It has been a transformative year for video viewing on mobile devices, and with the increased uptake has come the gradual migration of ad impressions toward mobiles. The third quarter of 2015, however, saw ad impressions make a frenzied stampede into the mobile space, according to Ooyala’s latest quarterly Global Video Index. The findings show that tablets and smartphones together accounted for 46% of all online video ad impressions across broadcasters, publishers and networks during the previous quarter. PCs followed with 40% of all ad impressions, down 7% from Q2, and IPTV lagged with only 14%, down 9% from Q2. Publishers saw a huge gain for ad impressions on tablets during the quarter, up to 32% from 15%. Surprisingly, ad…