If anyones looking for the most compatible solution, the Sigma Real Magic is one of the most common MPEG decoder cards still available today. Originally using the feature connector then later using a VGA pass-through cable. Many ISA and PCI cards versions.

Winbond had a pass-through MPEG decoder (Winbond W99200), but not as common to find.

Many VGA cards only supported output on the feature connector (such as the Matrox cards). Many Cirrus Logic cards supported both input/output. Most mid-late 90's cards had at least hardware video scaling and colour conversion, offloading all but the actual MPEG decoding from the CPU.

Thx, because there is no slot free in my mystique machine with free feature connector, I will have to use something over VGA or something that routs directly over PCI bus (if such a thing exists).
But I already read in the WCIV forum that only the early boards from real magic work in wing commander 4 dvd version.