After video and/or audio data is captured at a smart device, the data is processed to determine if any potential event candidates are present. In some implementations, the data is initially processed at the smart device e. g. , video source 501 or camera 118 or 106. Thus, in some implementations, the smart device sends event candidate information, such as event start information, to the server system 164. In some implementations, the data is processed at the server system 164 for event start detection. In some implementations, the video and/or audio data is stored on server system 164 e. g. , in video and source data database 509. In some implementations, the video stream is stored on a server distinct from server system 164. In some implementations, after a motion start is detected, the relevant portion of the video stream is retrieved from storage e.