Digital Media Lecture 2: SemesterOverview Georgia Gwinnett College School of Science and Technology Dr. Jim Rowan

Sampling The process used to convert continuous phenomena in the real world to discrete numbers stored on a computer But… this process makes an “alias” of the original; it’s an approximation of the original that does have faults These negative side effedts are called artifacts

Sampling artifact examples: With audio, one artifact is quantization hiss With video, one artifact is retrograde motion; wheels look to turn backwards Moving images: Film With images one artifact is posterization Images as piles of numbers: Bitmapped images: Dithering and posterization

Some sampling artifact causes One cause of quantization hiss is undersampling –Not storing enough different levels for each sample taken One cause of retrograde motion is undersampling –Taking too few images per second (too few samples) One cause of posterization is not having enough quantization levels –Not storing enough different levels for each of the samples taken

Sampling artifacts More on this later in the class

How do you store sound? Collect samples of the sound and play them back Store it as numeric codes (midi) and regenerated it from those codes But we will only deal with collecting samples in this class

How do you store images? There are two techniques we will discuss in this class Bitmapped images –Store the image as a collection of spots of light known as pixels Vector graphics –Store the image as a mathematical description of the objects in the image

Bitmapped image A collection of spots (pixels) of light

Vector graphics A mathematical description of the objects in the scene This image could be described like this: (x1,y1) (x2,y2) (255,0,0) (x3,y3) (x4,y4) (0,0,255)

Why are there two ways to describe images? Bitmapped images –The size of the file depends on how many pixels there are in the image –The content of the image does not affect the file’s size –But…. they do not scale well

Why are there two ways to describe images? Vector graphics –The size of the file depends on how many objects there are in the image –So… the content of the image does affect the file’s size –But…. they are scalable

A brief look at the Internet – –Let’s get started: Networking issues

A brief look at the Internet – –Let’s get started: Networking issues

A brief look at the Internet: How to request stuff – –Let’s get started: Networking issues Uniform Resource Locator (URL) Has 3 parts Protocol FTP:// SMTP:// Domain name Ends in.edu.com.gov.org Directory structure and the requested page /newStuff/index.html

A brief look at the Internet: How to request stuff – –Let’s get started: Networking issues Uniform Resource Locator (URL) Has 3 parts Protocol FTP:// SMTP:// Domain name Ends in.edu.com.gov.org Directory structure and the requested page /newStuff/index.html

A brief look at the Internet: How to request stuff – –Let’s get started: Networking issues Uniform Resource Locator (URL) Has 3 parts Protocol FTP:// SMTP:// Domain name Ends in.edu.com.gov.org Directory structure and the requested page /newStuff/index.html

A brief look at the Internet – –Let’s get started: Networking issues

A brief look at the Internet – –Let’s get started: Networking issues

A brief look at the Internet – –Let’s get started: Networking issues

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