[FFmpeg-devel] Extending AVOption system
Sun Jun 8 20:07:50 CEST 2008
On date Sunday 2008-06-08 19:53:07 +0200, Stefano Sabatini encoded:
> On date Sunday 2008-06-08 15:40:01 +0200, Michael Niedermayer encoded:
> > On Sun, Jun 08, 2008 at 10:38:31AM +0200, Stefano Sabatini wrote:
> > > On date Saturday 2008-06-07 15:12:37 +0200, Michael Niedermayer encoded:
> > > > Basically we need a fast and efficient way to make all the values
> > > > from a struct and the AVOption constants available to eval() and that
> > > > has to be alot faster than iterating over them once. It can surely be
> > > > done, if someone volunteers to do the work i can think about how it
> > > > can be done ...
> > >
> > > I'm interested, if you can elaborate more on this I can try to
> > > implement it as time permits. If it can help I have already a naive
> > > implementation of an hash container (which I'm going to post anyway on
> > > the libavutil hash container thread).
> > Get these darn hash tables out of your mind, they wont do any good here :)
> > Ok heres a design suggestion, in no particular order:
> > 1. Sort all AVOption table entries by name. (diego will love this as well)
> > 2. in av_set_string() go over the string and look up all [a-z_]* via bsearch()
> > in the avoptions array.
> > for each replace the string by the literal numeric value of the constant
> > from the AVOptions array, value from the struct or min/max/default of
> > the current option.
> > After that handle the string as it is currently.
> Michael, eventual applications which work with non sorted arrays
> won't work anymore with bsearch(), so I have to provide all the required
> ifdeffery to keep backward compatibility, right?
... or maybe would a major bump be OK? In this case while we are at it
I suggest to move opt.[ch] and eval.[ch] in libavutil.
> Also I'm thinking about introducing an option_count field in AVClass,
> this or we have to compute the options array lenght everytime.
FFmpeg = Frenzy and Foolish Meaningful Power EnGine
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