General Definitions

Question 1

Hash

Answer 1

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

Question 2

IFrame

Answer 2

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

Question 3

Container

Answer 3

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

Question 4

Codec

Answer 4

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

Question 5

Pixel

Answer 5

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

Question 6

8-bit

Answer 6

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

Question 7

True color

Answer 7

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)

Question 8

16-bit

Answer 8

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

Question 9

Histogram

Answer 9

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

Question 10

Frame averaging

Answer 10

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

Question 11

Interpolation

Answer 11

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

Question 12

Nyquist theory

Answer 12

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

Question 13

Authenticity

Answer 13

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

Question 14

Integrity

Answer 14

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

Question 15

Extraction

Answer 15

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

Question 16

Preservation

Answer 16

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

Question 17

Analysis

Answer 17

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

Question 18

Rods

Answer 18

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

Question 19

Cones

Answer 19

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

Question 20

IP camera

Answer 20

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

Question 21

Native resolution

Answer 21

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

Question 22

Pixel matrix

Answer 22

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

Question 23

Cloud

Answer 23

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

Question 24

Edge storage

Answer 24

Data stored within camera

Question 25

Centralized local storage

Answer 25

A hub/router/removable storage device

Question 26

Compression

Answer 26

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

Question 27

Lossless compression

Answer 27

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

Question 28

Lossy compression

Answer 28

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

Question 29

Quantization

Answer 29

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

Question 30

Entropy encoding

Answer 30

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

Question 31

Spatial compression

Answer 31

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

Question 32

Temporal compression

Answer 32

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

Question 33

PFrame

Answer 33

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

Question 34

BFrame

Answer 34

Bidirectional frame which references the closest two I or P frames

Question 35

Artifact

Answer 35

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

Question 36

Integrity

Answer 36

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)

Question 37

Quantization noise

Answer 37

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

Question 38

Clipping

Answer 38

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

Question 39

Aliasing

Answer 39

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

Question 40

Preservation request

Answer 40

Sent to obtain cloud video footage for 90-180 days

Question 41

Macro block

Answer 41

Group of pixels operated upon as a unit