The FLV serving solutions discussed in this article require that the FLV files be encoded with metadata. Essentially, the server-side solutions need to be able to send FLV data from the point requested by the client, and in efficient increments. This information is stored in metadata, in the FLV file itself, in the form of keyframe time and position values.
Modern video encoders add this information during the encoding process. Additional tools, including Burak's great FLV Metadata Injector and Norman Timmler's flvtool2, can inject the metadata into preexisting FLV files. This information is discussed in detail, including sample source files, in my previous DevX article, "Flash Video: Don't Forget the Metadata."
It should also be noted that new FLV streaming alternatives are being developed that may not rely on metadata. One example is XProjects's xAsset PHP module. It is still in beta, I have not tested it, and it's unclear whether or not it is free. Metadata is a good thing and, with modern encoders doing this work for you, it's not difficult to add. However, you may wish to learn more about xAsset and other solutions that may exist if you have a large library of older FLV files.
The next installment of this video series will expand on the ActionScript in this article. In addition to connecting to your choice of streaming or progressive download assets, you will be able to script a feature-rich video controller.
Please let me know if you found this overview helpful, if you have any interest in additional coverage of the Flash Media Server, or if you have any questions about the alternatives discussed herein. Finally, as usual, let me know if you put this information to work for you. I'd like to see the results!