Replaying the same fifteen-second clip on every channel makes the load reproducible, but it can also synchronize the expensive parts of the workload. For the helmet classifier, all eight streams may reach their busiest target count at the same time.

I would repeat the staircase with phase offsets between streams and with a deliberately synchronized crowd burst, retaining crop counts alongside the FPS floor. Those two runs would show whether capacity depends on aggregate average demand or short classifier bursts. That complements your distinction between task-frame updates and accelerator invocations without treating eight passing channels as a universal hardware limit.