Multimedia Data: Input, Format, and Storage, Lecture notes of IP Multimedia Subsystems

Download Multimedia Data: Input, Format, and Storage and more Lecture notes IP Multimedia Subsystems in PDF only on Docsity! 1 A Brief Look at Multimedia Data: Input and Format Text and Static Data • Source: keyboard, speech input, optical character recognition, data stored on disk. • Stored and input character by character: – Storage of text is 1 byte per character (text or format character). – For other forms of data (e.g. Spreadsheet files). May store format as text (with formatting) others may use binary encoding. • Format: Raw text or formatted text e.g HTML, Rich Text Format (RTF), Word or a program language source (C, Pascal, etc.. B. Okuku 2 •Not temporal — BUT may have natural implied sequence e.g. HTML format sequence, Sequence of C program statements. • Size Not significant w.r.t. other Multimedia data. B. Okuku 5 Audio • Audio signals are continuous analog signals. • Input: microphones and then digitised and stored • CD Quality Audio requires 16-bit sampling at 44.1 KHz •Even higher audiophile rates (e.g. 24-bit, 96 KHz) • 1 Minute of Mono CD quality (uncompressed) audio requires 5 Mb. • 1 Minute of Stereo CD quality (uncompressed) audio requires 10 Mb. • Usually compressed (E.g. MP3, AAC, Flac, Ogg Vorbis). B. Okuku 6 Video • Input: Analog Video is usually captured by a video camera and then digitised. • There are a variety of video (analog and digital) formats • Raw video can be regarded as being a series of single images. There are typically 25, 30 or 50 frames per second. • E.g. A 512 512 size monochrome video images take 25 0:25 = 6.25Mb for a minute to store uncompressed. • Typical PAL digital video (720 576 pixels per colour frame) 1:2 25 = 30Mb for a minute to store uncompressed. • High Definition DVD (14401080 = 1.5 Megapixels per frame) 4:5 25 = 112.5Mb for a minute to store uncompressed. (There are higher possible frame rates!) • Digital video clearly needs to be compressed for most times. B. Okuku