mpv @0.28.2_1 builds on mojave but video is blank

[Richard L. Hamilton]

The audio plays fine, and the window comes up the right size, but it's always black, with a variety of files (mp4, mkv, m4v, avi, swf, at least; what I had handy to try).

It worked back on High Sierra (same version of mpv, I think).  And I made sure I built ffmpeg with the same variants I'd had before, so that shouldn't be the problem.

0.29.1, which I probably downloaded from the mpv.io website, is working fine.

The library versions shown when using the --version option are identical for the MacPorts build and the downloaded build.

Do we need to switch to the current version?