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LEVA Level 1 > General Definitions > Flashcards

General Definitions Flashcards

1
Q

Hash

A

A fixed-length, statistically unique identifier or digital fingerprint generated by running the data from the object being hashed through an algorithm

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2
Q

IFrame

A

Intraframe - least compressed frame, most information, refers to itself, denotes beginning/end of GOP

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3
Q

Container

A

A container format (informally, sometimes called a wrapper) or metafile is a file format that allows multiple data streams to be embedded into a single file, usually along with metadata for identifying and further detailing those streams. The Format or Container, stores the audio, video, subtitles, and other elements that make up your video

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4
Q

Codec

A

The Codec encodes and compresses, then decodes and decompresses the data that makes up your video. It is about what comes out of the camera; the filming and recording process.

Identified by the container; installed to the OS and called by the player when file is loaded; affects how multimedia appears during encoding

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5
Q

Pixel

A

Picture element - the basic unit of programmable color on a computer display or in a computer image

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6
Q

8-bit

A

A mode where the image uses 256 shades of red, blue, and green respectively, for a total of 16.8 million colors

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7
Q

True color

A

When all three RGB colors are combined in each pixel in 8-bit mode, 16.8 million different colors are possible (if each channel was lowered by one bit, there wouldn’t be enough possible shades to mimic human eyesight)

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8
Q

16-bit

A

Uses 16 channels per RBG color per pixel; means over 281 trillion color possibilities

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9
Q

Histogram

A

A graphical representation of tonal values in a digital image; used to understands contrasting values of black (0) and white (255) in an image

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10
Q

Frame averaging

A

A technique where multiple images are averaged out to remove random noise; best when target isn’t moving

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11
Q

Interpolation

A

The creation of new pixels that did not exist before resizing, based off existing pixels

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12
Q

Nyquist theory

A

Says to accurately recreate an analog signal, the signal must be sampled AT LEAST TWICE the highest frequency contained in the signal; prevents dropped frames during multimedia capture

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13
Q

Authenticity

A

Is the video an accurate representation of the area/scene/environment?

Depends on what issue the evidence is intended to answer

Authenticity is dependent upon what the evidence is supposed to represent

Florida Vs muro

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14
Q

Integrity

A

Is the video unchanged from acquisition/have all steps to clarify the evidence been documented

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15
Q

Extraction

A

The process of recovering data from its native environment

FVA must determine most accurate/best preservation method for each digital video, which methods they have in their toolkit

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16
Q

Preservation

A

The process of insuring evidence is not lost or altered
Challenges - possibility of overwriting, physical barriers, passwords, authority/consent

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17
Q

Analysis

A

The process of performing clarification techniques and drawing conclusions from clarified images

18
Q

Rods

A

Photosentive cells responsible for monochromatic vision; concentrated on periphery of retina

19
Q

Cones

A

Photosensitive cells responsible for color vision; concentrated in center of retina; classified by wavelengths they are sensitive to

Short wavelength cells - blue sensitive
Medium wavelength cells - green sensitive
Long wavelength cell - red sensitive

20
Q

IP camera

A

Internet Protocol cameras digitizes (samples and quantizes) values from a CCD or CMOS, compresses resulting images, and streams video using internet protocols; usually have built-in web servers; generally encrypted so only intended audience can view them

21
Q

Native resolution

A

Fixed grid pattern of LCD monitor; number of pixels wide by pixels high

22
Q

Pixel matrix

A

Configuration of pixels in a digital image or displays; ex: 1920x1080 is pixel matrix for 1080 tv with a 16:9 aspect ration

23
Q

Cloud

A

A cloud computing model that stores data on internet through a cloud computing provider who manages storage as a service

24
Q

Edge storage

A

Data stored within camera

25
Q

Centralized local storage

A

A hub/router/removable storage device

26
Q

Compression

A

The process of reducing the size of a data file OR the process of reducing the volume of data required to store/transmit info

Eliminates redundancy/discards less important data

27
Q

Lossless compression

A

No data is lost/all data can be retrieved in original form

28
Q

Lossy compression

A

Compression in which data is lost and cannot be retrieved in original form

29
Q

Quantization

A

Allows us to group like coefficients together

Quantization matrix is used to divide the DCT matrix; result is rounded to nearest integer

Stored with image so process can be reversed

WHERE THE MOST COMPRESSION/LOSS OCCURS

30
Q

Entropy encoding

A

Used to reduce size of data

Information is transformed from two dimensions to one by recording values of matrix in a zigzag pattern

31
Q

Spatial compression

A

Compression which uses similarity of pixels close in proximity to each other; applied within a single i-frame

32
Q

Temporal compression

A

Compression which takes advantage of similarities between frames close in time; applied to each frame in a GOP

33
Q

PFrame

A

Predictive frame which requires info from a preceding i or P frame, divided into macroblocks

34
Q

BFrame

A

Bidirectional frame which references the closest two I or P frames

35
Q

Artifact

A

Error caused by compression; things that are added or missing from video during compression

36
Q

Integrity

A

Is the evidence complete and unaltered since the time of acquisition?

Lack of integrity indicates unknown change to evidence, which can compromise the ability to prove its authenticity

Clarified evidence should be able to be verified against original evidence (by documenting steps needed to recreate process)

37
Q

Quantization noise

A

The difference (error) between original analog signal and signal produced from digitized values

38
Q

Clipping

A

Occurs when a signal falls outside minimum or maximum values that can be represented during quantization; results in a loss of contrast

39
Q

Aliasing

A

Occurs when sample rate is less than adequate to accurately reproduce signal

40
Q

Preservation request

A

Sent to obtain cloud video footage for 90-180 days

41
Q

Macro block

A

Group of pixels operated upon as a unit

LEVA Level 1 (4 decks)

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