Advertisers have embraced video ads and many are pouring more and more of their digital budgets into them, but it turns out that they suffer from the same viewability problem that has plagued their display ad cousins.

That’s according to a newly-published study conducted by one of the biggest ad companies, Google, which says that 46% of desktop and mobile video ads it serves outside of YouTube never had the chance to be seen.

Of the unviewed ads, 76% never appeared on screen and the other 24% didn’t meet the Media Rating Council’s standard for viewability, which considers an ad to be viewable if it is half in view for at least two seconds.

Ads fare better on premier video property, YouTube, where 91% meet the Media Rating Council viewability standard and as far as payment goes, advertisers purchasing ads through Google’s TrueView offering only pay for an ad if it is watched for 30 seconds.

But even if companies like Google and Yahoo are providing advertisers with video ad products that require a certain level of engagement before an advertiser is charged for a video ad, advertisers should consider the Media Rating Council’s standard for viewability sets a very low bar.

That means billions of video ads, including those that are technically viewable, aren’t really been seen in any meaningful way, if at all.

So what are advertisers to do? Google says that viewability is highest on tablet and mobile devices, and that 300×250 video ads have the lowest viewability.

According to the search giant:

Advertisers seeking viewable impressions should look at high viewability sites that engage in best practices for video viewability. In general, advertisers should consider investing their spend in inventory comprised of larger video ad sizes to enhance viewability.

That advice seems sensible, but given the ridiculously low standard that has been set for viewability and the prominent role video is playing in many digital marketing mixes, it seems all but certain that video ad viewability will become a bigger much bigger topic in the near future.