[FFmpeg-user] understanding copy flag

[Andy Civil]

On 2011-05-16 9:05 AM, David Overcash wrote:
> Some codecs don't play nicely with copy...

How can that be, when the codec shouldn't even be involved?

> Also - why would you essentially
> run "cp original.avi output.avi" through FFMPEG?

I would have thought it's pretty obvious that he's trying to debug something, 
(for example, why his output file is so big) and he's trying to start from an 
obvious "base", ready to tweak things and see what breaks it - and he's upset 
because even his obvious base seems broken. Clearly copying is not his 
objective, but one step in a debugging path.

P.S. I'm just guessing, but perhaps the original file has frames missing (e.g. 
it's declared as 60fps but only 30fps are present) and the 'copy' function is 
obediently duplicating frames (and inserting them into the output) to tidy up 
the mess.

-- 
Andy