[MPlayer-dev-eng] Re: [PATCH] vo_xvmc - bob deinterlacing

[Ivan Kalvachev]

2006/8/11, Guillaume POIRIER <poirierg at gmail.com>:
> Hi,
>
> On 8/11/06, Tomas Janousek <tomi at nomi.cz> wrote:
> > Hello,
> >
> > Tomas Janousek napsal(a):
> > > I've made it detect the right parameters from the stream and deinterlace
> > > it if needed, so I removed the bobdeint parameter. Patch attached.
> >
> > Has anybody looked at this patch? Is there something wrong I should fix?
> > Or any other reason to reject?
>
> As written in DOCS/tech/MAINTAINERS, Ivan is the maintainer of this
> code. He's the one who will eventually review and apply your code.

Sorry for the delay.
We talked on irc. here I document it for the maillist.

The changes done to xvmc_render.h are not necessary. This file should
contain only things needed for communication between codec and
vo_xvmc.

In the code that determines which filed to show first you also process
REPEAT_FIRST_FIELDS, that is only used on progressive picture for
telecine. That would only degrades visual quality.

Nearly half of the patch is about setting display_flags correctly from
mpi->flags, and then decoding display_flags to set correctly variables
first_field/second_filed. There must be simpler way.

Now I am really surprised that the bob without timing worked. There
are 2 explanations for it:
1. fields are switched on retrace so the first filed is actually shown.
This however could nearly-work with monitor framerates close to the
video field rate (aka mpeg2 30fps -> monitor 60Hz). With higher
refresh rates the difference between both fields would become more
visible. (BTW notice that by default XFree/Xorg doesn't provide modes
bigger than 85Hz, that's not so far away from 60);

2. When 2 fields commands are shown one after another, the last one is
in effect. That would be equivalent of skipping one fields.

Of course these things may be determined by experimenting. I'm gonna
do when i get little time to code ;)

BTW. I think the proper solution would be to modify decoder so it
could output fields and double the framerate. That would allow and
bob-deinterlace on software decoder.