[MPlayer-users] Re: Mpeg2 encoding results

Nico nsabbi at libero.it
Wed Sep 3 00:17:43 CEST 2003


>can u upload (to ftp://mplayerhq.hu/MPlayer/incoming and tell us that u did) 
>short samples (orginal source, lavc encoded, xvid encoded & command line 
>options used for both encodings) which show these problems (gray blocks & 

First a premise: I don't consider this comparison a  competition between xvid and lavc 
(which would also be unfair, since xvid compresses more that lavc's mpeg2), but only
a chance to show what I consider imperfections in the current lavc's outcome, so please let's avoid

In incoming/comparison/ there are three files:

1cnt.mpg and 1p.avi are from the same clean dvb capture. 
The mpg was generated with
mencoder -nosound -ovc lavc -lavcopts vhq:vcodec=mpeg2video:vrc_maxrate=9000:vbitrate=1500:vpass=[12]
the file is the second of two passes

the avi with
mencoder -nosound -ovc xvid -xvidencopts bitrate=1000:pass=[12]:me_quality=6 -vf crop=<something>,scale=704:416
(mplayer reports 1400 kb/s, but it's really 1000)

At the beginning you can see a black splash screen with the TV logo, with the mpeg it tends to be purple, 
and shows the first block storm; soon after look at the rocks in the sea: same effect (much more visible);
rocks seem to move with the water (which shows green blocks); same effect looking at the air 
when the boat sails in the sea; then pay  attention at the black jacket of the grey-haired man going dowwn the 
hall staircase: still blocks.

The corresponding xvid obvioulsy isn't perfect, but hides these  defects more efficiently, resulting in a much
more tolerable image.

For the second sample there is only the mpeg: sc2.mpg (tonight I will generate the avi, and let you know).
It was made without filters (although surely it needed a good denoise) and with a bitrate of 2500 kb/s in 2 passes.
If you pay attention 
- at the backs of the jackets of the drivers standing in the yard of the building, 
- at the dark hall of the building when the man goes out of it, 
- and the night scene when the man goes out of the car 
you will see the same blockyness, and only in black uniform areas.
Obviously the increase in bitrate improves the image, but 2500 is a bit high.

As soon as I find the movie that shows best the mosquito effect I will upload it.

Excluding these issues lavc is perfect, and fast too; it's a pity that the blockyness shows so much.



More information about the MPlayer-users mailing list