Updated from 7:55 a.m.Comcast ( CMCSA) posted strong second-quarter numbers Wednesday, saying its profit margins were better than expected. And, as Wall Streeters had speculated, the Philadelphia-based cable operator doubled the size of a $1 billion stock-repurchase program it initiated last December. Comcast said it has already bought $750 million worth of stock under the earlier billion-dollar buyback plan. Still, Comcast shares slipped 2% early Wednesday as the company trimmed its expectations for the scope of its basic cable operations. Cable exec Steve Burke said he thought the low end of the cable industry had reached "equilibrium," as measured by Comcast's latest-quarter loss of basic subscribers and reduced year-end target. Later, an executive at rival cable giant Time Warner ( TWX) made similar comments. The remarks suggest that the companies may redouble their efforts in coming months to market basic cable service, a business they'd largely ignored in recent years amid a push to cash in on more lucrative advanced digital services. On Wednesday, Comcast dropped 51 cents to $28.23. For the second quarter ended June 30, the nation's largest operator of cable TV systems reported earnings of $262 million, or 12 cents a share. That reverses the year-ago loss from continuing operations of $93 million, or 4 cents a share. Latest-quarter earnings eased past the Thomson First Call estimate of 10 cents. Revenue rose 10% to $5.07 billion, beating the $5 billion Wall Street consensus estimate. Operating income before depreciation and amortization -- among cable stocks, a more closely watched figure also known as ebitda or operating cash flow -- jumped 21% from a year ago to $1.95 billion, compared to analysts' expectations of $1.86 billion. "Cable's strong second quarter results and improved outlook for the remainder of the year reflect robust growth in new video and high-speed Internet services as we deliver compelling video services like Comcast ON DEMAND and HDTV and as we continue to expand the features offered to our high-speed Internet customers," CEO Brian Roberts said. "We are also generating significant operating improvements and scale efficiencies that are driving Operating Cash Flow growth and improving operating margins. We are reporting cable operating margins of nearly 40% for the second quarter -- well ahead of our expectations. This strong performance demonstrates our continued operational success in the acquired cable systems and the ability to leverage our scale. Cable-only revenue rose 10% to $4.84 billion; analysts had been expecting it to come in just below $4.8 billion. Cable operating cash flow came in at $1.92 billion, up 20%.