A recording device, such as a video camera, emits audio watermarks (e.g., audible tones, inaudible tones) and records audio watermarks emitted by other recording devices. The audio watermarks provide information (e.g., data) such as an identifier of the camera and the identity of the operate. Audio watermarks may further include time information such as a timestamp indicating the time that the audio watermark was emitted by the camera. Audio watermarks may be emitted and recorded at intervals while recording an incident. A processing system, such as a digital video and audio processing system, may receive video information and recorded watermarks from multiple recording devices. The processing system may use the audio watermarks recorded by each recording device to determine which recording devices were in the vicinity of an incident. The processing system may also use the audio watermarks to align (e.g., synchronize) the video recorded by the various recording devices. Alignment of recorded video may permit synchronized playback of the recorded video from the various recording devices. Alignment may further identify at what point during an incident a recording device began and terminated recording.