[Matroska-general] Re: USF Specs (was Where do we go...)

Yusaku yusaku at anime.cz
Thu May 6 10:06:55 CEST 2004

>  > About USF support in matroska :
>  > Well, i honestly hope unmei will have the necessary time and motivation
>  > to look at that one day,
> Where are you living ? in China or what ? ;)
> He is already working on it :p
> http://usf.corecodec.org/usf_0.17proposal4.html

I took a glimpse at the specs and the DTD, and I must say that IMO at
current state it lacks the most in the area that has the biggest potential
to gain from XML format - the ammount of text effects usable is relatively
small - basicaly scale, font weight, outlines, shadow.

Ok, my random thoughts:

Even at current ASS specs implementation, the format allows for wider
palette of effects due to a lot of functions. Functional approach is very
bad idea for XML, though, so I would propose adding a 4D OpenGL style
transformation matrix of 16 float numbers to the "fontstyle" element. With
default matrix (1 on diagonals, 0 elsewhere) the rendering would work as
before. With different coefficients, the position, rotation, size, side etc.
(all possible stretchings, movings, ...) could be realized without the need
for zillions of rotation and scaling functions. Possibly also make some
matrix aliase names (like "MirrorByXAxis") and aliases with smaller matrices
with only some parameters to be filled left (rotate by X degrees in
direction of x/y/z) for people using notepad and not graphic editor - but
after some experience 4D matrices are not too evil, so it is just optional.
The implied matrice algebra is quite neat (already have nice effect but need
to rotate it to fit on shopsign in scene? Just multiply by position/rotation
matrix - currently IMPOSSIBLE in ass)

scale-x and scale-y could be dropped, absolute positioning could be left as
override for final positioning for effects (redundant, but convenient).

This way, defining of style like "Star wars banner text" would be possible
without too much trouble (major pain in ASS, although possible)


PS: I hope unmei is reading this - I do not have his email...

PPS: Having 3D control over integrated SVG would be quite neat as well -
imagine the effect possibilities ;)

PPS: Reread #3 - rotation is possible even now, but having the matrice as a
parameter of "PositionAtributeList" instead of current set of random
parameters copying ASS would be neat - there are a lot of possible
positionings not covered by current list

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