[MEncoder-users] Encoding with x264 Jittery Result

[Reuben Budiardja]

Hello,
I am trying to use mencoder to encode VOB files with x264 codec. I'm trying to 
get high quality encode with 1500 kbps target bitrate and two-pass encoding. 
The following is what I use:

mencoder CH_2.vob  -ovc x264 -x264encopts 
subq=4:bframes=3:b_pyramid:weight_b:pass=1:psnr:bitrate=1500 -nosound -of 
rawvideo -o  test.264

mencoder CH_2.vob  -ovc x264 -x264encopts 
subq=6:partitions=all:8x8dct:me=umh:frameref=5:bframes=3:b_pyramid:weight_b:pass=2:psnr:bitrate=1500 
-nosound -of rawvideo -o test.264

The options were basically taken from the example in Mplayer documentation, 
with the fast, low quality setting for the first pass and high-quality for 
the second pass.

The result is a very jittery movie. I checked that after the first pass the 
result is still OK, but after the second pass it's very jittery. Is there 
something that I did that's obviously wrong ? Although I glanced through the 
manual, I admit I don't really understand all the options (it's kinda 
overwhelming). 
Is there any recipe to get high quality two-pass encoding with 1500kbps 
bitrate ? I eventually wants to mux the sound (AC3) and subtitle in mastroska 
container.

Thank you for any help.
RDB