[vlc-devel] Question about video filters - svg rendering

Olivier Aubert oaubert at bat710.univ-lyon1.fr
Thu Jan 6 16:12:04 CET 2005


I am trying to update the SVG rendering module that worked in 0.7.2 to
use the new filter API of 0.8.1. It should be much simpler now that
there is a blending infrastructure, but I think I did not quite catched
how it works.

What I do is basically (using freetype.c as model) :
- in the RenderText function, render the SVG data into a GdkPixbuf that
is stored in the associated subpicture_data_t
- in the Render function, copy the rendered GdkPixbuf to a new
subpicture region

It does not work (displays nothing), so here are my questions :

- I assume that the Render method is passed a subpicture that is meant
to be filled with regions holding supplementary data. The additional
regions are to be rendered into the final picture by the VLC
infrastructure. Am I deeply wrong ? 

In the previous version (the one that is still in svn:
module/misc/svg.c), I had to write the merging code myself, as I was
given a picture_t. I hoped (from what I saw) that the changes removed
this burden from the modules to the infrastructure. Here, a GdkPixbuf
happens to be a simple RGBA buffer, so I figured that I would simply
create a new region with a FOURCC RV32 and copy the pixbuf data to the
region's first plane.

- Is there any way for the filter_t* object to access the associated
video_output_t properties ? I need the width and height of the
video_output, as parameters for SVG rendering (and having matching
dimensions should speed the merging process).


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