On-demand video is on the rise, with channels like Hulu, YouTube and other services reporting record subscribers. This, in turn, has attracted a number of advertisers to shift more towards video ads, in the hopes of reaching an audience more effectively than in print.

That said, the results can still be somewhat mixed. Mediapost recently reported the findings of a recent study that indicate just how successful some video ads could be. And while YouTube continues to have a strong average viewability with 91 percent (compared to the rest of the Internet with 54 percent), some ads never really find the exposure that advertisers are looking for.

The study shows that, even with popularity rising on mobile devices, 46 percent of video ads are never seen, and 76 percent of non-viewable ads never have the chance to be seen by an audience. The study, released this past week, indicates that video ads that aren’t seen tend to run in the background, hidden behind another open web page. The remaining 24 percent of ads apparently scrolled off-screen, or were left abandoned in a time frame of less than two seconds.

Google has measured a lot of these ads as of late, placing them strategically so they have some form of exposure, and determining the length of time that they run so they can effectively be seen by viewers.

According to the study, a viewable video impression takes place when at least 50 percent of an ad’s pixels are visible on-screen for at least two seconds. This comes from the Media Rating Council and Internet Advertising Bureau (IAB) standard.

However, player size and position really make all the difference when it comes to exposure. Video ads are more viewable on mobile devices compared to desktop, with 83 percent of videos accounted for on said devices, 81 percent on tablets, and 53 percent on desktops.

Meanwhile, more than half of YouTube’s overall views come from mobile devices, with a high count of 94 percent on mobile and 87 percent more viewable on desktop.

It just goes to show that some companies may need to find a way to make their video ads more effective, in the hopes of gathering a user’s attention instead of simply running in the background. With the rise in video popularity, it’d probably help to find a way sooner rather than later.