After applying current ffmpeg.git as of May 25:  ae0f71a387f05be7ac90d545af4d3aeb8e1cca89  and applying Andrew's patches:

  0001-Add-check-for-nb_inputs-before-calling-avfilter_get_.patch
  0002-Same-possible-crash-fix-in-ffstreamaudio-for-dynamic.patch

  0003-Do-not-filter-out-dynamic_input-filters.patch

  0004-HACK-ffmpeg-8.0-build.patch

CinGG builds but none of the ffmpeg plugins work.  The Video plugins crash (did not try them all, but a few like F_boxblur) when added to the timeline and then click on "Show Controls.  The Audio plugins do not crash but you get the warning tone only when you play them (again, I did not try them all, but F_chorus was one of them).

I have not looked at the code yet, but most likely it is just an oversight in trying to get it to compile.

Also, line 77 in 0004-HACK-ffmpeg-8.0-build.patch has "#esle" instead of "else".