To use several previews for a single source object you should create several MPreview (or MFPreview) objects. Here is an example:
MPlatform SDK
MPreviewClass prev = new MPreviewClass();
MPreviewClass prev1 = new MPreviewClass();
MFileClass m_objFile = new MFileClass();
prev.PreviewWindowSet("", panel1.Handle.ToInt32());
prev.PreviewEnable("", 1, 1);
prev.ObjectStart(m_objFile); // start the 1st preview
prev1.PreviewWindowSet("", panel2.Handle.ToInt32());
prev1.PreviewEnable("", 0, 1);
prev1.ObjectStart(m_objFile); // start the 2nd preview
MFormats SDK
You should create and configure 2 MFPreview objects and feed then with source frames. Note that you should use only one object to control the frame rate:
// preview frame with common object mySecondPreview.ReceiverFramePut(sourceFrame, 0, ""); // preview frame with master object that controls playback rate myMainPreview.ReceiverFramePut(sourceFrame, -1, "");