Computer Science 3

Basic values or facts

Data

Reducing the amount of space needed to store a piece of data

Data Compression

To digitize the signal, we periodically measure the voltage of the signal and record the appropriate numeric value. Instead of a continuous signal, we have a series of numbers representing distinct voltage values. Thus, we have a sample of the original continuous signal.

Define sampling as it relates to digitizing sound waves.

Spatial video compression removes redundant information within a frame. This type of compression is good for landscapes in which there are large blocks of color that are the same such as a blue sky.

Describe a situation in which spatial video compression would be effective.

A discrete representation of data

Digital Data

The act of breaking information down into discrete pieces

Digitize

No

Do vinyl record albums and compact discs record sound the same way?

Temporal video compression uses the differences between frames as the basis for compression. A key frame is stored in its entirety and then changes from that key frame are stored

Explain temporal video compression.

False

Four bits can be used to represent 32 unique things.

Replacing a frequently used word with a single character

Keyword Encoding

True

Keyword encoding replaces frequently used words with a single character.

a data compression algorithm in which there is no loss of information.

Lossless Compression

the data can be retrieved without losing any of the original information

Lossless compression means

data compression techniques in which some amount of data is lost. This technique attempts to eliminate redundant information.

Lossy Compression

Several different media types

Multimedia

a situation where a calculated value cannot fit into the number of digits reserved for it

Overflow

True

Overflow occurs when the value that we compute cannot fit into the number of bits we have allocated for the result.

Individual dots used to represent a picture; stands for picture elements

Pixels

Variation in a signal that jumps sharply between two extremes

Pulse Code Modulation

Storing image information pixel by pixel

Raster Graphics

The act of reasserting an original digital signal before too much degradation occurs

Reclock

The number of pixels used to represent a picture

Resolution

Replacing a long series of repeated characters with a count of the repetition

Run Length Encoding

False

Run-length encoding is very good at compressing english text

An alternative floating-point representation

Scientific notation

Number representation in which the sign represents the ordering of the number (negative and positive) and the value represents the magnitude

Signed-magnitude representation

Movie compression technique based on the same compression techniques used for still images

Spatial Compression

Movie compression technique based on differences between consecutive frames

Temporal compression

a representation of negative numbers such that the negative of I is 10 raised to k minus I

Ten's complement

Indexed color

The GIF format uses what technique?

True

The MP3 audio format discards information that cannot be heard by humans

Signed-magnitude representation

The representation for numbers you've used since grade school is called _________

True

The signed-magnitude representation of numbers has two representations for zero

True

The unicode character set includes all of the characters in the ASCII character set

Representation of an image in terms of lines and shapes

Vector Graphics

True

Vector graphics represent images in terms of lines and geometric shapes

Methods used to shrink the size of a movie

Video Codec

Video codecs

What are the techniques called that shrink the sizes of movies?

White

What color does an RGB value of (255, 255, 255) represent?

Color

What do we call the perception of the various frequencies of light that reach the retinas of our eyes?

Color depth is the amount of data used to represent a color; that is the number of bits used to represent each of the colors in the RGB value.

What does color depth indicate?

Digitizing is the act of breaking continuous information into discrete pieces so that we can represent each piece separately.

What does it mean to digitize something?

Raster-graphics format

What format stores information on a pixel-by-pixel basis?

RGB stands for Red, Green, and Blue. The RGB value is actually three numbers that indicate the relative contribution of each of these three colors.

What is an RGB value?

A signal that jumps sharply between two extremes

What is pulse code modulation?

Resolution refers to the number of pixels used to represent a picture.

What is resolution?

JPEG

What is the best format for photographic color images?

HiColor uses 16 bits; TrueColor uses 24 bits.

What is the difference between HiColor and TrueColor?

A lossless data compression is one in which no information is lost. A lossy data compression one in which some information may be lost.

What is the difference between lossless and lossy data compression?

Vector Graphics

What is the format that describes an image in terms of lines and geometric shapes?

The ASCII character set uses 8 bits to represent a character; the Unicode character set does not specify a fixed number of bits, but the most used encoding for Unicode does use 16 bits to represent a character. Thus while ASCII can represent 256 characters this mapping of Unicode can represent over 65000 characters. ASCII is fine for representing English, but the designers of Unicode wanted it to be able to represent all the world's characters. ASCII is a subset of Unicode.

