[FFmpeg-devel] [RFC] AVFilter Parser
Sat Mar 22 23:44:57 CET 2008
On Sat, Mar 22, 2008 at 01:22:22AM +0100, Vitor Sessak wrote:
> > ------------------------
> > filter_id:
> > any alpha numeric string identifying a filter
> > parameters:
> > any string
> > filter_with_parameters:
> > filter_id
> > filter_id=parameters
> > Such a filter has a unique number of inputs and outputs.
> > input_redirector
> > num<id
> > redirects input from id from the right into stream num
> > id>num
> > redirects input from id from the left into stream num
> > The specified stream num is inserted thus there is 1 input more
> > for each input_redirector. The renumbering though is delayed after
> > all input_redirectors are processed.
> > output_redirector
> > num>id
> > redirects output from stream num into id rightward
> > id<num
> > redirects output from stream num into id leftward
> > The specified stream num is removed thus there is 1 output less
> > for each output_redirector.The renumbering though is delayed after
> > all output_redirectors are processed.
> I really like the redirector with num and id. But I don't see any point
> about the extra complexity of '>','<'. Is it only useful for
> user-defined graphs?
yes i think so, unless you want to reuse identifers ...
> Extensions based on other grammars suggested (which I'm mostly favourable):
> 1- Letting the comma link more than one pad
> Advantages: Simplify the syntax of some filters
> Disadvantages: Add to syntax complexity
> 2- Let the ';' be interpreted like vrmsss's '*'
> Advantages, Disadvantages: Same as (1)
> 3- Allow labels to optionally specify the source/destination stream number.
> Advantages: Nice simplifications, like instead of
> (in1) vflip (T1); (in2) (T1) picInPic (out)
> that would be equivalent to
> (in1) vflip (T1:0); (in2:0) (T1:1) picInPic (out)
> could be written, much more simply
> (in1) vflip, (in2:0) picInPic (out)
> and in this case the comma will link to the next available stream.
I also think these 3 are all a good idea.
And if these are added our different syntaxes have largely converged
what is missing from yours is the () to group ; vs , differently from
the default precedence.
Besides this the remaining difference would be
!() last stream feedback
< / > forward / backward links
() non directional links
I think we agree that the feedback operator is confusing, that leaves the
question how good / bad the directional links are.
Ive no strong oppinion on this, iam just curious which is better ...
> Well, I hope I helped clarify things, not add to confusion...
I wasnt confused so i cant comment on that :)
Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
While the State exists there can be no freedom; when there is freedom there
will be no State. -- Vladimir Lenin
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