Video start failure (VSF), also written video startup failure, is a session that attempted playback but terminated with a fatal error before any frame appeared. It is the bluntest QoE signal of all, because a failed start is a viewer who got nothing, and it is among the failure metrics defined by CTA-2066 alongside exits before video start and mid-stream playback failures. It is measured as a share of play attempts from player events, the error firing before the first playing event, and is distinct from a viewer voluntarily abandoning during the wait, which is exit-before-video-start. Its catch is the survivorship trap it exposes: because a session that never starts has no startup time to average, a service can report a tidy median startup while a tenth of sessions silently fail, so VSF must always be read beside startup time. A failure also poisons the next visit, cutting the chance a viewer returns within a week.
The handbook · 7 volumes
Fora Soft Video Engineering Handbook
Video start failure (VSF) counts sessions that delivered nothing at all, the worst outcome a viewer can have. Of our seven handbook volumes on the video stack, Volume 3 is the place to start for VSF, covering players and error recovery, DRM, CDN delivery, and QoE monitoring of start failures. Written by Nikolay Sapunov, CEO at Fora Soft.
Is a rising video start failure rate turning viewers away?
We will audit player errors, DRM and CDN logs to find why sessions fail to start and give you a fix list by impact. 250+ video products shipped since 2005.
