RCA Corp. President Edgar H. Griffiths told shareholders today that the "very low ratings" of its National Broadcasting Co. subsidiary's programs this year will result in a sizable decline in NBC earnings in 1979.

But Griffiths said that programming whiz Fred Silverman's handiwork will be apparent with the fall programming schedule, and at that time "we will move forward."

NBC earned $122 million last year on sales of $1.2 billion compared with earnings of $152.6 million in 1977 on sales of $1.1 billion.

Two months ago, Griffiths said that NBC's profit slide was at an end and predicted that 1979 profits of the giant RCA subsidiary would be the same as in 1978 or slightly higher.

Despite the expected slide in NBC earnings, Griffiths predicted that RCA-which also owns Hertz, produces televisions, owns communications satellities, runs Random House, controls Banquet Foods and is a major record producer-would post record profits in 1979. Last year, the company had pretax profits of $515 million on sales of $6.6 billion.

NBC has been last among the three networks in ratings for the last four years, and the company lured Silverman - former programming chief at both ABC and CBS - last summer as president of NBC.

Indeed, while Griffiths conducted the three-hour stockholders meeting today, Silverman was clearly the star of the session, held in the same Rockefeller Center Studio from which Saturday Night Live emanates each week.

At one point, Silverman stood up from his seat in the crowded studio to answer a gruff shareholder's question about NBC programming. Silverman promised that some of the new shows being introduced now would catch on and pointed out that five of the 15 series introduced at mid-year will return next season, which he called "an above-average performance."

Silverman sat down to applause after Griffiths cautioned that the NBC president should not be abused.

Griffiths expressed complete confidence in Silverman and new NBC Chairman Jane Pfeiffer. He also said that Silverman is not a "miracle worker: He is merely by reputation and performance the finest programming man in this country based on his performance at two other networks."

A dark-horse - and defeated - candidate for director of RCA was Johnny Carson, the Tonight Show host who is trying to get out of an NBC contract that expires in the spring of 1981.

Professional shareholder Evelyn Y. Davis said that Carson would soon "qualify as an outside director," and proposed him as a substitute for Pfeiffer, whom she claimed was plotting with Silverman to oust Griffiths within the next two years.

Carson, who had no role in his nomination, garnered 302 votes to roughly 59 million for Pfeiffer. Carson, who appears three times a week on the five-nights-a-week Tonight Show and takes extended vacations, was opposed by another professional shareholder, Wilma Soss, who said he could not make 75 percent of the RCA directors' meetings as required by the rules.

Griffiths also told stockholders that, although RCA is interested in acquisitions in either the financial or electronics field, it is not engaged in any merger talks at present.

He also said that the company has moved into first place in sales of both color and black-and-white television sets for the first time since 1962. CAPTION: Picture, Fred Silverman, foreground, NCB's new head of programming, at meeting, UPI