[FFmpeg-devel] [PATCH] Add null video filter

[Stefano Sabatini]

On date Sunday 2009-10-18 22:34:39 +0200, Michael Niedermayer encoded:
> On Sun, Oct 18, 2009 at 12:25:41PM +0200, Stefano Sabatini wrote:
> > On date Thursday 2009-10-08 00:18:25 +0200, Michael Niedermayer encoded:
[...]
> > > probably ok if extensively tested (for example benchmarks that it does not
> > > cause slowdown which would be an indication of extra memcpy being done
> > > somewhere)
> > 
> > With ffplay I didn't noticed significant slowdowns even with an insane
> > number of null filters (256).
> >
> > But I noticed some slowdowns with ffmpeg, even with a relatively small
> > number of null filters:
> > 16:  utime=4.876s
> > 17:  utime=6.368s
> > 18:  utime=9.501s
> > 19:  utime=15.745s
> > 20:  utime=28.246s
> > 21:  utime=53.067s
> > 
> > With 32 null filters the process seems to hangs, a quick inspection
> > with gdb revealed that the processing hangs in avfilter_poll_frame(),
> > anyway since the problem is not related to the present filter I
> > committed.
> 
> please elaborate
> what did you test, if not what was be commited?

With ffplay:
ffplay in.avi -vfilters "null,null,null,...,null"

With ffmpeg:
ffmpeg -t 5 -i in.avi -vfilters "null,null,null,...,null" -y out.avi

Note that even changing the filter (e.g. using vflip) I got the same
behavior, so I concluded that the problem was not depending on the
null filter.

Interrupting in gdb the second command got the debugger in the middle
of some avfilter_poll_frame() call, (which is not used by ffplay).

I'll try to inspect the problem more thoroughly, but I won't have much
time in the next week, if someone wants to jump in and help I'll be
grateful.

Regards.
-- 
FFmpeg = Fundamentalist and Frenzy Merciless Philosophical Erroneous Geek