[FFmpeg-devel] [PATCH v2 2/4] ffmpeg: Add display_matrix option

[Nicolas George]

Gyan Doshi (12022-08-17):
> It's not based on ffmpeg's 'internal representation'. All transform
> attributes are stored as a composite in one mathematical object.
> Evaluating the matrix values will need to look at all sources of
> contribution. So gathering and presenting all these attributes in a single
> option (+ docs) makes it clearer to the user at the cost of an initial
> learning curve.

I concur a single option might be more convenient. Especially since our
options system does not take into account the order of options: the
interactions between multiple options would be rather hard to explain.

OTOH, I do not like a dictionary-based approach, for the same reason:
you have to explain the order of precedence of options, and how
contradicting ones interact.

Might I suggest to adopt the syntax of the transform attribute of SVG?
Or a subset of it with a stricter syntax.

https://developer.mozilla.org/en-US/docs/Web/SVG/Attribute/transform

It requires writing a specific parser, but one that can be done with
sscanf():

if (sscanf(cur, "translate(%d %d)%n", &dx, &dy, &off) >= 2 && off) {
    translate_current_matrix(&mat, dx, dy);
    cur += off;
}

Regards,

-- 
  Nicolas George

-- 
  “I dont see why” isnt an argument. Proposing better is.
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