About the MIME type
You can optionally specify a MIME type for the imported asset by using the mimeType parameter. If you do not specify a mimeType parameter, Flex makes a best guess about the type of the imported file based on the file extension. If you do specify it, the mimeType parameter overrides the default guess of the asset type.
Flex supports the following MIME types.
- application/octet-stream
- application/x-font
- application/x-font-truetype
- application/x-shockwave-flash
- audio/mpeg
- image/gif
- image/jpeg
- image/png
- image/svg
- image/svg-xml