[mythtv] NuppelVideo format, keyframes, and the cutlist

[Geoffrey Hausheer]

On Wed, 18 Jun 2003 12:47:46 -0400, "Craig Longman craigl-at-begeek.com
|mythtv/1.0-Allow|" <sa9nhe32c40t at sneakemail.com> said:
> Ben Bucksch wrote:
> 
> > Isaac Richards wrote:
> >
> >> Well, if there's something in there that tells it not to play X 
> >> amount of frames (for video _and_ audio), then that's fine.
> >>
> > Just wondering: Wouldn't that mean that the player has to decode up to 
> > 30-something frames in an instant? 
> 
> i don't think it would have to decode it, it could see the 'skip' frame 
> which would either contain a frame to skip to or a timecode, then it 
> could just look quickly at the next N frames to find what it wanted.  it 
> doesn't need to actually decode the frame to get the timecode/frame#,
> iirc.

Actually it does have to decode it.  Remember that we are cutting on a
non-key frame.  so if the frame we want is key-1 (i.e. the 29th frame
after the key), I need to decode frames 1-29 in order to get a proper
picture.  with my original proposal, I dn't have this problem, because I
gaurantee that the first frame after the cut is a key (because I will
encode it as such).  however, this will behave exactly like the cutlist
does today.  there will be ! the same lag as when watching a movie which
has been cut.  It is a tradeoff, and I'm not firmly committed to any of
the proposed solutions (I like isaac's micro-cut best from a cleanliness
perspective, but as said, it does have it's downsides.  Perhaps another
other option would be to force an 'I' frame at the cut point (without
making it a key frame).  this would prevent the need to decode the frames
between the last key and the cut-frame, but I'm not exactly sure how to
sync the audio in that case.

.Geoff
-- 
  Geoffrey Hausheer
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