Systems and techniques for an automatic event recorder are described herein. An input stream may be written to a memory buffer in an overwrite mode. The input stream may be received from a sensor array of a wearable device. A first portion of the input stream written to the memory buffer may be protected upon obtaining an indication of occurrence of a start event. The memory buffer may be configured to receive a second portion of the input stream in a write mode subsequent to the occurrence of the start event. The memory buffer may be reconfigured to receive a third portion of the input stream in the overwrite mode upon obtaining an indication of the occurrence of the stop event.