Nothing should depend on the known vulnerable multimedia/ffmpeg0. Either patch it to support modern ffmpeg or remove it. This project appears to be unmaintained upstream with the distfile only available from LOCAL/ahze so the second option would probably be for the best.
PLD Linux seems to have a bunch of patches for modern ffmpeg support if the port really should be preserved: https://git.pld-linux.org/?p=packages/mpeg4ip.git;a=tree
A commit references this bug: Author: riggs Date: Sun Jun 2 10:14:25 UTC 2019 New revision: 503301 URL: https://svnweb.freebsd.org/changeset/ports/503301 Log: Mark DEPRECATED with expiration date 2019-06-15 Rationale: There has been no active development for several years. The port also depends on other outdated, unmaintained code, most notably ffmpeg0 which is also scheduled for removal on 2019-06-15. The functionality provided by this port is available through multimedia/ffmpeg, which is actively maintained. PR: 238093 Reported by: tobik Changes: head/multimedia/mpeg4ip/Makefile