Zebediah Figura (@zfigura) commented about include/wmcodecdsp.idl:
uuid(7e320092-596a-41b2-bbeb-175d10504eb6)
] coclass CWMVXEncMediaObject {}
+typedef float ChMtxType;
+[
- uuid(e7e9984f-f09f-4da4-903f-6e2e0efe56b5),
+]
This should have [local] and [object].