[vlc-devel] Re: SVG rendering module - advice wanted

Sigmund Augdal sigmunau at stud.ntnu.no
Mon Apr 4 12:57:07 CEST 2005

On Mon, Apr 04, 2005 at 12:05:03PM +0200, Olivier Aubert wrote:
> Hi Sigmund.
> Thanks for the answer. Here are some comments.
> > I still fail to see why you want to use the text renderer api. Do you expect
> > printf() to render svg?
> I would reverse your sentence : I expect SVG to be able to render simple
> text, which my module does: it allows to specify a template, so that
> text is rendered any way you want.
> Anyway, the major reason for not defining another API is that the text
> API is (and already was, at the time I wrote the plugin) there. It is
> already a bit of work to add modules to the existing infrastructure, I
> do not have the time to design a new one. In my case, VLC is only a
> brick (albeit a major one) in an application, and I prefer to focus on
> the application itself, plus its documentation, plus research
> articles, ...  I will actively contribute to such an effort, but cannot
> lead it.
I can see your rationale, but I think it is both conter-intuitive, and a bit
misleading. And I think that if the svg module in any way performs worse
than the freetype module for the main-stream uses of a text rendering
module, then it is a bad thing. 

anyway, I'll try to describe/implement my theory if I get some spare time (I
have way too many balls in the air as it is).

> > Vlc's YUVA format uses equal resolution for all planes. You seem to
> > subsample the U and V planes.
> Yes, that solved the problem (committed into SVN). I did not see the
> annoucement for this change (as the same conversion code was working in
> 0.7.x), and could not grasp it from the video_chroma/ code.
I think it has been mentioned in a commit message or two, but I see there is
no obvious way to get that info. 

> > The subtitle timing properties are desided by whoever adds the subtitle to
> > the subtitle core. This means that the text renderer module cares nothing
> > about the subtitle timing. I don't know any part of the code that adds svg
> > subpictures, so I can't help proofread this part of the code.
> Well, I use VLC_showTextAbsolute/Relative to do this (interactively or
> from an external application, through either the CORBA control plugin or
> the python-vlc module that I will submit for inclusion one of these
> days). You can download the Advene application
> (http://liris.cnrs.fr/advene/) if you want to have a look at it.

the ShowText functions all have timing info parameters. Are these set
correctly? If the text is shown longer than the specified duration, or after
the specified stop time, that is a bug and should be investigated as such.
Could you send the complete log of such a run?


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