FLVPlayer.hx:

import flash.display.Sprite;
import flash.net.NetConnection;
import flash.net.NetStream;
import flash.media.Video;

class FLVPlayer extends Sprite
{
    private var nc:NetConnection;
    private var ns:NetStream;
    private var video:Video

    public function new()
    {
        super();
        nc = new NetConnection();
        nc.connect(null);

        ns = new NetStream(nc);
        ns.play("flash.flv");

        video = new Video();
        video.attachNetStream(ns);
        addChild(video);
    }

    static function main()
    {
        var p = new FLVPlayer();
        flash.Lib.current.addChild(p);
    }
}

compile.hxml:

-swf9 flvplayer.swf
-main FLVPlayer