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

[Michael Niedermayer]

On Fri, Mar 21, 2008 at 04:54:57PM +0000, vmrsss wrote:
> Hi Vitor,
> 
> On 19 Mar 2008, at 18:48, Vitor Sessak wrote:
> > In a way, this is a problem. Now, the parsing of the filters are
> > separated of the initialization (but that may change before hitting
> > SVN). But to parse something like
> >
> > split, nop*rotate, picInPic
> >
> > There is no way to see the difference between
> >
> > (in1) ---> split ---> rotate ------+
> >               |                   picinPic ----> out
> >               ------> nop    ------+
> >
> > and
> >
> > (in1) -----+   +------> rotate
> >            split
> > (in2) -----+   +------> nop ------>   picinPic ----> out
> >
> > without knowing beforehand how many inputs and outputs each filter  
> > has.
> 
> Unfortunately, I am not sure I can parse your second graph above, but  
> in general yes, absolutely, without knowing the number of inputs and  
> outputs of a filter (let's call it its type), you can't parse a  
> syntactic form correctly. 

> This is irrespective of the language you  
> pick, I'd expect. 

A language which explicitly or implicitly specifies the number of inputs and
outputs does not have this problem. That said iam not suggesting that such a
language is a good or bad choice. Just that it can be done.
If you take C as example its clear from the source how many arguments each
function gets even without knowing the declaration of the function.

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

The educated differ from the uneducated as much as the living from the
dead. -- Aristotle 
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