Spaced repetition

Spaced repetition is a study technique grounded in the spacing effect — a robust finding from cognitive psychology that information is retained far better when reviews are distributed over time rather than massed in a single session. The classic algorithm, formalized by Piotr Wozniak in the SM-2 algorithm (1987) and implemented in tools like Anki, computes a growing inter-review interval for each item based on the learner's recall performance: easy recall widens the gap; failed recall resets it. For learning video specifically, spaced repetition changes the product architecture in important ways: rather than a learner watching a course once and moving on, the platform must schedule and surface review content — brief recall questions, short re-watch clips, or flashcard-style prompts — days and weeks after initial exposure. This requires a persistent learner model that tracks which concepts each individual has seen and how well they remembered them, plus a notification or scheduling mechanism to bring learners back at the right interval. The combination with microlearning is powerful: a microlearning library of short clips becomes a spaced-repetition system when the platform knows which clips relate to which concepts and re-surfaces them on a schedule. The engineering challenge is retention of learner context across sessions: the system must persist individual item-level memory state, which is richer than the simple completion flags that SCORM tracks. xAPI is the natural fit here, as each recall attempt can be recorded as a statement with timestamp, performance, and item identifier. The practical trade-off is engagement: spaced repetition requires learners to return repeatedly, and push notifications or email nudges are necessary to sustain the behaviour, adding a marketing-automation dimension to the platform.

The handbook · 7 volumes

Fora Soft Video Engineering Handbook

Spaced repetition brings learners back to short review clips days later, so those clips must load fast and resume at the right point. The seven volumes cover the full video stack; for review-driven courses start with Volume 3 on players, CDN caching, and QoE, with encoding for short clips in Volume 1 and clear audio in Volume 4. Written by Nikolay Sapunov, CEO at Fora Soft.

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