Re-Recording Artefact
Definition
A visual or statistical signature introduced by pointing a camera at a screen playing back footage. Includes moiré patterns, screen reflections, temporal aliasing, and double-compression signatures.
- Cause
- Camera pointed at a playback screen
- Common signatures
- Moire patterns, screen reflections
- Also produces
- Temporal aliasing, double compression
- Relevance
- Video authentication and provenance
Common questions
Why would someone re-record footage off a screen instead of copying the file?+
Screen re-recording is sometimes used to strip or obscure metadata, evade file-format tracing, or repackage footage from a source the person cannot export directly, and each of these motives leaves the artefact patterns an examiner looks for.
How does an examiner distinguish a re-recording from a genuine original clip?+
They look for the compound signature of two capture stages: moire from the pixel grids interacting, a screen's refresh-rate mismatch causing temporal aliasing, and the compression characteristics of both the original encode and the re-capture layered together.
Related terms
- Bitrate Anomaly
- A departure from the expected relationship between scene complexity and compressed file size. Sudden drops, plateaux, or spikes in the per-second bitrate...
- Double Compression
- The condition in which a video has been encoded at least twice through a lossy codec. The term is also used loosely...
- Hash Verification
- The process of computing a cryptographic hash (SHA-256 or equivalent) of the exhibit file and comparing it against a previously recorded value...
- I-Frame (Intra-Coded Frame)
- A video frame that is encoded entirely from its own pixel data, without reference to any other frame. I-frames mark the start...
- P-Frame (Predictive Frame)
- A frame encoded as a set of changes relative to a preceding reference frame. P-frames are smaller than I-frames because they only...