[FFmpeg-devel] Support for metadata in libavutil/eval.c

Nicolas George george at nsup.org
Tue Jul 15 17:02:00 CEST 2014

Le quintidi 25 messidor, an CCXXII, Stepan Bujnak a écrit :
>					 Now, as far as I know the
> expression evaluation is now optimized to only work with double values,
> therefore the re-implementation of the expression evaluation to accept
> string arguments would not be trivial and so I ask you, would such
> functionality be helpful and welcome?

As far as I know, the eval code is not optimized much: it just parses the
expression into an abstract tree in memory with a lot of pointers.

I believe the eval code would greatly benefit from a complete modernizing,
both for usability and speed:

- constant sub-expressions simplification;

- rewrite the parser to have the full range of C operators: "a<b" instead of
  "lt(a,b)", "c?x:y" would be nice too;

- compile the parsed tree for the expression into some kind of bytecode
  would probably greatly enhance speed.

Adding support for string values can be done at the "rewrite the parser"

This is quite huge work, but really useful IMHO.


  Nicolas George
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