[FFmpeg-devel] [RFC] AVFilter Parser

vmrsss vmrsss
Thu Mar 27 00:24:30 CET 2008

On 26 Mar 2008, at 18:55, Vitor Sessak wrote:
> Well, I think here you really underestimating the differences between
> the two syntaxes. This is not good, because it can seriously confuse
> someone who is trying to follow the discussion.

No, I don't think I do. Unfortunately we seem to have had a  
communication difficulty: it is certainly not easy to discuss matters  
like this my email. Please read below:

>> I am using the following syntactic elements because I find them
>> intuitive, but there is nothing special about them, just a matter of
>> taste:
>>  - comma (,) for sequential composition --
>> 	F,G implies #outstream(F) = #instream(G)
> Well, this is a very big difference between my syntax and yours. In my
> syntax a comma compose two filters (not two streams) linking one or  
> more
> streams between them.

Where did I say streams? I wrote: comma is for sequential composition  
of FILTERS. F and G are filters. The I wrote that writing F and G  
implies that the number of output streams of F equals the number of  
output streams of G. This is the same as you do...

>> - star (*) for parallel composition --
>> 	#instream(F*G) = #instreams(F) + #instream(G)
>> 	#outstream(F*G) = #outstreams(F) + #outstream(G)
> Same thing, in mine a star puts two filters (not streams) in parallel.

So does mine. And I added: the number of input (output) streams of F*G  
is the sum of the number of input (output) streams for F plus the  
number of input (output) streams of G.

>> ATOMIC_STREAM ::= all the streams in avfilter, eg crop, vflip,
>> scale, ...
> I'm not sure I understand what you call a stream. "crop" is a filter,
> with one input pad and one output pad. You can say that in a graph it
> gets an input stream and an output stream.

Oops, just a typo: I meant to write ATOMIC_FILTER of course, all the  
filters defined in avfilter.

I'll reply to the rest of the questions in a separate messages.

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