MEncoder errors when copying mpeg2 file

[orev]

Hello,

I'm seeing a bunch of errors from mencoder when trying to create a copy of the file (just trying to trim it down). Here is the command line I'm using:

mencoder file.mpg -ovc copy -oac copy -of mpeg -endpos 00:01:00 -o test.mpg

and the output (truncated):

MEncoder 1.0rc2-4.2.1 (C) 2000-2007 MPlayer Team
CPU: Intel(R) Core(TM)2 Duo CPU     T7300  @ 2.00GHz (Family: 6, Model: 15, Stepping: 10)
CPUflags: Type: 6 MMX: 1 MMX2: 1 3DNow: 0 3DNow2: 0 SSE: 1 SSE2: 1
Compiled with runtime CPU detection.
success: format: 0  data: 0x0 - 0xe9b89292
MPEG-PS file format detected.
VIDEO:  MPEG2  480x480  (aspect 2)  29.970 fps  8700.0 kbps (1087.5 kbyte/s)
[V] filefmt:2  fourcc:0x10000002  size:480x480  fps:29.97  ftime:=0.0334
==========================================================================
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)
==========================================================================
PACKET SIZE: 2048 bytes, deltascr: 245760
videocodec: framecopy (480x480 24bpp fourcc=10000002)
audiocodec: framecopy (format=50 chans=2 rate=48000 bits=16 B/s=24000 sample-1)
Limiting audio preload to 0.4s.
Increasing audio density to 4.
Writing header...
INITV: 0.200, 0.167, fps: 29.970
Pos:   0.0s      1f ( 0%)  0.00fps Trem:   0min   0mb  A-V:0.000 [0:0]
Pos:   0.1s      2f ( 0%)  0.00fps Trem:   0min   0mb  A-V:0.003 [0:0]
Pos:   0.1s      3f ( 0%)  0.00fps Trem:   0min   0mb  A-V:0.007 [0:0]
(...)
BUFFER UNDEFLOW at stream 0, raising muxrate to 1980 kb/s, delta_scr: 223418
BUFFER UNDEFLOW at stream 1, raising muxrate to 2178 kb/s, delta_scr: 203107
BUFFER UNDEFLOW at stream 0, raising muxrate to 2395 kb/s, delta_scr: 184643
BUFFER UNDEFLOW at stream 0, raising muxrate to 2635 kb/s, delta_scr: 167857
BUFFER UNDEFLOW at stream 1, raising muxrate to 2898 kb/s, delta_scr: 152597
BUFFER UNDEFLOW at stream 0, raising muxrate to 3188 kb/s, delta_scr: 138725
ERROR: scr 1.544, dts 0.000, pts 1.433
ERROR: scr 1.668, dts 1.501, pts 1.601
BUFFER UNDEFLOW at stream 0, raising muxrate to 3507 kb/s, delta_scr: 126114
ERROR: scr 1.673, dts 0.000, pts 1.505
ERROR: scr 1.855, dts 0.000, pts 1.601
ERROR: scr 1.860, dts 1.601, pts 1.702
(...)
Writing index...

Overhead: 1.418% (653432 / 46075784)
Writing header...

Video stream: 5988.216 kbit/s  (748527 B/s)  size: 44931556 bytes  60.027 secs  1802 frames
Audio stream:  192.000 kbit/s  (24000 B/s)  size: 1440000 bytes  60.000 secs

The file is from a VHS->TiVo dub. Also note the strange frame size (480x480), though that's normal for tivo video. My question is, are those errors something I need to worry about, or are they OK?

Thanks.

[disturbed1]

Those errors are multiplexed errors. Common with TiVo files. You'll need to use -mpegopts

MPEG muxer (-mpegopts)
The MPEG muxer can generate 5 types of streams, each of which has reasonable default parameters that the user can override. Generally, when generating MPEG files, it is advisable to
disable MEncoder’s frame-skip code (see -noskip, -mc as well as the harddup and softskip video filters).

EXAMPLE:
format=mpeg2:tsaf:vbitrate=8000

format=<mpeg1 | mpeg2 | xvcd | xsvcd | dvd>
stream format (default: mpeg2)

size=<up to 65535>
Pack size in bytes, do not change unless you know exactly what you are doing (default: 2048).

muxrate=<int>
Nominal muxrate in kbit/s used in the pack headers (default: 1800 kb/s). Will be updated as necessary in the case of ’format=mpeg1’ or ’mpeg2’.

tsaf
Sets timestamps on all frames, if possible.

init_vpts=<100-700>
initial video pts, in milliseconds (default: 200)

init_apts=<100-700>
initial audio pts, in milliseconds (default: 200)

vdelay=<1-32760>
Initial video delay time, in milliseconds (default: 0), use it if you want to delay video with respect to audio.

drop
When used with init_adelay the muxer drops the part of audio that was anticipated.

vwidth, vheight=<1-4095>
Set the video width and height when video is MPEG-1/2.

vpswidth, vpsheight=<1-4095>
Set pan and scan video width and height when video is MPEG-2.

vaspect=<1 | 4/3 | 16/9 | 221/100>
Sets the display aspect ratio for MPEG-2 video. Do not use it on MPEG-1 or the resulting aspect ratio will be completely wrong.

vbitrate=<int>
Sets the video bitrate in kbit/s for MPEG-1/2 video.

vframerate=<24000/1001 | 24 | 25 | 30000/1001 | 30 | 50 | 60000/1001 | 60 >
Sets the framerate for MPEG-1/2 video. This option will be ignored if used with the telecine option.

telecine
Enables 3:2 pulldown soft telecine mode: The muxer will make the video stream look like it was encoded at 30000/1001 or 30 fps. It only works with MPEG-2 video when the output
framerate, converted with -ofps, is either 24000/1001 or 24 fps. Any other framerate is incompatible with this option.

film2pal
Enables FILM to PAL and NTSC to PAL soft telecine mode: The muxer will make the video stream look like it was encoded at 25 fps. It only works with MPEG-2 video when the output
framerate, converted with -ofps, is either 24000/1001 or 24 fps. Any other framerate is incompatible with this option.

The errors you displayed will most likely cause playback and sync problems. Buffer underflows are bad.

Of the above options, you'll need to tinker with format, vbitrate. tsaf, and muxrate.

Maybe

mencoder file.mpg -ovc copy -oac copy -of mpeg -mpegopts format=dvd:tsaf -endpos 00:01:00 -o test.mpg

Would be a good starting point.

[orev]

Thanks for the input. I have adjusted the options, and resolved the errors, but I cannot find any information about what the impact of those options are. I'm now using:

mencoder file.mpg -ovc copy -oac copy -of mpeg -endpos 00:01:00 -o test.mpg -mpegopts tsaf:vbitrate=5800:muxrate=7500 -noskip -mc 0

The bitrate comes from the bitrate that Tivo uses when recording in Best quality. I just kept bumping the muxrate higher until it didn't complain anymore, but what is the impact of doing that?