Cost-effective solution to synchronised audio-visual data capture using multiple sensors

Abstract

Applications such as surveillance and human behaviour analysis require high- bandwidth recording from multiple cameras, as well as from other sensors. In turn, sensor fusion has increased the required accuracy of synchronisation be- tween sensors. Using commercial off-the-shelf components may compromise quality and accuracy, because it is difficult to handle the combined data rate from multiple sensors, the offset and rate discrepancies between independent hardware clocks, the absence of trigger inputs or -outputs in the hardware, as well as the different methods for timestamping the recorded data. To achieve accurate synchronisation, we centralise the synchronisation task by recording all trigger- or timestamp signals with a multi-channel audio interface. For sensors that don’t have an external trigger signal, we let the computer that captures the sensor data periodically generate timestamp signals from its se- rial port output. These signals can also be used as a common time base to synchronise multiple asynchronous audio interfaces. Furthermore, we show that a consumer PC can currently capture 8-bit video data with 1024x1024 spatial- and 59.1Hz temporal resolution, from at least 14 cameras, together with 8 channels of 24-bit audio at 96kHz. We thus improve the quality/cost ratio of multi-sensor systems data capture systems.