Ep 4: SSAI vs CSAI

Mid-show, the screen freezes. A spinner turns. The ad never loads.

Client-side insertion, CSAI, means the player fetches ads. Server-side, SSAI, stitches them in first.

Ten thousand viewers of stream TV.example hit one mid-roll. With CSAI, every TV pauses the show, calls the ad server, reads the VAST, downloads the video, plays it. Slow TV or network? Spinner. With SSAI, a stitching server requests the ad for each viewer, picks a ready, transcoded copy, and splices it into the video segments. The TV plays one smooth stream, like broadcast. The catch is tracking. Ten thousand impressions now report from one server, which looks like invalid traffic. So VAST says stitchers must forward each viewer’s details, in X-Device-IP and X-Device-User-Agent headers.

Using SSAI? Ask your vendor: do requests and tracking calls pass the device IP and user agent?

Next: one CTV app, many supply paths.