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Evaluating digital video transcoding for forensic derivative results
Walter E Bruehs1, Dorothy Stout2
1Federal Bureau of Investigation, Digital Forensic Analysis Unit, The Forensic Audio, Video and Image Analysis Program, Bldg 27958A, ERF-E, Quantico, Virginia, 22135, USA.
Journal of Forensic Sciences
|April 19, 2023
Summary
Video transcoding to MP4 format can degrade quality. This study found that transcoding settings, not software, cause quality loss. Awareness of settings is crucial for maintaining video data integrity.
Area of Science:
- Digital Forensics
- Video Analysis
- Data Compression
Background:
- Video data arrives in diverse formats and compressions, necessitating standardization for analysis.
- Transcoding to a common format, typically MP4, is standard practice in forensic and video analytic systems.
- Existing transcoding practices have led to observable variations in video quality.
Purpose of the Study:
- To investigate the causes of video quality differences during MP4 transcoding.
- To establish minimum recommendations for preserving video data quality during transcoding.
- To provide practical guidance for video analysts and forensic examiners.
Main Methods:
- Participants were tasked with transcoding provided video files into the MP4 format using their usual software.
- Transcoded videos were systematically evaluated using objective quality metrics.
- Analysis focused on identifying factors contributing to observed quality variations.
Main Results:
- Video quality degradation during MP4 transcoding is primarily influenced by user-selected settings, not the specific software used.
- Different transcoding settings significantly impact measurable video quality metrics.
- The capabilities of the transcoding program also play a role in the final video quality.
Conclusions:
- Practitioners must be aware of transcoding settings to prevent video quality loss.
- Informed selection of transcoding parameters is essential for maintaining data integrity for analysis.
- Adherence to recommended settings will ensure reliable video data for forensic examination and analytics.
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