Render out your character animation as a series of png-images with just the character. If you use something like Sony Movie Studio Platinum, or other similar software (there also is freeware, but SMS in the older versions is dirt cheap and does the job), you can then create a movie sequence from the image series, and the video software will be able to merge it with your "base movie".
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Any decent compositing software should be able to do it.
Render out your character animation as a series of png-images with just the character. If you use something like Sony Movie Studio Platinum, or other similar software (there also is freeware, but SMS in the older versions is dirt cheap and does the job), you can then create a movie sequence from the image series, and the video software will be able to merge it with your "base movie".