The Nielsen Company has bought a video analytics company  to help track how engaged viewers are while watching Web video content, Mediaweek reports.

The company Nielsen has purchased is GlanceGuide.

Both Nielsen and competitor comScore have dropped behind some newer rivals such as TubeMogul and Visible Measures, which also aim to report video analytics, the article says.

But GlanceGuide’s attentiveness-tracking angle may help give Nielsen an edge. "Nielsen executives expect that publishers will use GlanceGuide to gauge the success of online programming, while advertisers and agencies will use the company’s technology to monitor users’ responsiveness to Web video ad campaigns," according to the article.