The vdpau_mixer could fail to be recreated properly if preemption
occured at some point before playback initialization (like when using
--hwdec-preload and the opengl-cb API).
Normally, the vdpau_mixer was supposed to be marked invalid when the
components using it detect a preemption, e.g. in hwdec_vdpau.c. This one
didn't mark the vdpau_mixer as invalid if preemption was detected in
reinit(), only in map_image().
It's cleaner to detect preemption directly in the vdpau_mixer, which
ensures it's always recreated correctly.
Always configure the vdpau mixer based on the current surface sent to
it. Before this, we just hardcoded the chroma type, and the surface size
was essentially a guess.
Calling VdpVideoSurfaceGetParameters() on every surface is a bit
suspicious, but it appears it's a cheap function (just requiring some
locks and a table lookup). This way we avoid creating another
complicated mechanism to carry around the actual surface parameters
with a mp_image/AVFrame.
This factors out some code from vo_vdpau.c, especially deinterlacing
handling. The intention is to use this for vo_vdpau.c to make the logic
significantly easier, and to use it for vo_opengl (gl_hwdec_vdpau.c) to
allow selecting deinterlace and postprocessing modes.
As of this commit, the filter actually does nothing, since both vo_vdpau
and vo_opengl treat the generated images as normal vdpau images. This
will change in the following commits.
