CS3352 - ANNA UNIVERSITY - MULTIMEDIA AND ANIMATION UNIT II

CS3352

1. UNIT II - MULTIMEDIA FILE FORMATS AND STANDARDS File formats – Text, Image file formats, Graphic and animation file formats, Digital audio and Video file formats, Color in image and video, Color Models. Multimedia data and file formats for the web.

2. File Formats for multimedia The following is an outline of current file formats used for the production and delivery of multimedia data. Text Formats RTF Rich Text Format is the primary file format introduced in 1987 by Microsoft with the specification of their published products and for cross-platform documents interchange. Plain text Plain text files can be opened, read, and edited with most text editors. commonly used are Notepad (Windows), Gedit or nano ( Unix, Linux), TextEdit (Mac OS and so on. Other computer programs are also capable of reading and importing plain text . Plain text is the original and popular way of conveying an e-mail.

3. Image Formats

4. TIFF ( Tagged Image File Format) This format is common in desktop publishing world (high quality output), and is supported by almost all software packages. Recent versions of TIFF allows image compression, and the format is comfortable for moving large files between computers. BMP (Bitmap) Initially this format is in use with Windows 3.1. It is quite large and uncompressed and hence BMP is used for the highresolution or large images. DIB (Device Independent Bitmap) This format which is similar to BMP, allows the files to be displayed on a variety of devices.

5. GIF (Graphics Interchange Format) GIF is a compressed image format. Most of the computer color images and backgrounds are GIF files. This file format is best suitable for graphics that uses only limited colors , and it is the most popular format used for online color photos. 13-bit Color look up table is used by the GIF format to identify its color values. This format is supported widely. JPEG (Joint Photographic Experts Group) JPEG was designed to attain maximum image compression. It uses lossy compression technique, where a compression method is referred that loses some of the data required for the image reconstruction. works good with photographs, naturalistic artwork, and similar material but functions less on lettering, live drawings or simple cartoons. TGA ( Tagra ) It is the first popular format for high-resolution images. TGA is supported by Most of the video-capture boards.

6. PNG (Portable Network Graphics) An extensible file format for the less-loss, portable and well-compressed storage of raster images. PNG acts as a replacement for GIF and also replaces multiple common uses of TIFF. PNG works well with online viewing applications like Worldwide Web . so it is fully streamable with a best display option.

7. Digital Audio File Formats Besides the variety of audio file formats available, the most common formats are wave files (.WAV) and MPEG Layer-3 files (.MP3), WMA and RA.

8. WAV:  This is an uncompressed audio format developed by Microsoft and IBM. WAV documents include raw, lossless PCM (Pulse Code Modulation) audio statistics—high audio incredible but huge record sizes. MP3:  MP3 is the most famous compressed audio layout. uses lossy ” compression, doing away with inaudible sounds to reduce the file duration significantly while maintaining brilliant audio Widely supported. FLAC (Free Lossless Audio Codec) It also losslessly compresses audio records without dropping the first-rate; however, the documents are larger than MP3s. Used wherein better pleasantness is preferred. WMA (Windows Media Audio) Compressed audio layout was advanced via Microsoft as an alternative to MP3. Contains DRM duplicate protection capabilities.

9. AAC (Advanced Audio Coding ) A standardized and improved version of MP3 Used through Apple’s iTunes shop. Can produce more wonderful than MP3 at comparable bit expenses. AIFF (Audio Interchange File Format) An uncompressed audio layout is superior to the useful resources of Apple. Contains first-rate audio. Ogg Vorbis is a free, open-source compressed audio format. Alternative to MP3 and AAC. MIDI:  Stores virtual sheet music facts in preference to audio waveforms. Used for virtual music and computer-generated songs.

10. Digital Video File Formats

11. AVI (Audio/Video Interleave ) AVI is the video file format for Windows. Here sound and picture elements are stored in alternate interleaved chunks in the file. MPEG (Moving Picture Experts Group) MPEG is a standard for generating digital video and audio compression under the International Standards Organization (ISO ) by a group of people. The group has developed MPEG-1, the standard on which Video CDs and MP3 are based, MPEG-2 , the standard that supports products such as Digital Television set-top boxes and DVDs, MPEG-4, the standard for multimedia and mobile web.MPEG-7, the standard for the search of audio and visual content. Research on MPEG-21 “Multimedia Framework” has started in 2000. Simply MPEG is the standard for digital video and audio compression.

12. MOV :  It was developed by Apple for its own ecosystem. It is commonly used with QuickTime. It supports various codecs and is used for multimedia projects. It is primarily used by video editors because it provides the highest quality for editing It can store multiple tracks, text files, and effects. It is used for multimedia projects, video editing, and distribution of content for the Apple platform . Its only downside is its poor compatibility with other devices.

