improve meta callback implementation

gst/cgo_exports.go

@@ -58,7 +58,13 @@ func goBusFunc(bus *C.GstBus, cMsg *C.GstMessage, userData C.gpointer) C.gboolea
 }
 
 func getMetaInfoCbFuncs(meta *C.GstMeta) *MetaInfoCallbackFuncs {
-	return registeredMetas[glib.Type(meta.info._type)]
+	gapi := glib.Type(meta.info.api)
+	gtype := glib.Type(meta.info._type)
+	typeCbs := registeredMetas[gapi]
+	if typeCbs == nil {
+		return nil
+	}
+	return typeCbs[gtype.Name()]
 }
 
 //export goMetaFreeFunc

gst/gst_buffer.go

@@ -188,7 +188,7 @@ func (b *Buffer) Map() *MapInfo {
 //
 // Example
 //
-//     metaInfo := gst.RegisterMeta(glib.TypeFromName("GstObject"), "my-meta", 1024, &gst.MetaInfoCallbackFuncs{
+//     metaInfo := gst.RegisterMeta(glib.TypeFromName("MyObjectType"), "my-meta", 1024, &gst.MetaInfoCallbackFuncs{
 //         InitFunc: func(params interface{}, buffer *gst.Buffer) bool {
 //             paramStr := params.(string)
 //             fmt.Println("Buffer initialized with params:", paramStr)

gst/gst_meta.go

@@ -107,8 +107,9 @@ type MetaInfoCallbackFuncs struct {
 	TransformFunc MetaTransformFunc
 }
 
-// Register metas internally as well so we can track callback functions
-var registeredMetas = make(map[glib.Type]*MetaInfoCallbackFuncs)
+// Register meta callbacks internally as well so we can track them. Not all
+// GstMeta callbacks include userdata.
+var registeredMetas = make(map[glib.Type]map[string]*MetaInfoCallbackFuncs)
 
 // RegisterMeta registers and returns a new MetaInfo instance denoting the
 // given type, name, and size.
@@ -127,7 +128,10 @@ func RegisterMeta(api glib.Type, name string, size int64, cbFuncs *MetaInfoCallb
 		return nil
 	}
 	wrapped := wrapMetaInfo(metaInfo)
-	registeredMetas[wrapped.Type()] = cbFuncs
+	if registeredMetas[api] == nil {
+		registeredMetas[api] = make(map[string]*MetaInfoCallbackFuncs)
+	}
+	registeredMetas[api][name] = cbFuncs
 	return wrapped
 }