[FFmpeg-devel] [RFC] AVFilter Parser

Michael Niedermayer michaelni
Tue Mar 25 22:32:41 CET 2008

On Tue, Mar 25, 2008 at 09:41:14PM +0100, Vitor Sessak wrote:
> > 
> >> 2- Let the ';' be interpreted like vrmsss's '*'
> >> Advantages, Disadvantages: Same as (1)
> > 
> > I don't think the choice of a symbol is important, it is the syntactic  
> > mechanisms to combine streams which are important. I suppose we can  
> > take everybody agrees on the key elements for that (functional or  
> > sequential composition of filters --meaning outputs of the preceding  
> > filter feed into inputs of the following one-- parallel or non- 
> > sequential composition, rearrangement of streams via appropriate  
> > namings, and feedback or looping). I don't think we are yet reached  
> > the perfect way to express these, but we're close.
> Maybe having both my ';' and your '*'. My ; is the last symbol in 
> precedence, yours is the first. Mine operates in chains with no unlinked 
>   pads. Yours operates in chains with one or more.

I think using () to override precedence is more natural than having 2
identical operators but with different precedence.

Also maybe see eval.c which contains a expression parser with +-*/^()...
Not sure how usefull such a design would be for filters though ...

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Thouse who are best at talking, realize last or never when they are wrong.
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