Amazon is said to be planning a free ad-supported tier of its Prime Video service. But there’s very little detail on how much content it will cover.

According to AdAge, one option Amazon is exploring is that it would strike deals with content providers to be paid a share of ad revenue rather than a flat fee. It’s also exploring having these payments directly limited to the time customers spend watching each show. It’s also possible Amazon would share whatever demographic data it has about the people who watch each show, both with content makers and advertisers.

One likely problem is figuring out exactly what content to include in the service. It appears that TV shows and movies will be limited to older material, keeping more recent series as an exclusive for paid customers. There’s also likely to be an emphasis on lifestyle shows that have a more obvious opening for targeted ads.

The big downside is that the reported model doesn’t necessarily lend itself to high quality, particularly in scripted drama. Netflix content providers don’t get paid directly based on viewership and don’t get details of viewing figures, let alone a demographic breakdown. While that has its drawbacks, it means shows don’t have to be pitched or paced solely to maximize viewership.