ASFChop is a command-line tool that you can use to delete parts of an .asf file and to add indexing, script commands, markers, and general properties to an .asf file. Deleting parts of a file reduces the length of time required to stream the file. ASFChop creates an index for that file so that you can seek (similar to fast forward) through the file. Windows Media Encoder can also be used to create seekable .asf files. An .asf file must have at least 10 seconds of content to be indexed.