[MPlayer-dev-eng] A proposal for the OSD

[Alban Bedel]

Hi,

As we all know the osd stuff need some work as the current system is
reaching it's limits. I alredy thought a bit about that before. My main
idea is to try to make use of hardware (ie vo) capabilities and have
something flexible. Here is what i come up with, it turn out that in
fact it shouldn't need a big amount of new code as most of the stuff is
alredy here. 
First a little ascii diag (if that pass the mail and can help you to
understand me ;)

        VD  -----> VF ---> VO
                   î
                   |
        OSD ---->  OF
         |
         +-----+
         |     |
        OBJ1  OBJ2


At the beginnig a format is set for the osd (this should later depend on
the subtitles decoder capabilities, etc). The format will uselly be RGB
or YUV be we should also be able to later support ascii and encoded spu.
After that objects are added to the osd following the user settings (an
object may be the timer or a subtitle decoder, etc). Some may fail if they
don't support the output format.
Then a filter chain is build like for the vf's. This chain contain
just plain normal video filter so all existing filter can be used. The
last filter of this chain will convert query_format/get_image/put_image
calls in query_osd_format/get_osd_image/put_osd_image calls in the video
chain.
If the vo have some special osd capability it will simply respond to these
calls. But if the vo doesn't support these calls vf_vo will have to
sometimes restrict the dr.
When dr to the vo is possible (for example when the decoder use a TEMP
buffer) vf_vo can just give the same image as osd_image. When dr is not
possible (for example when the image have the preserve flag) vf_vo will get
a TEMP buffer from the vo (this should be possible with all vo's ?),
copy the image to it and then give that as osd image.
Ok as most of the time the osd isn't shown at all it would be nice to know
before decoding if the osd need to display something or not. This way we
can restrict the dr only if that's relly needed.

Ok, blah, blah but no patch ;) Anyway i'd like to know what do you guys think
of that. Do you see any major flaw, or have any comments ? 

	Albeu