There are more digital video file varieties in surveillance video than any other form of digital video. The reason for this is because each manufacturer programs their own proprietary digital video format in order to keep their CCTV video recordings secure. When a crime has been committed and caught on video, the video forensic expert must decide the best way to acquire that proprietary video so that it can be used as evidence in court.
Most CCTV systems have export features. Video and images can be removed from the CCTV system easily and securely. This exporting feature is not always the best method from a forensic perspective. Exporting video from the CCTV surveillance system often compresses the digital video file too much for the video forensic expert to enhance. In order to enhance a portion of surveillance video the video forensic expert must start with the highest quality possible.
I have found through experimenting that screen capture programs like Camtasia can create digital video exhibits of much higher quality than many CCTV surveillance systems. Lately, for every case I investigate that requires digital video enhancement or clarification, I use both the CCTV system export (usually an AVI file format) as well as a screen capture from Camtasia to compare the quality.
Most law enforcement authorities use a screen capture method because it is faster at the scene of the crime to capture the video evidence instead of exporting.
I often realize that the compression that the proprietary player exports is not suitable for forensic examination and clarification. The system export resolution and bit rate are too low for a video forensic enhancement starting point.
On the other hand, I can set my screen capture specifications much higher for resolution and bit rate when recording the same series of events on the CCTV system video monitor. Camtasia has an HD option for exporting that dramatically increases the bit rate and data rate providing a much better starting point for enhancement and clarification. Because I have both the export and screen capture videos, there is no doubt about chain of custody and process documentation for my forensic report.
I will be creating a series of videos in the near future using Adobe Premiere Pro for video enhancement and clarification using both methods to further exemplify the necessity for both methods of evidence gathering.