[MPlayer-dev-eng] [libass] Ignore PlayResX/Y aspect ratio for font aspect ratio.

[Nicolas George]

Le duodi 2 fructidor, an CCXVII, Karl Blomster a écrit :
> Now, it could certainly be argued that this is an oversight in the  
> spec/implementation that should be fixed (in fact, I do agree that it 
> should be) but the problem is that if you change this behavior (there is 
> actually a patched version of VSFilter that can optionally change it) you 
> will break a large amount of existing scripts that assume that fonts are 
> always rendered at an 1:1 aspect ratio, before anamorphic stretching 
> occurs (like VSFilter does) and therefore do their own anamorphic 
> stretching with ScaleX/ScaleY in the styling. For example there is a lot 
> of anamorphic 16:9 scripts with ScaleX set to ~80% to compensate for the 
> fact that the text will be stretched ~121% horizontally on playback.

Ok, I see the problem. I had never met scripts that overcompensated for the
scaling of anamorphic content. That is a shame: such scripts will look
overly thin on settings that scale before rendering the subtitles, such as
vo=gl.

And, as I said, I have seen quite a few scripts that make the opposite
assumption (so that they look the same on various encodings of the same
content).

I believe this calls for an option. I think I can provide a patch adding:

-ass-font-scale-x k

With the following semantic:

- k > 0: horizontally scale fonts by k; k = 1 means the current (braindead
  but compatible) behaviour; k = 45/64 compensates for a 64/45 scaling (16/9
  PAL).

- k = -2: sets k according to PlayResX/PlayResY and orig_width/orig_height;
  this gives us the behaviour we had six months ago and that I liked.

- k = -1 (default): heuristic guess:

  - if any style in the script has ScaleX != 1, then behave as if k = 1
    (assuming that ScaleX is there to compensate for anamorphic content);

  - otherwise, behave as if k = -2

Does it seem acceptable? If so, I will start coding.

Regards,

-- 
  Nicolas George
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