Bitrate Anomaly
Definition
A departure from the expected relationship between scene complexity and compressed file size. Sudden drops, plateaux, or spikes in the per-second bitrate can indicate that a segment has been replaced, re-compressed, or generated differently from the surrounding footage.
- Signal type
- Departure from expected complexity-to-size relationship
- Patterns seen
- Sudden drops, plateaux, or spikes
- Indicates
- Possible replacement, re-compression, or insertion
- Field
- Video forensics, authentication
Common questions
Why can a bitrate anomaly point to video tampering rather than just a scene change?+
A genuine change in scene complexity, such as motion starting or lighting shifting, produces a bitrate change proportional to that complexity. An anomaly is a mismatch between the visual content and the bitrate response, such as a flat bitrate during a visually busy segment, which suggests the segment was encoded separately from its surroundings.
Is a bitrate anomaly enough on its own to prove video manipulation?+
No. It is an indicator that prompts closer examination, such as checking frame-level compression artefacts or metadata continuity, because legitimate factors like a codec switch or a recording device change can also produce a bitrate discontinuity.
Related terms
- 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...
- Re-Recording Artefact
- A visual or statistical signature introduced by pointing a camera at a screen playing back footage. Includes moiré patterns, screen reflections, temporal...