This patchset resolves a number of issues in the current code:

 * Bogus doubles framesync initialization
 * Executing build_parameters on each input frame
 * Segfault when there's no secondary input (yet)

and adds a number of enhancements to bring this on-par with the other
overlay filters:

 * Enable pixel alpha blending
 * Expose framesync parameters
 * Add support for expressions in overlay parameters (x, y, w, h)

softworkz (11):
  avfilter/overlay_vaapi: use FILTER_SINGLE_PIXFMT
  avfilter/overlay_vaapi: build filter params just once
  avfilter/overlay_vaapi: remove double framesync init
  avfilter/overlay_vaapi: handle secondary null input
  avfilter/overlay_vaapi: reformat options
  avfilter/overlay_vaapi: remove redundant .get_buffer assignments
  avfilter/overlay_vaapi: add framesync options
  avfilter/overlay_vaapi: precalculate blend_state, enable pixel alpha
  avfilter/overlay_vaapi: enable expressions for overlay parameters
  doc/filters.texi: remove incorrect statement
  doc/filters.texi: update overlay_vaapi documentation

 doc/filters.texi               |  50 +++--
 libavfilter/vf_overlay_vaapi.c | 328 ++++++++++++++++++++++-----------
 2 files changed, 257 insertions(+), 121 deletions(-)

base-commit: f3b5277057ad84071721f01419fe4badeceaff08

Submitted-As: https://master.gitmailbox.com/ffmpegdev/pull.42.ffstaging.FFmpeg.1665399281.ffmpegagent@gmail.com