C021TV-I1-S2

ICN : 1. Binary coding 1. Representation of information in the form of bits 2. To store images or sounds 3. Compression 4. Data organization 5. Data bases Introduction de la semaine 2/2 Présentation du sommaire global de la semaine : apparition progressive des éléments de la liste, puis mise en évidence de la portion concernée par la vidéo. Mise en évidence = police noire + gras Nom abrégé de cours - Enseignant

Pixels Video games, digital television, virtual reality, … Which technology for the display? Pixels (Picture Element) Composed of 3 colors Also used for manipulation, printing, etc.

Pixels coding Sequence of bits coding each pixel 1 bit per black and white pixel 8 bits for 256 levels of gray 24 bits for colors (8 bits for each component) How can we know if a sequence of bits corresponds to 24 black and white or only 1 pixel in color? How can we know if the image is rectangular or square? A header is needed to specifiy the pixels coding and the image dimension

Bitmap or vector images? The computer doesn’t know the content of an image In order to know there is a disc, a pattern recognition algorithm is required How to better code such images? It would be easier to describe the disc And a lot more succinct! Good for technical drawings, but not for pictures! A vector image is a set of mathematical shapes with their colors

Sound coding Signal composed of an infinity of intermediate values We can’t code them all! Some approximate values Close enough so that human ear can’t hear the difference A set of bits for each value With a header to specify the frequency Sampling Nom abrégé de cours - Enseignant

"Vector" coding of sound A piece of music is also a score Easy to code in bits And instruments characteristics Type, timbre, … Similar coding to that of the vector images Fichiers MIDI Nom abrégé de cours - Enseignant

To remember Image and sound can be coded by sequences of numbers, of bits A program enables the computer to interpret this coding to display or to print an image, to play a sound, … … and to code data during an image scan, a sound recording, … Between both (storage on the disc, transfer on the Internet, pictures manipulation), the data can remain coded

Illustrations p.2 : Six Fingers © Inria - J.C. Moschetti