[FFmpeg-devel] Extending AVOption system

Stefano Sabatini stefano.sabatini-lala
Sun Jun 8 19:53:07 CEST 2008

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?

Also I'm thinking about introducing an option_count field in AVClass,
this or we have to compute the options array lenght everytime.

FFmpeg = Faboulous & Foolish Minimalistic Patchable EnGine

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