[mythtv] NuppelVideo format, keyframes, and the cutlist

Geoffrey Hausheer ou401cru02 at sneakemail.com
Mon Jun 16 23:14:17 EDT 2003


I am looking into how to process the cutlist without reencoding the whole
file, and I've hit a snag.  The nuv format asuumes that key frames (sync
frames) are always every x video frames apart.  This is used for
fast-forward, rewind and length determination, but not for linear
playback as far as I can tell.  The problem is that after removing a
block of frames as specified in the cutlist, I am not gauranteed that
there are x frames between the sync-frames around the cut.  To me this
loooks like I need to rewrite all of the sync-frames in the file.  This
kinda sucks because key-frames are generally associated with I-frames,
and I don't know what will happen if I move the key-frames without
reencoding the I-frames.  The only other solutions I can think of are (a)
change the nuv format to allow for a flexible range between key-frames,
or (b) add a new 'bogus' V frame which will act to fill up video-frames
between the key frames without changing the timestamp (this would also
break the video-length by a few seconds), or (c) encode blank frames
between the key-frames (this could result in as much as ~2seconds of
black-screen every-time a cut is processed).  I don't like any of these
options, so I'm looking for advice on what other possibilities exist. 
Remember that the whole point of this exercise is to remove the frames
denoted in the cutlist without reencoding the audio/video for the entire
file.

Ideas?
.Geoff
-- 
  Geoffrey Hausheer
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