What is the main difference between the ASCII and Unicode character sets?

40,000

What is the sampling rate per second that is enough to create reasonable sound reproduction?

Indexed color

What is the technique in which an application supports only a certain number of specific colors, creating a palette from which to choose?

Higher sampling rates produce better sound quality.

Which produces better sound quality, higher sampling rates or lower sampling rates?

Computers are discrete, finite machines. Analog information is continuous and infinite. Thus, computers cannot represent analog information directly; the analog information must be converted into a digital form.

Why do computers have difficulty with analog information?

Data compression refers to reducing the amount of space needed to store a piece of data. Although computer storage is relatively cheep, as the amount of data keeps increasing rapidly the cost of storage is a factor. However, the most important reason for compressing data is that more and more we share data. The Web and its underlying networks have limitations on bandwidth that define the maximum number of bits or bytes that can be transmitted from one place to another in a fixed amount of time.

Why is data compression an important topic today?

Analog

______ data is a continuous representation of information.

Digital

___________ data is a discrete representation of information.

A representation of a real number that keeps track of the sign, mantissa, and exponent

floating point

The dot that separates the whole part from the fractional part in a real number in any base

radix point

graphics and images with few colors

what are GIF files best for

True

An RGB value represents a color using three numeric values.

Sampling

An audio signal is digitized by _____ its value at regular intervals

True

An audio signal is digitized by sampling it at regular intervals

A continuous representation of data

Analog Data

True

A CD stores audio information in a binary format

False

A computer must use the binary number system to represent information

False

A computer represents information in an analog form

True

A digital signal represents one of two values at any point in time

False

A keyframe is used in temporal compression to represent the changes from one frame to another.

The number of bits or bytes that can be transmitted from one place to another in a fixed amount of time

Bandwidth

True

Bitmap, GIF, and JPEG are all examples of raster-graphics formats.

A list of the characters and the codes used to represent each one

Character set

The size of the compressed data divided by the size of the uncompressed data

Compression ratio

Most video codecs are block oriented; each frame of a video is divided into rectangular blocks

How are the various video codecs alike?

A human ear transmits vibrations that cause nerve impulses. The brain interprets these impulses as sounds of varying frequencies

How do humans perceive sound?

If enough pixels are used (high resolution) and presented in the proper order side by side, the human eye can be fooled into thinking it's viewing a continuous picture.

How does pixel resolution affect the visual impact of an image?

Any real value can be described by three properties: the sign (positive or negative one), the digits in the value with the radix point assumed to be to the right, and the exponent, which determines how the radix point is shifted relative to the mantissa. A real number is represented in the computer by storing it as an integer along with information showing where the radix point is.

How is a real value stored in the computer?

16

How many things can be represented with 4 bits

32

How many things can be represented with 5 bits

64

How many things can be represented with 6 bits

128

How many things can be represented with 7 bits

True

Huffman Encoding uses variable length binary strings to represent characters

Frequency of Use

Huffman codes are created based on the ___________ of the character

Using a variable-length binary string to represent a character so that frequently used characters have short codes

Huffman encoding

Radix

If the number base is other than base ten, we call the decimal point the ____ point

False

In the ASCII character set, no distinction is made between uppercase and lowercase letters

False

Indexed color increases the number of colors that can be used in an image, and thus increases the file size.

Data that has been organized or processed in a useful manner

Information

A sweeping second hand is an analog device. The motion of the hand is continuous.

Is a clock with a sweeping second hand an analog or a digital device? Explain.

A stereo speaker is an analog device because it receives an analog representation of the sound wave from the stereo. The speaker receives the signal and causes a membrane to vibrate, which in turn vibrates the air (creating a sound wave), which in turn vibrates your eardrum.

Is a stereo speaker an analog or a digital device? Explain.

The two's complement is a way or representing fixed-sized numbers in memory. The two's complement of a number X is just -X in two's complement representation. If X is a positive number, the two's complement of X is negative, but if X is negative, the two's complement is a positive number.

Is the two's complement of a number always a negative number? Explain.