Flash Video (FLV) is a proprietary file format used to deliver video over the Internet using Adobe Flash Player (formerly known as Macromedia Flash Player) version 6, 7, 8, or 9. Flash Video content may also be embedded within SWF files. Notable users of the Flash Video formats include YouTube, Google Video, livevideo.com, Yahoo! Video and MySpace.
How to download/grab/record Flv video and audio through HTTP protocol
1.Click "Add" button 
and open "add URL to download" window
2.Input URL into "URL" editbox
3.Select "Flash Video Streaming" from "Streams" drop-down list.
4.Press "OK" button, HiDownload will add the URL to list and download it.