Rewrapping
Definition
Moving a compressed bitstream from one container to another without decoding it. Forensically equivalent to the original encoded stream; no new generation loss is introduced.
- Field
- Digital video and audio forensics
- Operation
- Container change without decoding the stream
- Effect on quality
- No new generation loss
- Contrast
- Transcoding decodes and re-encodes, causing loss
Common questions
How can an examiner tell if a video file was rewrapped rather than the original capture?+
Container metadata such as the muxer or writing application tag, timestamps, and structural box ordering in formats like MP4 can differ from the device's native output even though the underlying codec stream is bit-identical, giving a forensic indicator of a container change.
Does rewrapping affect the codec-level evidentiary value of a video?+
No, because the compressed bitstream itself is untouched, frame data, compression artefacts, and any codec-level authenticity indicators remain exactly as encoded, unlike transcoding which can introduce new compression artefacts.
Why would someone rewrap a video file instead of leaving it in its native container?+
Common reasons include compatibility with a target platform or player, reducing file size overhead from an unneeded container feature, or standardising a batch of files to one container for a review or evidence platform.
Related terms
- Codec
- A coder/decoder algorithm that compresses and decompresses media data. H.264/AVC and H.265/HEVC are the dominant video codecs; AAC and MP3 are dominant...
- Container Format
- A file format (MP4, MKV, MOV, AVI, MXF) that multiplexes video, audio, and metadata tracks into a single file with a defined...
- GOP (Group of Pictures)
- The repeating sequence of I, P, and B frames in an inter-frame compressed video. GOP size (the distance between I-frames) is an...
- I-Frame
- An intra-coded frame: a self-contained image compressed without reference to any other frame, like a JPEG. I-frames are the only random-access entry...
- Perceptual Coding
- Lossy compression that exploits psychoacoustic or psychovisual masking to discard information the human senses are least sensitive to. MP3, AAC, and AC-3...