[MEncoder-users] -endpos ignored

[belcampo]

mencoder /spvfs/tv/5012_20100725231500.mpg -o test.avi -oac copy -ovc 
copy -ss 780 -endpos 785
MEncoder SVN-r31745-4.2.3 (C) 2000-2010 MPlayer Team
158 audio & 340 video codecs
success: format: 0  data: 0x0 - 0xd6be9868
TS file format detected.
VIDEO MPEG2(pid=518) AUDIO MPA(pid=92) SUB Teletext(pid=35)  PROGRAM N. 1
VIDEO:  MPEG2  704x576  (aspect 3)  25.000 fps  10000.0 kbps (1250.0 
kbyte/s)
[V] filefmt:29  fourcc:0x10000002  size:704x576  fps:25.000  ftime:=0.0400
==========================================================================
Opening audio decoder: [mp3lib] MPEG layer-2, layer-3
AUDIO: 48000 Hz, 2 ch, s16le, 192.0 kbit/12.50% (ratio: 24000->192000)
Selected audio codec: [mp3] afm: mp3lib (mp3lib MPEG layer-2, layer-3)
==========================================================================
videocodec: framecopy (704x576 24bpp fourcc=10000002)
audiocodec: framecopy (format=50 chans=2 rate=48000 bits=16 B/s=24000 
sample-1)
Writing header...
ODML: Aspect information not (yet?) available or unspecified, not 
writing vprp header.
Writing header...
ODML: Aspect information not (yet?) available or unspecified, not 
writing vprp header.
Pos:   0.9s     22f (27%)  0.00fps Trem:   0min   1mb  A-V:0.084 [0:192]

Skipping frame!
Pos:   1.2s     32f (27%)  0.00fps Trem:   0min   1mb  A-V:0.084 [3271:192]

Skipping frame!
Pos:   1.6s     42f (27%)  0.00fps Trem:   0min   2mb  A-V:0.084 [3263:192]

Skipping frame!
Pos:   2.0s     52f (27%)  0.00fps Trem:   0min   3mb  A-V:0.084 [3270:192]

Skipping frame!
Pos:   2.3s     62f (27%)  0.00fps Trem:   0min   3mb  A-V:0.083 [3185:192]

Skipping frame!
^CPos: 397.6s   9944f (33%) 590.46fps Trem:   0min 571mb  A-V:0.066 
[3870:192]
Writing index...
Writing header...
ODML: Aspect information not (yet?) available or unspecified, not 
writing vprp header.

Video stream: 3870.903 kbit/s  (483862 B/s)  size: 192364527 bytes 
397.560 secs  9944 frames

Audio stream:  192.000 kbit/s  (24000 B/s)  size: 9564000 bytes  398.500 
secs

Placing -ss and -endpos at start or end doesn't make any difference. 
What am I missing ?

Henk