I have done this with static picture files over video and video over video.
I imagine that WMM will handle an animated gif just the same. You will need
to add a custom transition, but it is not hard to do.
1. copy the following text and save it as a text file in the "c:\Program
Files\Movie Maker\1033\AddOnTFX\" folder with a .xml extension.
NOTE: the actual directory may be different depending on your language (1033
is for English) and installation (you may have elected to install to a
location other than "Program Files"). You may also have to create the folder
AddOnTFX.
=========.xml file==============
<TransitionsAndEffects Version="1.0">
<Transitions>
<TransitionDLL guid="{C5B19592-145E-11D3-9F04-006008039E37}">
<Transition name="CromaBlue" iconid="91">
<Param name="KeyType" value="0" />
<Param name="RGB" value="0x0000FF" />
</Transition>
</TransitionDLL>
</Transitions>
</TransitionsAndEffects>
================================
2. The file I have given is for a gif file with a blue background (the
background will be transparent). In order for this to work, you have to know
the exact RGB values of the portion of the animated gif you want to be
transparent. The transition I have given treats all pure blue (RGB = 0000FF)
pixels as transparent. You will need to replace the value of the RGB
Parameter to match the actual value for the pixels you wish to be
transparent. Make sure to resave the .xml file after you make changes.
3. Restart WMM. Custom Transitions are loaded at run time, so you must
restart WMM before the transition will be visible.
4. Place the video clip on the time line.
5. Place your gif on the timeline after the video clip
6. Grab the gif and slide it over on top of the video clip to create a
transition between the two.
7. Open the transition collection and find the new transition you just
created (CromaBlue). Drag and drop onto the overlaped portion of the video
clip and animated gif.
The trick is to know the exact RGB value of the transparent pixels. If you
have created the gif yourself, this is probably easy to determine.
Another note. If the gif is stored with an alpha value to designate each
pixels transparency there may be an easier way. A KeyType value of 3 instead
of 0 prompts the transition to look at the alpha value instead of the RGB to
determine a pixels transparency. I have never tried this method so I don't
know how it works, but it may be easier than the RGB method. For more
information on the Key Transition including the alpha key, see:
http://msdn.microsoft.com/library/d...n-us/directx9_c/directx/htm/keytransition.asp
If you need to resize the gif, it will be easier to do it in the program
that you used to create the gif. Barring that, there is a way to do it in
WMM, but it involves more custom transitions and saving the movie at least
twice. Let me know if you want info on the WMM method for resizing the gif.
Hope this helps,
Ken