[FFmpeg-devel] [PATCH] [2/??] [3/3] Filter graphs - Parser for a graph description

[Michael Niedermayer]

On Wed, Mar 19, 2008 at 07:48:04PM +0100, Vitor Sessak wrote:
> Hi Michael, Vmrsss
> 
> Michael Niedermayer wrote:
> > On Wed, Mar 19, 2008 at 03:01:41PM +0000, vmrsss wrote:
> >> Hi Michael,
> >>
> >> On 19 Mar 2008, at 14:00, Michael Niedermayer wrote:
> > [...]
> >>> [...]
> >>>> As for the extra operator, you are right. However, I claim that in
> >>>> order to allow reusable libraries of graphs in your syntax you will
> >>>> have to provide a renaming operator, eg:
> >>>>
> >>>>  	{tmp1/in} (in)overlay(out) {tmp2/out}  = (tmp1) overlay (tmp2)
> >>> You are inventing some syntax and then complain about it, there is  
> >>> nothing
> >>> in the code nor in any mails from vitor suggesting anything like  
> >>> above.
> >> Hmm, I might not have made myself clear: sure you haven't suggested  
> >> anything like the above, I am arguing (and made a specific example in  
> >> support) that you **have** to if you want to reuse filters.
> > 
> > Look, as there is nothing specified about "reuseable libraries" any
> > system/syntax could be used, this clearly would allow to use "your syntax"
> > as well thus this is a proper proof that it cannot be worse than "your
> > syntax".
> 
> One problem about libraries of filter chains is that ideally they should 
> be more flexible than just some graph hunk. Citing an example of what 
> I'd like to be possible:
> 
> AVFilter avfilter_vf_rotate =
> {
>      .name = "rotate";
>      .init = init;
> 
>      {some magic to make it a pseudofilter}
> }
> 
> static void init(char *args, AVFilter *ctx) {
>      int ang= atoi(args);
>      switch (ang) {
>      case 90:
>          ctx->actual_filter = "transpose,vflip";
>          break;
>      case 180:
>          ctx->actual_filter = "hflip,vflip";
>          break;
>      case 270:
>          ctx->actual_filter = "vflip,transpose";
>          break;
>      else
>          snprintf(ctx->actual_filter, "rotate_slow=%d", ang);
>          break;
>      }
> }
> 
> But for doing this it would have to be a real filter, not something that 
> pasted some code while parsing the chain.

no, implement 1 filter doing generic rotations/flip/transpose with special
cases for what can be done faster.
And then just replace "transpose" / "vflip" / "hflip" by the appropriate
generic filter string

no code duplication, simple and fast

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

I wish the Xiph folks would stop pretending they've got something they
do not.  Somehow I fear this will remain a wish. -- M?ns Rullg?rd
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