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.