Interop vs SMPTE DCPs

Digital cinema rolled out before the standards body finished standardising it. The industry agreed an interoperable subset — Interop, often written IOP — so that rollout could begin. The formal SMPTE standards arrived afterwards and were better in several specific ways, but by then tens of thousands of screens were already running Interop packages.

The result is the usual one: a long, slow, incomplete migration. Both flavours are still in circulation, and the difference is invisible until it is not.

Ask for SMPTE unless you have a reason not to. Anything at 25fps — a good deal of European television-originated content, some event cinema, some archive transfers — cannot be an Interop package at all. Closed captioning for accessibility needs SMPTE. And the subtitle handling is genuinely better.

The exception is old hardware. A server that has not had a software update in a decade may handle Interop happily and SMPTE badly, particularly around subtitles. If you are running equipment of that vintage, test a SMPTE package on a quiet morning before booking a run on one.