13. 3GP :  It is the Multimedia container format that is commonly used for mobile phones. It is used where lower video quality is a problem and the only focus is to get a small file size. WMV :  It is a video compression format developed by Microsoft. It is popular for its small file size while maintaining reasonable video quality. It lacks compatibility with certain operating system. It is suitable for online streaming and playback on Windows Media Player. It is compatible with Windows based applications. Its benefit is that files can be sent through e-mail . It is used where lower video quality is not a problem and the only focus is to get a small file size. It isn’t compatible with Apple devices.

14. Color in Image and Video Color is a vital component of multimedia. Management of color is both a subjective and a technical exercise. Picking the right colors and combinations of colors for your project can involve many tries until you feel the result is right . Understanding Natural Light and Color The letters of the mnemonic ROY G. BIV, learned by many of us to remember the colors of the rainbow, are the ascending frequencies of the visible light spectrum: red, orange, yellow, green, blue, indigo, and violet. Ultraviolet light, on the other hand , is beyond the higher end of the visible spectrum and can be damaging to humans.

15. The color white is a noisy mixture of all the color frequencies in the visible spectrum. The cornea of the eye acts as a lens to focus light rays onto the retina. The light rays stimulate many thousands of specialized nerves called rods and cones that cover the surface of the retina. The eye can differentiate among millions of colors , or hues, consisting of a combination of red , green, and blue. Additive Color : In the additive color model, a color is created by combining colored light sources in three primary colors : red, green, and blue (RGB). This is the process used for a TV or computer monitor

16. Subtractive Color : In the subtractive color method, a new color is created by combining colored media such as paints or ink that absorb (or subtract) some parts of the color spectrum of light and reflect the others to the eye. Subtractive color is the process used to create color in printing. The printed page is made up of tiny halftone dots of three primary colors , cyan, magenta , and yellow (CMY).

17. Basics of Color Light and Spectra • Visible light is an electromagnetic wave in the 400 nm - 700 nm range. Most light we see is not one wavelength, it's a combination of many wavelengths.

18. The profile above is called a spectral power distribution or spectrum. The Human Retina The eye is basically just a camera Each neuron is either a rod or a cone. Rods are not sensitive to color . Cones and Perception Cones come in 3 types: red, green and blue. Each responds differently to various frequencies of light. The following figure shows the spectral sensitivity functions of the cones and the luminous-efficiency function of the human eye.

19. The color signal to the brain comes from the response of the 3 cones to the spectra being observed. That is, the signal consists of 3 numbers:

20. where E is the light (spectral power distribution) and S are the spectral sensitivity functions. A color can be specified as the sum of three colors . So colors form a 3 dimensional vector space. The following figure shows the amounts of three primaries needed to match all the wavelengths of the visible spectrum. The negative value indicates that some colors cannot be exactly produced by adding up the primaries.

21. CIE Chromaticity Diagram Q : Does a set of primaries exist that span the space with only positive coefficients ? A: Yes, but no pure colors . In 1931, the CIE (Commission Internationale de L'Eclairage , or International Commission on Illumination) defined three standard primaries (X, Y, Z). The Y primary was intentionally chosen to be identical to the luminous-efficiency function of human eyes.

22. The edges represent the "pure" colors (sine waves at the appropriate frequency) White (a blackbody radiating at 6447 kelvin ) is at the "dot" When added, any two colors (points on the CIE diagram) produce a point on the line between them .

23. Color Models A color image is a 2-D array of (R,G,B) integer triplets. These triplets encode how much the corresponding phosphor should be excited in devices such as a monitor. RGB Color Model for CRT Displays CRT displays have three phosphors (RGB) which produce a combination of wavelengths when excited with electrons .

24. CMY Color Model Cyan, Magenta, and Yellow (CMY) are complementary colors of RGB. They can be used as Subtractive Primaries . CMY model is mostly used in printing devices where the color pigments on the paper absorb certain colors ( e.g .,no red light reflected from cyan ink).

25. The gamut of colors is all colors that can be reproduced using the three primaries The Lab gamut covers all colors in visible spectrum The RGB gamut is smaller, hence certain visible colors (e.g. pure yellow, pure cyan) cannot be seen on monitors The CMYK gamut is the smallest (but not a straight subset of the RGB gamut)

26. Color Models in Video YIQ and YUV are the two commonly used color models in video YUV Color Model Initially , for PAL analog video, it is now also used in CCIR 601 standard for digital video Y ( luminance) is the CIE Y primary. Y = 0.299R + 0.587G + 0.114B Chrominance is defined as the difference between a color and a reference white at the same luminance. It can be represented by U and V -- the color differences. U = B - Y V = R - Y If b/w image, then U = V = 0. --> No chrominance! ** In actual PAL implementation: U = 0.492 (B - Y) V = 0.877 (R - Y)

27. Sample YUV Decomposition