MFile, MPlaylist, MMixer and MLive
All the properties for MFile, MLive, MPlaylist, and MMixer objects require "object::" prefix. For example:
(myLive as IMProps).PropsSet("object::mirror", "horz"); // to mirror video horizontally
There are specific properties for MFile that starts with "file::" prefix. This is common for files that are MPlaylist items or MMixer streams (i.e. MItem objects). And
For MLive object, specific properties start with "device::" prefix. For example, for ScreenCapture engine:
(myLive as IMProps).PropsSet("device::capture.show_mouse", "false"); // to hide mouse pointer
And in this case, the properties are valid for the device that is exactly set. For example, if you set "device::vanc.capture_cc" property for Decklink Studio 2 device, then the effect takes place only for this device. And when you switch to another Decklink the property has a default value. If you prefer to set the property for all the devices, consider setting a property through system registry.
For MPlaylist there are just a few of such properties - "loop" and "dynamic":
(myPlaylist as IMProps).PropsSet("loop", "true"); // to loop the playlist
MRenderer, MPreview and MWriter
MRenderer, MPreview, MWriter objects properties are used without "object::" prefix. For example:
(myRenderer as IMProps).PropsSet("mirror", "horz"); // to mirror video horizontally
What about MFormats SDK?
Properties for objects in MFormats SDK do not require any prefixes.