Translation for iptables raw rules that targert rtsp / Conntrack helper,

Hello all,

I've setup nf_nat_rtsp / nf_conntrack_rtsp to handle iptv flow from my 
internet provider.
This now work ok, but to make it work correctly, I need a rule like this 
one in the firewall:

     iptables-nft -t raw -A PREROUTING -p tcp --dport 554 -j CT --helper 
rtsp

So If Issue this command, everything is working of.
The matter is that I don't know how to translate it to put in my 
firewall.nft file.

nft list ruleset give me something like:

# Warning: table ip raw is managed by iptables-nft, do not touch!
table ip raw {
         chain PREROUTING {
                 type filter hook prerouting priority raw; policy accept;
                 tcp dport 554 counter packets 0 bytes 0 xt target "CT"
         }
}

If i put something like

table ip raw {
         chain PREROUTING {
                 tcp dport 554 -j "CT"
                 tcp dport 554 counter xt target "CT";
         }
}


I've got an error on loading:

nft flush ruleset; nft -f /etc/nftables/main.nft
     /etc/nftables/main.nft:380:27-40: Error: unsupported xtables compat 
expression, use iptables-nft with this ruleset
       tcp dport 554 counter xt target "CT";

I've also try the following syntax:

table ip raw {
         chain PREROUTING {
                 type filter hook prerouting priority raw; policy accept;
                 tcp dport 554 counter ct helper rtsp;
         }

}

This is loading ok, but have no effect.
Can someone point me the good way to target the rtsp conntrack from 
nftables ?

Thanks,

        Laurent.