As online video matures, the buying and selling of ads alongside it increasingly resembles the old television model, reports Mediaweek.

One of the biggest changes amongst high-profile sites is the adoption of a model based on impressions delivered, along with guarantees a goal will be reached. ABC and MSNBC have switched to that model from a flat-fee model that was more indicative of experimentation with advertising in streaming video.

Delivery of videos is still something that's up for grabs. MSNBC, for instance, guarantees a number of impressions but limits the ads a viewer is exposed to in a period of time so as not to create a frustrating experience. Sites are tweaking what models suit them best: pre-roll, interstitials or some mix thereof.

Most online video players expect the more familiar buying structure to increase the rate at which TV ad dollars are shifted to online, which is concurrent with viewer habits.

But universally accepted metrics are still needed to turn online video into a formidable brand-engagement option.