On 7 Dec 2003, Florin Andrei wrote:
> On Sun, 2003-12-07 at 11:30, an unknown sender wrote:
> > It is actually questionable if variable GOP size helps much
Huh? Unknown didn't realize that starting a scene change with an
I frame is a good thing - and that's what variable gop sizes are
good for. Some editors, Final Cut comes to mind, allow you to
place 'compression markers' in the stream to set a point at which
a new GOP should start - used for sudden scene changes with encoders
that don't do the detection automatically (like mpeg2enc does).
A reasonable minimum size is 6 (that's what the microDV camcorders
used as their GOP size as it turns out - horrid format though for
editing, the picture quality's ok but that's about it)
> You mean, by default mpeg2enc creates fixed-size GOPs?
No! mpeg2enc creates variable length GOPs by default. If you want
closed ones use "-c". If you want fixed size GOPs then set -g and -G
to the same value ("-g 15 -G 15").
Cheers,
Steven Schultz
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