[MPlayer-users] Bugreport: "Smearing" on second pass of two-pass encodes

[Matthew Stephenson]

Hi, 

	Second bugreport of the week  - thanks to Michael Niedermayer for
solving my problems with rescaling.	I'm having some interesting issues with
mencoder's two-pass process. I'm encoding from a high-bitrate (8000kbps)
file taken from dvd source with mencoder single-pass. This file is
perfect. I'm then using two-pass encoding at 1536kbps to reduce the
filesize, and at the same time doing rescaling from 720x480 to 640x480
since the dvd aspect ratio is messed up. 	The problem occurs with
the second pass, and manifests itself as nasty smearing and blocking of
certain parts of the video. The first pass encode at the same points is
fine. In addition, playing the second-pass file while encoding it, I
noticed that these artifacts (which occur in the first minute of the
encode) only appear as the encoder nears the middle/end of its run. 
I have created two 15-second clips (~5M each) from the first and second
passes, which illustrate my point (these were made using -ovc copy -oac
copy and the modified mencoder (modific-butt-ugly) mentioned earlier on
this list). Urls: http://away.net/~bobstay/pass1.avi and
http://away.net/~bobstay/pass2.avi
	Although these reports apply to version 0.6, I have also tried the
latest CVS, which gives me even worse results along the same lines.

I've omitted the output from mplayer on the two passes as it was
lengthy, but I can easily post it if you think it would be useful. The
command-lines used are as follows:

mencoder -o ccs3_pass1.avi -frames 45015 -divx4opts br=1536 -sws 2 -x
640 -y 480 -pass 1 ../ccs3_master.avi && mencoder -o ccs3.avi -frames
45015 -divx4opts br=1536 -sws 2 -x 640 -y 480 -pass 2 ../ccs3_master.avi

System details as follows:

Linux Distribution: Linux from Scratch
Kernel Version: 2.4.16
libc version: 2.2.1
X version: 4.2.0
gcc version: 2.95.3
ld version: 2.11
binutils version: 2.11

CPU version: Intel Pentium III (Coppermine) 800MHz
Video card: 3dfx Voodoo 3 2000
Video driver type: X built-in driver
Sound card type & driver:  Creative SBLive! Value with OSS drivers of
kernel

MPLayer version: 0.60