TalkTalk signs up too as the final free-to-air broadcaster gets on board
Channel 4 and ISP TalkTalk have signed up to the Project Canvas IPTV initiative.
The two companies join the BBC, BT, ITV and Five in developing the platform to bring on-demand content to the UK's televisions through broadband-enabled receivers.
Although Canvas is still awaiting approval from the BBC's independent regulator, the BBC Trust, it's pencilled in for a launch towards the end of 2010.
A Channel 4 statement said the broadcaster believes Project Canvas is "critical to the long-term future of subscription-free TV".
Channel 4's director of strategy Gill Pritchard added: "IPTV is set to become the next generation of TV and if Channel 4 is to continue to enhance its importance in a fully converged world it is key to be part of driving Project Canvas."
Senior director for TV at TalkTalk, Max Alexander, said the company believes Project Canvas will be of "great interest" to its customers.
In response to the announcement, the BBC's director of Future Media & Technology, Erik Huggers, wrote in a post on the BBC Internet blog that it "underlines the huge public and market interest" in the scheme.
He added that the organisations behind Canvas are now asking for expressions of interest from other companies to join the project.