Duncan told Broadcast the seven-day online rights window secured by the BBC would not work for C4, which commissions all its content from the independent sector.
At present C4 can only broadcast simultaneously online. "We need both simultaneous rights on any platform and a 30-day window during which we can play out that programme and continue to earn commercial revenue," he said.
After the agreed time period, Duncan believes there should be a "fair deal" to share further revenue. "The broadcaster is bringing a lot to the party in terms of the subsequent values of those rights," he added.
Duncan conceded that C4 was prepared to look at reducing longer term holdbacks on shows, which currently last up to five years.
But that is unlikely to appease Pact, which has developed its own set of proposals that have been discussed with Ofcom and are due to be presented to C4 at the end of the month.
Duncan confirmed that if C4 did not end up with a "sensible public service window and share of commercial revenues" it would ask Ofcom for permission to make its own shows.
He said: "It's an issue of survival. If C4 is going to survive in the future and the whole business model is going to work, I think we'd have no alternative but to build up our own in-house production."