well, regarding the following messages, I suspect that the missing dependency is libiconv, unfortunatelly, libiconv.ipk doesn't exist for i686 at least.
root@synology:/opt/bin# mkvmerge
mkvmerge: error while loading shared libraries: libicudata.so.56: cannot open shared object file: No such file or directory
root@synology:/opt/bin# ldd mkvmerge | grep not
libicudata.so.56 => not found
libicui18n.so.56 => not found
libicuuc.so.56 => not found
well, regarding the following messages, I suspect that the missing dependency is libiconv, unfortunatelly, libiconv.ipk doesn't exist for i686 at least.
root@synology:/opt/bin# mkvmerge mkvmerge: error while loading shared libraries: libicudata.so.56: cannot open shared object file: No such file or directory
root@synology:/opt/bin# ldd mkvmerge | grep not libicudata.so.56 => not found libicui18n.so.56 => not found libicuuc.so.56 => not found