IAI CFVE flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Chain of custody

A documented, unbroken record of who handled the video evidence, when, and for what purpose, from seizure to courtroom, used to prove integrity and prevent tampering.

Hash value

A fixed-length digital fingerprint (e.g., MD5 or SHA-256) computed on a video file; identical hashes before and after copying prove the copy is bit-for-bit identical.

Native file acquisition

Copying the original video file in its original format and container from the source device or DVR, preserving all metadata and avoiding re-encoding or screen capture.

Frame rate

The number of video frames displayed per second (fps); needed to convert frame counts to elapsed time and to detect dropped or duplicated frames.

Time base

The reference clock for video timestamps, either absolute (real-world date/time from the device clock) or relative (elapsed time since recording started).

Pixel aspect ratio

The ratio of a single pixel's width to its height; non-square pixels in DVR video distort measurements unless corrected to square pixels before analysis.

Interpolation

A digital enlargement method that estimates new pixels between existing ones; it improves display size but adds no real detail and cannot recover unrecorded information.

Photogrammetry

The technique of deriving real-world measurements from video or images by accounting for camera position, lens distortion, and perspective using known reference objects.

Lossless export

Saving video using a codec that preserves every pixel exactly (e.g., FFV1) or a visually lossless high-bitrate codec, so the exported copy retains evidential detail.

Metadata

Embedded file information such as creation date, device model, duration, and codec settings; it supports authentication but can be altered and must be verified.

Dropped frames

Frames missing from a video stream due to recording or storage limitations; they create time gaps and must be documented because they affect timeline reconstruction.

Re-encoding artifacts

Visual errors such as blocking or blurring introduced when a video is compressed again; they can obscure detail and may indicate the file is not the original.

Working copy

A duplicate of the original video used for analysis and enhancement; the original is preserved unaltered, and the working copy's hash is recorded.

Viewing guide

A document accompanying exported video that lists key timestamps, describes what occurs, and explains any edits or enhancements made for court presentation.

Lens distortion

Optical warping (barrel or pincushion) caused by a camera lens; it bends straight lines and must be corrected before measurements or identification comparisons are reliable.

Frame extraction

Saving a single frame from a video as a still image; the frame should be exported losslessly and its source timestamp recorded for reference.

Timestamp drift

Gradual error between a device's clock and true time; it accumulates over recording duration and must be quantified to align video with other evidence.

Container format

The file structure (e.g., MP4, AVI, proprietary DVR format) that holds video, audio, and metadata; it determines how the file can be read and exported.

Codec

The algorithm (e.g., H.264, H.265, MJPEG) used to compress and decompress video; knowing the codec helps predict artifacts and choose compatible analysis tools.

Authentication

The process of establishing that a video is what it purports to be, unaltered since recording, by examining metadata, hashes, continuity, and device records.

Continuity

The property that a video recording has no unexplained gaps, jumps, or discontinuities; breaks in continuity must be explained or flagged as potential tampering.

Enhancement

Processing such as brightness, contrast, or sharpening applied to improve visibility; it must be documented and reversible, and it cannot create detail that was never recorded.

Original evidence

The first-recorded video file or the device's native output; it is preserved unmodified and serves as the reference against which all copies are compared.

Bitrate

The amount of data used per second of video; higher bitrate generally preserves more detail, while low bitrate causes compression artifacts that limit analysis.

Resolution

The pixel dimensions of a video frame (e.g., 1920x1080); it sets the maximum detail available and cannot be increased by enlarging the image.

Frame numbering

Assigning a sequential number to each frame from the start of the file; it provides a precise, reproducible way to cite a specific moment in the video.

Time-lapse recording

A recording mode that captures frames at intervals slower than real time; playback speed differs from real time and must be accounted for in timeline analysis.

Audio track

The sound component of a video file; it can provide timing cues or evidence but may be recorded on a separate clock and must be synchronized and verified.

Screenshot capture

Taking a picture of a video display; it is generally unacceptable for evidence because it loses metadata and resolution, and should be avoided in favor of native export.

Proprietary DVR format

A manufacturer-specific video file format that often requires the vendor's player or converter; conversion must be documented and the original retained.

Calibration object

An object of known size in the video scene (e.g., a license plate or door) used with photogrammetry to convert pixel measurements into real-world units.

Report documentation

A written record of every step taken: acquisition, hashes, tools, enhancements, and findings; it allows another examiner to reproduce the analysis and supports testimony.