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

[Michael Niedermayer]

On Wed, Mar 19, 2008 at 05:38:29PM +0100, Michael Niedermayer wrote:
> On Wed, Mar 19, 2008 at 03:42:39PM +0000, vmrsss wrote:
> [...]
> > (*) this should be clear from what I wrote previously, just in case  
> > I'll repeat it: the problem is that you cannot put together two  
> > previously defined graphs which happen to use a common name for their  
> > input pads, because you'll get confused as to which is which. You can  
> > of course modify one of the graphs by hands, don't think is  
> > particularly user friendly, then you'll have to provide a programmatic  
> > way to do so. It can be done of course, but it's not pretty, and it's  
> > not easy to explain to end users.
> 
> Ive provided a formal proof of equivalency already. You are trying to
> tell me that you dont understand math ? Because if you did you wouldnt
> argue against a proof ...
> 
> Non formally i could again point you to C and say that it doesnt matter what
> arguments to a function are named nor what local variable names are used
> in a function. You do NOT solve anything by ommiting names, its just that
> you then have no names. Which will negativly affect readability.
> 
> your system:
> 
> my_overlay= "picinpic*nop*nop,picinpic*nop,picinpic"
> 
> 
> a system with names:
> 
> (main, left, right, bot)my_overlay=
> "(main, left)picinpic,
>       (right)picinpic,
>         (bot)picinpic"
> 
> use of it is the same either way:
>  movie=  main.avi
> *movie=  left.avi
> *movie= right.avi
> *movie=bottom.avi , my_overlay
> 
> And yes a system without names is surely shorter, and so would be C if one
> ommited variable names and used rules to implicitly select them. This doesnt
> make it a good idea though.

and here is yet another alternative syntax:

my_overlay(main, left, right, bot){
    ret= picinpic(main, left)
    ret= picinpic(ret, right)
    picinpic(ret, bot)
}

my_overlay(movie:main.avi,
           movie:left.avi,
           movie:right.avi,
           movie:bottom.avi)



Thus we have the following syntax classes

1. Chain based

swap, !(nop*picInPic , swap , picInPic , denoise)
or
(tmp)picInPic , (in2)picInPic , denoise(tmp)


2. infix/prefix based

T= denoise ((in1 picInPic T) picInPic in2)


3. function based

T= denoise( picInPic( picInPic(in1,T), in2) )

This also nicely shows how "clear and readable" the nop*swap chain is ...



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

The greatest way to live with honor in this world is to be what we pretend
to be. -- Socrates
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