Wednesday, April 22, 2009

Introduction to the Internet: Multimedia terms

AVI [Video for Windows]
Short for Audio Video Interleave, the file format for Microsoft’s Video for Windows standard. A format developed by Microsoft Corporation for storing video and audio information. Files in this format have a .AVI extension. AVI files are limited to 320 x 240 resolution, and 30 frames per second, neither of which is adequate for full-screen, full-motion video. However, Video for Windows does not require any special hardware, making it the lowest common dominator for multimedia applications. Many multimedia producers use this format because it allows them to sell their products to the largest base of users.

Video for Windows supports several data compression techniques, including RLE, Indeo, and Cinepak. A competing software-only video format is Quicktime.

Pronounced jiff or giff (hard g) stands for graphic interchange format, a bit-mapped graphics file format used by the World Wide Web, CompuServe, and many BBSs. GIF supports color and various resolutions. It also includes data compression, making it especially effective for scanned photos.

Short for Joint Photographic Experts Group, and pronounced jay-peg, JPEG is a lossy compression technique for color images. Although it can reduce file sizes to about 5% of their normal size, some detail is lost in the compression.

Pronounced middy, an acronym for musical instrument digital interface, a standard adopted by the electronic music industry for controlling devices, such as synthesizers and sound cards, that emit music. At minimum, a MIDI representation of a sound includes values for the note’s pitch, length, and volume. It can also include additional characteristics, such as attack and delay time.

Short for Moving Pictures Expert Group, and pronounced m-peg, a working group of ISO. The term also refers to the family of digital video compression standards and file formats developed by the group. MPEG generally produces better-quality video than competing formats, such as Video for Windows, Indeo, and QuickTime. MPEG files can be decoded by special hardware or software.

The use of computers to present text, graphics, video, animation, and sound in an integrated way. Long touted as the future revolution in computing, multimedia applications were, until the mid-90s, uncommon due to the expensive hardware required. With increases in performance and decreases in price, however, multimedia is now commonplace. Nearly all PCs are capable of displaying video, though the resolution available depends on the power of the computer’s video adapter and CPU.

Is the file extension for MPEG, audio layer 3. Layer 3 is one of three coding schemes (layer 1, layer 2, layer 3) for the compression of audio signals. Layer 3 uses perceptual audio coding and psychoacoustic compression to remove all superfluous information (more specifically, the redundant and irrelevant parts of a sound signal. The stuff the human ear doesn’t hear anyway). It also adds a MDCT (Modified Discrete Cosine Transform) that implements a filter bank, increasing the frequency resolution 18 times higher than that of layer 2.

Because MP3 files are small, they can easily be transferred across the Internet. Controversy arises when copyrighted songs are sold and distributed illegally off of Web Sites. On the other hand, musicians may be able to use this technology to distribute their own songs from their own Web sites to their listeners, thus eliminating the need for record companies. Costs to the consumer would decrease, and profits for the musicians would increase.

A video and animation system developed by Apple Computer. QuickTime is built into the Macintosh operating system and is used by most Mac applications that include video or animation. PCs can also run files in QuickTime format, but they require a QuickTime driver. QuickTime supports most encoding formats, including AVI and ActiveMovie.

The de facto standard for streaming audio data over the World Wide Web. RealAudio was developed by RealNetworks and supports FM-stereo-quality sound. To hear a Web page that includes a RealAudio sound file, you need a RealAudio player or plug-in, a program that is freely available from a number of other places. It was included in current (2003) versions of both Netscape Navigator and Microsoft Internet Explorer.

Sound card
An expansion board that enables a computer to manipulate and output sounds. Sound cards are necessary for nearly all CD-ROMs and have become commonplace on modern personal computers. Sound cards enable the computer to output sound through speakers connected to the board, to record sound input from a microphone connected to the computer, and manipulate sound stored on a disk.

Nearly all sound cards support MIDI, a standard for representing music electronically. In addition, most sound cards are Sound Blaster-compatible, which means that they can process commands written for a Sound Blaster card, the de factor standard for PC sound.

A technique for transferring data such that it can be processed as a steady and continuous stream. Streaming technologies are becoming increasingly important with the growth of the Internet because most users do not have fast enough access to download large multimedia files quickly.

With streaming, the client browser or plug-in can start displaying the data before the entire file has been transmitted. For streaming to work, the client side receiving the data must be able to collect the data and send it as a steady stream to the application that is processing the data and converting it to sound or pictures. This means that if the streaming client receives the data more quickly than required, it needs to save the excess data in a buffer. If the data doesn’t come quickly enough, however, the presentation of the data will not be smooth.

There are a number of competing streaming technologies emerging. For audio data on the Internet, the de facto standard is Progressive Network’s RealAudio.

The format for storing sound in files developed jointly by Microsoft and IBM. Support for WAV was built into Windows 95 making it the de facto standard for sound on PCs. WAV sound files end with a .wav extension and can be played by nearly all Windows applications that support sound.
All definitions taken from Webopedia

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