Help : can't play some flv files downloaded with rtmpdump

[franck59]

I used rtmpdump with sucess for dowloading streaming webcam from some sites.
But when i capture from adult friend finder, something strange happens.
Some videos are ok and can be read as usual.
Others (maybe 50%) can't be read with all the flv players I tried (flv player, vlc, windows media, totem, gnome player...).
The only player wich shows anything is mediaplayer classic on windows seven, but it seems as if there was a v sync or hsync pb (most black or some time a glimpse of a picture). Others stall on the first picture. Totem has the message : stoppé (flux) (in french sorry).
Anybody has a clue? Is it a special protection patern which would only allow the videos to be seen in the embedded player in the site ?

What video codec is used in the problematic files? Have you tried to repair downloaded FLV files?