Identification of an eccentricity in the date/time metadata of a PAL MiniDV recording.
A Phase-Alternation Line (PAL) Mini Digital Video (MiniDV) recording and camcorder were provided by the Law Society of Singapore for forensic examination. During visual analyses of the submitted recording and a test recording produced on the submitted camcorder, the number of occurrences of each unique date/time stamp varied from the nominal value of 25 frames (the frame rate per second of PAL recordings), within a range of +/-3 frames. This embedded date/time information is recorded in the digital bit stream along with the video and audio information and can be optionally displayed during playback. These visual observations prompted detailed analyses of the digital metadata of the recordings which consisted of locating the portions of the bit stream associated with the date/time information, and then identifying their redundancy characteristics, data structure, and encoding protocol. Automated scripts were developed using digital data analysis software to locate, extract, convert, and count all of the unique date/time stamps, and to provide an easily-viewable output of the results. The application of the scripting process to both the submitted tape and the test recording produced on the submitted camcorder revealed that the date/time information on each exhibited a nonstandard but consistent timing pattern, which confirmed the visual observations and provided evidence that the submitted recording was consistent with having been produced on the submitted camcorder.
Lacey
Douglas S
DS
BEK TEK LLC, 12115 Sangsters Court, Clifton, VA 20124-1947, USA. bektek@cox.net
Koenig
Bruce E
BE