[any ANONYMOUS forum user]

I downloaded an flv video file and plays in the Applian FLV Player (http://www.applian.com/flvplayer/) perfectly, but the only problem is the video's duration is unknown. Is there a way i can fix this?

[Stream Recorder]

Just fix the duration of your FLV file (make it seekable):
Fix/repair flv files (make flv files seekable,playable,inject metadata,fix duration)

[YnotMax]

What about a website which request you to login to view their video? (of course in this case, you have account login)
I can't download from these site by using rtmpdump, Replay Media Catcher 4, GetFLV.
Any suggestion?

[Stream Ripper]

What about a website which request you to login to view their video? (of course in this case, you have account login)
I can't download from these site by using rtmpdump, Replay Media Catcher 4, GetFLV.
Any suggestion?

You need to be specific. URL Please?