MEXICO CITY, Oct 21 (Reuters) - Grupo Televisa (TLEVISACPO.MX), Mexico"s largest broadcaster, reported on Thursday a 77.3% drop in net profit in the third quarter compared with the same period a year earlier. The company posted third-quarter net profit of 760.6 million pesos ($36.8 million) compared with 3.350 billion pesos in the same period last year, falling short of the Barclays estimate of 933 million pesos. Televisa"s revenue grew 9.1% to 26.128 billion pesos, from 23.943 billion pesos in the year-earlier period. That was above a Barclays prediction of 24.5 billion pesos. Televisa and leading U.S. Spanish-language broadcaster Univision announced in April they would merge content through the creation of a new Spanish language media company, in which Televisa would be the largest shareholder. The new firm, called Televisa Univision, will launch a global streaming platform with content from both. Mexico"s telecommunications regulator, IFT, last month authorized the tie-up. The transaction is expected to close this year, Televisa said. In September, Televisa said the sale of its 40% stake in Ocesa Entertainment to U.S. firm Live Nation would move forward, a move that would support Televisa"s deleveraging efforts, according to S&P Global Ratings. ($1= 20.642 pesos at end-September)