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

[Stefano Sabatini]

On date Thursday 2009-10-08 00:18:25 +0200, Michael Niedermayer encoded:
> On Thu, Oct 08, 2009 at 12:04:48AM +0200, Stefano Sabatini wrote:
> > On date Wednesday 2009-10-07 23:45:19 +0200, Michael Niedermayer encoded:
> > > On Wed, Oct 07, 2009 at 09:42:21PM +0200, Stefano Sabatini wrote:
> > > > Hi all,
> > > > 
> > > > in attachment a zen null video filter.
> > > > 
> > > > Pedagogically useful.
> > > 
> > > it looks like it would break direct rendering, not passing
> > > get_video_buffer() through but rather ending in a malloc()
> > 
> > That's true if we assume that this patch depends on the
> > get_video_buffer() change patch.
> > 
> > Patch updated accordingly.
> > 
> > Regards.
> > -- 
> > FFmpeg = Faboulous and Furious Mortal Peaceful Eccentric Game
> 
> >  doc/vfilters.texi        |    4 +++
> >  libavfilter/Makefile     |    1 
> >  libavfilter/allfilters.c |    1 
> >  libavfilter/vf_null.c    |   56 +++++++++++++++++++++++++++++++++++++++++++++++
> >  4 files changed, 62 insertions(+)
> > be718603bac4691e58b1a2ab660a3b1db00073fe  lavfi-add-vf-null.patch
> 
> 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.

Regards.
-- 
FFmpeg = Fostering & Faithless Maxi Powerful Everlasting Genius