[FFmpeg-devel] [PATCH 4/4] Make the crop filter accept parametric expressions.

[Michael Niedermayer]

On Thu, Sep 09, 2010 at 12:06:16PM +0200, Stefano Sabatini wrote:
> On date Thursday 2010-09-09 01:11:42 +0200, Stefano Sabatini encoded:
> > On date Wednesday 2010-09-08 15:56:27 +0200, Michael Niedermayer encoded:
> > > On Thu, Jul 22, 2010 at 07:52:35PM +0200, Stefano Sabatini wrote:
> > [...]
> > > > diff --git a/libavfilter/vf_crop.c b/libavfilter/vf_crop.c
> > > > index 6a7ae70..df9b5a2 100644
> > > > --- a/libavfilter/vf_crop.c
> > > > +++ b/libavfilter/vf_crop.c
> > > > @@ -24,7 +24,31 @@
> > > >   */
> > > >  
> > > >  #include "avfilter.h"
> > > > +#include "libavutil/eval.h"
> > > >  #include "libavutil/pixdesc.h"
> > > > +#include "libavutil/avstring.h"
> > > > +
> > > > +static const char *var_names[] = {
> > > > +    "E",
> > > > +    "PHI",
> > > > +    "PI",
> > > > +    "x",
> > > > +    "y",
> > > > +    "w",      ///< width  of the input video
> > > > +    "h",      ///< height of the input video
> > > 
> > > t for timestamp in seconds
> > > f for frame number
> > 
> > This will be only possible for x and y, as w and h cannot (yet) be
> > dynamically changed.
> 
> Another idea would be to implement a separate cropeval filter in the

no


> same file partly sharing the crop code, and perform x/y evaluation and
> validity checks in start_frame() (this to avoid to slow down the crop
> filter, which currently does just one evaluation during the
> configuration stage).

mplayer has a filter that does a eval per pixel so i dont think one per
frame will kill you


> 
> In the same way we could also add a cropfile filter which takes the
> crop values to be applied from a file, that would be useful for a

allow eval to read from a file, more generic more flexible and more usefull

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Asymptotically faster algorithms should always be preferred if you have
asymptotical amounts of data
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