[FFmpeg-devel] [RFC] AVFilter Parser

[vmrsss]

Hi Michael,

On 21 Mar 2008, at 21:02, Michael Niedermayer wrote:
> This one is quite similar to the previous proposals, the main  
> difference
> besides a clear definition of things is the feedback/feedforward  
> syntax.
> The new syntax avoids the often cited problem with string insertion of
> predefined filter graphs and name colissions.

Yes, we are converging, I like this much better, and I am glad the  
idea of user-defined filters has survived. I'll send a few questions  
and comments using Vitor's message which followed yours. Two things:

(1) Why not to had a conditional expression on filters parameters to  
do the kind of thing Vitor suggested a few emails ago:

> 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;
>     }
> }

at the filter-scripting/combination stage? Eg it could be:

filter ::= .... | conditional_filter

conditional_filter ::=  case(parameter) of v1 -> filter1 , v2 ->  
filter2 , .... , vk -> filterk

where v1, ..., vk are constants and all filter1,...,filterk have the  
same number of input and of output streams.

(2) is it OK to send a pdf attachment to the list? just in case one  
needs to draw a complex graph...