Stroll down Princes Street on what passes for a summer day in Edinburgh and it is not long before flyers find their way into the hands of the unwary.

The top one may be from students promoting their badly written play, but it's more likely to be advertising a stand-up comedy show.

Stand-up is everywhere in Edinburgh, with audiences queueing for the best at a host of venues and sponsors keen to get in on the act. It's a vibrant scene that needs no subsidy or help to keep going.

Yet, talk about comedy on television, and the debate, when the laughter subsides, is somewhat different.

The question is whether the long, golden tradition from Fawlty Towers through Only Fools and Horses to The Office can continue with the same vigour as audiences fragment.

Viewers may yearn for good comedy, but they turn to sport, entertainment and drama far more easily, and commercial broadcasters find comedy difficult to crack. It leaves the field rather dominated by programmes funded by the licence fee, as if Britons need public intervention to be amused on a dark evening.

ITV has a particularly difficult problem. It requires a fifth of the available audience at any time to justify a show's place in the schedule, which perhaps explains why its only real scripted success is Benidorm.

Yet, Channel 4, where the audience hurdle is lower, perhaps two million at its peak, finds it tough, too. Comedy at Channel 4 is probably only a breakeven genre (with costs that can run to £350,000 a half hour, it can be expensive to make).

For all the cult status and success of Channel 4's Peep Show it has not broken through in the ratings. It pulls in a little bit more than a million viewers when it airs.

Every other channel bar those two and the BBC is irrelevant. Henry Normal, of Baby Cow (the makers of Gavin & Stacey), observes that you have only three people in Britain to whom you can sell your show.

Part of the problem with comedy is that it rarely rates well right away, and hit shows take a while to establish.

Take The Office, shown on BBC Two originally, it aired initially to modest audiences and it was not until the sixth episode of series one that BBC audience tracking suddenly realised that the approval rating for the programme had shot off the scale.

The series was given a quick repeat screening, and only then was it established as a hit. Other programmes have taken even longer than one series to break through.

It is often said that the BBC has the advantage of “nursery slopes” in Radio 4, BBC Three, BBC Two, with good shows finally making it to BBC One. That allows acts such as Little Britain to build a following or fail quietly.

That helps: at any one time the BBC is working on 40 to 50 television comedies, Lucy Lumsden, the BBC's head of commissioning for comedy, says. Yet, she, too, notes that just at the moment, the corporation lacks a BBC One hit, and there is a little less comedy on Britain's most-watched channel.

That may reflect only the creative cycle. It is also a reminder that no one is immune to the rising challenge of making mass-audience comedy work.

Fortunately for the nation's sanity, no one wants to concede defeat. Paul Jackson, who commissions comedy at ITV, says that comedy is crucial to a broadcaster, because audiences respond so positively to hits.

It is part of the reason why the BBC remains popular with the public, and ITV, which did not invest heavily in comedy even in the era of less competition, in the 1960s and 1970s, is less loved.

There are also new possibilities offered online. The BBC is revamping its comedy website for the new year and is thinking about commissioning short clips for the web.

That could prompt the creation of new types of comedy. One obvious form is the animated cartoon, which has Mark Freeland, BBC head of comedy, interested. For an example of what can be done, watch the weekly cartoon at Hits Daily Double, the music industry website. It may be geared towards industry insiders, but it helps to ensure that the site is required reading.

Perhaps this points to a new future where internet comedy can reach a more modest audience but, because it is cheaper to make, can be profitable, too.

That may mean, over the next decade, the number of mass audience British hits, such as My Family, will reduce, while the number of cult hits, such as The Mighty Boosh, will remain steady.

Stand-up comedy should remain resilient, as it, too, survives on lower audiences, although most Britons would struggle to name stand-up artists who have not yet appeared on television.

However, a move from mass to cult should be slightly troubling, too. On most people's definition of Britishness, humour comes near the top of the list - and it shouldn't be funded only by the licence fee (a levy that may yet be paying for Channel 4, too).

There is no crisis in comedy yet, but as sport seems to dominate ever more of the schedule, what happens in the next five years, as digital switchover completes, could be crucial. Keep laughing - otherwise we might all have to escape to the gym.

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