How to Convert ASF to iMovie on Mac OS X(Lion included)
What is ASF file?
The ASF file type is primarily associated with 'Advanced Streaming Format' by Microsoft Corporation. Advanced Streaming Format is an open file format specification for streaming multimedia files containing text, graphics, sound, video, and animation. Advanced Streaming Format (ASF) does not define the format for any media streams within the file. It defines a standardized, extensible file container that is not dependent on a particular operating system or communication protocol, or on a particular method (such as HTML or MPEG 4) used to compose the data stream in the file.
An ASF file consists of three objects: a Header object containing information about the file itself, a Data object containing the media streams, and an optional Index object that can help support random access to data within the file. A number of programs capture this file extension.
How to convert ASF to iMovie on Mac?
Step 1: Free download ASF to iMovie Converter for Mac:Download Video Converter for Mac (Intel version) Download Video Converter for Mac (PowerPC version)

Step 2: Import ASF files to ASF to iMovie Converter for Mac and set the output format from the pull-down menu. Choose iMovie as the output format.

Step 3: Start the conversion, just click the button
to start converting asf to imovie.
After the process of converting ASF to iMovie compatible formats on Mac running Mac OS X Snow Leopard, Lion etc, you can import your ASF to iMovie successfully. By the way, more tips about how to edit ASF videos on iMovie are here.
