Underrun

Underrun refers to a condition in which the available input data, material, or resources are insufficient to sustain a process, leading to a stall, glitch, or incomplete output. It is the opposite of an overrun, where the system receives more data or demand than it can handle.

In digital systems and multimedia, a buffer underrun is a common form. If a processor or storage subsystem cannot deliver data to an audio or video device quickly enough, the device may starve for data, producing pops, clicks, dropouts, or pauses. Causes include high CPU load, slow or fragmented storage, or jitter in data arrival. Mitigation strategies include larger or more robust buffers, real-time scheduling, faster storage, and prefetching or streaming architectures.

In streaming, real-time communications, and gaming, underrun describes a failure to meet timing deadlines due to insufficient data supply, resulting in playback glitches or processing delays. Similar issues can arise in other time-sensitive applications where data must be delivered within strict windows.

In manufacturing and logistics, underrun can denote a shortage of input materials or components required for production, potentially causing idle time, stoppages, or missed schedules, or a mismatch between demand and supply.

Preventing underruns typically involves ensuring adequate buffering or prefetching, maintaining reliable supply chains, and conducting timing analyses to meet deadlines, along with monitoring to detect early signs such as buffer depletion or inventory shortfalls.