It’s April, so it must be Mip-TV.The traveling circus that is the international TV distribution business has arrived in Cannes for the 30th anniversary edition of the Marche International des Programmes de Television (to give its full French title), which opens today and runs until Wednesday. Organizers report 1,877 companies registered to attend, up from 1,782 at the same time last year. One hundred countries will be represented, compared with 97 in 1992. As in previous years, companies from the United States, the United Kingdom and France form by far the biggest contingents. The hectic schedule of seminars, press conferences, cocktail parties and dinners packed into the next six days seems to offer optimistic signs that the business is back on the upswing after a flat year or two. Not only do companies have things to announce, they have money to spend. New York-based Worldvision is shipping in a glitzy lineup of six film directors, including Peter Bogdanovich, Jean-Luc Godard, Werner Herzog and Ken Russell, to launch its six-hour epic “Momentous Events: Russia in the ’90s.” Each helmer directed one hour of the series. Continuing the Russian theme, Britian’s Central TV and Maryland Public Television have commandeered a Russian warship to publicize their six-hour series, “Sea Power: A Global Journey.” Central will separately unveil a new production deal with Columbia TriStar Intl. TV. U.S. documentary specialists will vie for attention, with Discovery, Time Life TV and National Geographic all here in force. Discovery has 40 exex housed in a massive and elaborate new stand decked out to simulate a rain forest, complete with rushing waterfall and animal noises. Time Life TV, which announced a $ 30 million investment fund for original programming at last October’s Mipcom, will hold a party to tout the first fruits of that venture, “Time Life’s Lost Civilizations,” a 10-parter for NBC that is being sold overseas by London-based Itel. Time Life is expecting to finalize another major production deal within a month. But it remains unclear whether the frenzy of activity planned for the next six days indicates a genuine renewed buoyancy in the international TV business or is instead a desperate response to a marketplace that is becoming tougher and more competitive with every month.