:41.10
user    35m12.394s

(pass 2)
PSNR: Y:42.10, Cb:45.17, Cr:45.85, All:42.96
user    186m52.325s


(pass 1)
PSNR: Y:40.05, Cb:44.29, Cr:44.59, All:41.08

(pass 2)
PSNR: Y:42.04, Cb:45.15, Cr:45.84, All:42.91


I don't have the user times listed for "after" because for some reason
my CPU frequency scaling went screwy and stuck my CPU at a low
frequency. Nevertheless, I don't think the encoding speeds are
significantly different -- the user times for after the next commit were
 34m52.509s and 190m8.100s, respectively for each pass.

Unfortunately, I didn't see a large PSNR gain like I had hoped from the
log message. The PSNR actually dropped a bit. As for quality
differences, here's the breakdown from looking at several different scenes.
- mostly the same (low-motion scenes are all the same)
- several places that look slightly better
- a few places that look slightly worse
- a few places that look significantly better
- one place that looks significantly worse
- one frame that looks way worse (flickering lightning for a second)

Overall, I have the impression that quality is improved.


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