How sure are you the watermark is due to ecm?
Starting with a provider who will send video without watermark,I assume the watermark would be inserted by ird under certain circumstances.
The only way an ecm can trigger a watermark would be if there is a descriptor in the ecm that tells the ird to insert it.
I assume this is what you want to remove?
Can you decrypt the ecm?
Is this ND$?
You must post more information,decrypted ECM packets,a summary of what you know about the encryption,and more importantly,if you can decrypt the ECM.
Help yourself by posting what you know