The GIMP-GAP FFMPEG encoder can do (nearly) lossles MPEG cut.
This should give same quality as the original
when your input videos are already compressed MPEG videos.
(such as DVD's)


The lossless MPEG-cut is still an experimental feature,
and may sometimes produce output videos that do not
playback properly on all players.


To use lossless MPEG-cut GIMP-GAP must be configured
with:

--enable-videoapi-support
--enable-libavformat 
--enable-libmpeg3

the required libraries must also be installed on your system.



Create a STORYBOARD file, with an editor or with the
Storyboard dialog, containing the desired clips of your videofiles.

Lossless encoding becomes possible if the STORYBOARD file uses only
one videotrack and the input clip(s) are MPEG ecoded videos
in the same size as defined in the VID_MASTER_SIZE record
Further there should be no transformations
(such as ZOOM, MOVE operations) and no MACRO executions
on the clips that are to encode.

Another requirement is that you set libmpeg3 as your
preferred video decoder:


-------------------------- begin STORYBOARD example -----------------
STORYBOARDFILE
VID_PREFERRED_DECODER  libmpeg3
VID_MASTER_SIZE        width:720 height:576
VID_MASTER_FRAMERATE   frames_per_sec:25

VID_PLAY_MOVIE      track:1 file:"/dos/data2/shrek/vob_files/vts_01_0.ifo" from:000030 to:000050 mode:normal nloops:1 seltrack:1 exactseek:1 deinterlace:0.0 stepsize:1


-------------------------- end STORYBOARD example -----------------


Then call the Master Encoder to encode your STORYBOARD file 
(Menu: Video->Encode->Master Encoder)

You must select the FFMPEG Encoder
and set its Parameters like this:

  Select an MPEG video codec that matches your input video(s)
    "mpeg2video"     if your input clip(s) are .vob or .ifo file from DVD
    "mpeg1video"     if your input clip(s) are MPEG1 strams from VCD
 
  Dont Recode Flag: ON (checked)
  Intra Only Flag:  ON (checked)


  
The Dont Recode Flag in the GIMP-GAP FFMPEG encoder
will try to copy frames 1:1 from input video clips
where possible, and does call the FFMPEG encoder engine
for all the other frames.

This way the user may cut videoclips at any desired frame,
without respecting intra frame picture group boundaries.

If there is a cut that does not start with an intra frame
the encoder engine will be used until the next intra frame
with matching size is read in sequence.
Starting from this intra frame
it can copy the already encoded frames 1:1 from the input
MPEG video to the output MPEG video as long as the desired
frames are fetched in ascending sequence with stepsize 1.

If the quality settings for the FFMEG encoder are different
from th quality of the input videoclip(s) this will be
visible especially at those points, where the encoder
switches from encoding engine to 1:1 copy mode.



