Read below for the simple solution!

Example of embedded WordPress standard FLV movie player.

Original clip is 400 x 300 – Displayed here at 500 x 400

Is WordPress able to play FLV movies?
As far I was aware the reply should be positive but then the practice is not.
I’ve tried different times but I was never able to properly embed a single movie using the internal “Insert embedded media” function.

This is quite strange cos WordPress actually (2.7 and newer) include an FLV movie player but the Embed Media function doesn’t seem to be able to setup the whole thing correctly.

Prepare it
The first time you have to copy the FLV movie player from
“wp-includes/js/tinymce/plugins/media/img/flv_player.swf”
to your blog base directory and rename it as “flvplayer.swf” (this is done for easier referring to the player file name).

Then you can use it this way

Select and Copy this code snippet:

-
Add a new Post  and switch the editor to HTML mode.
Paste the code snippet.
Configure the parameters.
Switch to Visual mode.
Save the post.

How to configure it.
Replace blue code with the complete url of your own blog base directory.
Replace green code with the complete url of the FLV file.
Replace violet code with the complete url of the alternate image (you can remove the “startImage” option if you plan to use the “autoStart” option or you don’t want the alternate image).
Red code is the FLV Player options so you can change them or remove unwanted ones (all options description are available here: FlvPlayer).

• flvToPlay = url to FLV file to load and play.
• autoStart = true or false. Default is true. If the flv should start loading/playing directly(true). Or if the the user has to interact before it starts to load/play.
• loop = true or false. Default is false. If the movie or playlist should loop or not.
• hiddenGui = true or false. Default is false. Makes the gui hide when no mouseMove event has occured for 1500ms.
• smoothVideo = true or false. Default is false. If the movie should be smoothed(interpolated). Can make scaled up videos look less pixelated.
• showScaleModes = none,double or full. Default is full. Determines how the video scales, none means it will not scale beyond it’s orginal width and height, that are read from the metadata of the flv. double, means it will scale up to twice of it’s original size. full, means it will scale up as much as it’s possible. But it will always keep the correct aspect ratio. If there isn’t enough room to scale to for example the double size, it will scale as much as possible, but it will keep the correct aspect ratio.
• defaultVolume = int, 0-100. Default is 100. The volume in %, the player will have when it loads. 0 beeing mute and 100 being full volume.
• startImage = url to image(jpg,gif,png,swf). If autoStart is set to false, an image can be loaded, like a preview of the movie. This has no effect if autoStart is set to true.

Give it a couple of tries and you’ll find it’s quite simple to setup and run the whole thing correctly.

Why do you want use it?
There are more powerful players around the net, I know, but I think the standard one is still useful when you have to manage a blog which don’t need many plugins and you want have a good compromise between optional components and integrated ones; plus you don’t have to worry about WP/Plugins upgrades and you don’t waste resources. This is better than nothing!
Do you need a more powerful player?
Well just download and install one of the many available plugins.