It's been predicted many times before and never happened, but this time it might just be true: television comedy is getting good again.

The first sign that something was happening was earlier this year when ITV – yes, ITV! – broadcast a good sitcom for the first time since, oh, Rising Damp. And it starred Derek Jacobi, Ian McKellen and Frances de la Tour. And it had some great one liners, such as Ian McKellen's reaction to finding himself in a crowd of young people. "Look at them all," he said. "Itching to get back on the internet."

The fact that ITV – yes, ITV! – was prepared to invest in a comedy in this way was an extremely good sign. In some ways, the situation bit of the comedy was old-fashioned but the characters – two elderly gay men – weren't and the writer certainly wasn't – it was the on-the-edge playwright Mark Ravenhill.

The new BBC sit-com Family Tree has a similar pedigree with even better results. The eight-parter was created by Christopher Guest, who was behind the wonderful comedy film Best in Show, set at a Crufts-style dog show. To call Guest the writer of Family Tree would be wrong though because it is largely improvised from plot outlines suggested by him.

The star Chris O'Dowd, who plays Tom Chadwick, has obviously taken to the improvisation and the result is wonderful. Chadwick is a man floating through the world – and realising it is full of idiots. Such as Ellie, a girl he ends up on a date with. "There are dinosaurs that still exist," she says. "Some people don't think so, but most do. There's been loads of sightings of dinosaurs in Africa. And there's the Loch Ness monster . Loch Ness is its name. That's why it's called Loch Ness."

It's no surprise that O'Dowd is funny although in recent years he had been breaking into movies and drama (he was splendid in The Crimson Petal and the White). Which leads to one of the other signs of hope for TV comedy: the calibre of actor it is attracting. In America, three new comedies have just been announced and they all star actors who in the dog days of TV comedy wouldn't have dreamed of doing a sit-com.

The first is Robin Williams, who hasn't appeared on television for 31 years and yet here he is playing a zany (what else?) dad in The Crazy Ones. This week, Michael J Fox also announced he was making a new sitcom and Philip Seymour Hoffman has signed on to do a comedy about an advertising agency. The last one in particular is likely to end up on British television before too long.

Other little signs of hope are easy to find. In two weeks time, for example, David Walliams will appear in a new sit-com set in a school. BBC3 is also investing heavily in new comedy and plans to premiere some of it on iPlayer rather than terrestrial TV.

It all suggests a bit of a revival and also that producers have finally learned how to make TV comedy. It will only last, though, if we all learn how to watch it. First, it's ok to go five minutes without laughing. Second, you've got to stick with a series because it takes time to get to know characters and laugh at them. And third, and most important: don't miss the laugh track. We don't need other people to tell us what's funny.