UPDATE 1-Comcast beats profit estimates even as it loses video subscribers

(Adds share buyback, dividend increase)

NEW YORK, Jan 24 (Reuters) - Top U.S. cable provider Comcast Corp's adjusted quarterly profit exceeded analyst estimates on Wednesday, helped by more high-speed internet customers and greater theme-park revenue.

Excluding the impact of a $12.7 billion one-time benefit following a U.S. tax overhaul signed into law in December, earnings per share were 49 cents, beating analyst estimates of 47 cents a share.

The Philadelphia company also raised its quarterly dividend by 21 percent to 19 cents a share, and said it expects to buy back at least $5 billion of its stock this year.

Comcast lost 33,000 video customers in the quarter ended Dec. 31, compared to an addition of 80,000 last year. The company's video business has been pressured by consumers canceling cable packages in favor of cheaper streaming options from companies like Netflix Inc.

Revenue grew 4.2 percent to $21.92 billion from a year earlier, roughly in line with analyst expectations of $21.82 billion, according to Thomson Reuters I/B/E/S.

Net income attributable to Comcast rose to $15.0 billion, or $3.17 per share, for the quarter, from $2.3 billion, or 48 cents a share. The company was able to book a gain on its deferred tax bill thanks to recently lowered U.S. corporate tax rates.

Revenue rose 3.4 percent in the cable business, which includes video, internet and voice services. Comcast added 350,000 high-speed internet customers in the quarter, compared with a gain of 385,000 the same period a year earlier.

NBCUniversal's revenue rose 3.9 percent in the quarter, helped by the segment's theme-park business. (Reporting by Anjali Athavaley; Editing by Bernadette Baum)