The first major breakthrough in the two-month actors' strike, currently paralyzing the TV and movie industries, came early yesterday as negotiators programs shown on pay TV or sold on home video casettes . . .

This was the main issue in the 8-week-old strike called by the Screen Actors Guild and the American Federation of Television and Radio Artists, but other Important economic issues remain to be negotiated, including pay scales and the actors' share of residuals from reruns of programs in the one-hour, 90-minute and two-hour forms . . .

Nevertheless, federal mediator Tim O'Sullivan predicted that "this could mean the strike could be over in a few days" when he emerged yesterday morning from the marathon 15-hour bargaining session that ended in the breakthrough . . f

Although O'Sullivan refused to discuss details yesterday, a source close to the negotiations told us that under the tentative agreement actors will receive 4.5 percent of the gross receipts from pay TV after a program has been played on the air 10 times or after one year . . .

In addition, they will receive payment after the first 100,000 videocassettes or videodiscs of a program have been sold . . .

When the strike began, the actors had wanted 12 percent of the gross receipts from all home video programming . . .

The union membership will not be asked to ratify yesterday's agreement until after the rest of the negotiations are successfully concluded . . .

Reportedly, the unions are asking for a very large (perhaps as much as 35 percent) first-year raise in lieu of salary increases during the second and third years of the contract . . . While the movie and TV producers reportedly want to spread any raise over the length of the new contract . . .

Some 67,000 members of SAG and AFTRA have been on strike since July 21, delaying the start of the fall TV season and disrupting the filming of movies that had been scheduled for release this fall and during the big box-office holiday season . . .

Should the additional issues be resolved within the next few days, one network executive predicted yesterday that it would probably take a week or two for the unions to ratify the final agreement . . .

If that should happen, this executive predicted that TV viewers would have to wait until the last week of October or the first week of November to see the start of the 1980-81 season with new episodes of regular series . . .

Each taped TV show takes about three weeks to produce, once the cast and technicians are reassembled, while a film show takes about five weeks in production . . .

However, a further, key stumbling block remains in the path of final settlement of the current TV crisis . . .

The American Federation of Musicians, the folks who play the theme songs, etc., for television shows, have also been on strike during most of the past eight weeks, and their negotiations with the TV and movie producers are completely stalled . . .

Reportedly, both SAG and AFTRA had agreed early on the respect the musicians' picket lines, and if negotiations with the AFM don't get underway soon, the fall season may still be a long way off for viewers . . .