H.265 exports unreadable by Kap or Quicktime

[patrickrushton]

When I export a file from Kap using H.265 codec, the resulting file can't be opened in either Quicktime nor Kap. Also the file doesn't get a preview icon or quicklook in Finder.

This doesn't happen with H.264 codec files or H.265 files that have been encoded in other software (such as Clop)