Australian media conglomerate Fairfax Metro Media has extended its existing relationship with Google DoubleClick’s Ad Exchange to focus on online video inventory. However, unlike most publishers, Fairfax is in the middle of trying to extend its ad platform, known as drx, to allow the company to buy — not sell — inventory tied to streaming video. Fairfax is one of the Pacific region’s largest publishers and among its holdings are two of Australia’s largest daily newspapers, The Age and The Sydney Morning Herald. Like publishers everywhere, the traditional revenue lines are declining and the company is looking for ways to strengthen its digital businesses, which include about 200 owned and operated online brands. Many publishers…