Understanding types of media

Table of Contents | Electrifier Overview

What is Electrifier Pro? | Understanding the Interface | Understanding Multimedia Authoring | Understanding Movies, Actors, and Sprite Tracks

Understanding types of media

Familiarity with the various forms of computer media--vector graphics, bitmap graphics, digitized video, digitized audio, and synthesized music--is important when designing a fast yet compelling web site.

Media storage

All computer media--vector graphics, bitmap graphics, digitized video, digitized audio, and synthesized music--are ultimately converted into pixels (in the case of graphics) and sound samples (in the case of audio) when they are played back. However, the way data is stored in a file makes a profound difference in the way in which it plays back and to the speed with which the file will download.

Some types of media, such as bitmap graphics, digitized audio, and video, essentially store the same series of pixels or sound samples that will be played back; other media such as vector graphics, synthesized music, and 3D, store a series of instructions for generating the sound samples or image pixels, rather than the pixels themselves. These latter types of media are typically smaller in file size, but place more demands on the viewer's computer.

Vector graphics: Vector graphics such as Illustrator®, or Freehand® files describe an image by a set of of mathematically-defined lines and curves, rather than the pixels (spots of color) used in bitmap graphics. For example, a red circle would be described as a circular curve, the color red, and its location. The computer reads these descriptions and uses them as instructions to draw a new graphic.

Vector graphics are well suited for the web since they are small in file size and produce high-quality, full-screen images. Vector graphics can be used for animations which require scaling effects such as the zoom effect.

Since vector graphics are not pixel-based, they are scalable to any size while retaining superior image quality and small file size. If the image is resized, moved, or rotated, the program simply updates the drawing instructions, and does not need to include a new version of the image.
Bitmap graphics: Bitmap or raster images such as Photoshop® or GIF(SM) files describe an image by a rectangular grid of pixels (spots of color). For example, a red circle would be described by a group of pixels, each with a given location and color representing the circle and its rectangular background. The computer reads this list of pixels and draws them on the screen, reproducing the original image.

Bitmap images are most frequently used for photographs or paintings. On the web, they are well suited for detailed images which are difficult to represent as vector graphics.

Since every pixel must be stored in the file, sizes for bitmap image files can become quite large (1.2 MB for a 640x480 image); as a result, many formats use compression to make the files smaller. Because they are composed of a finite number of pixels, bitmap images will appear jagged if scaled to a larger size.
Digitized video: Digitized video such as MPEG, AVI, or QuickTime movie files describe a video by a series of bitmap images--often called frames--taken many times a second. For example, a video of a dancer would be made up of a series of pictures of the person, taken at regular intervals during the dance. The computer reads the frames in the video and draws them in sequence, reproducing the original moving image.

Digitized video is used for viewing video with a computer, whether on the web, on a hard disk, or on CD-ROM or DVD.

Since every pixel of every frame must be stored in the file, sizes for digitized video files can become very large (1 to 30 MB per second of full-screen video); as a result, most formats use compression to make the files smaller.
Digitized audio: igitized audio such as AIFF or Wave files describe a sound by a series of amplitude (volume) measurements--often called samples--taken many thousands of times per second. The way the sample values change with time defines sound characteristics such as pitch, volume, and timbre.
For example, a recording of a person speaking would include a series of samples recorded at regular intervals as they spoke; a recording of an a acapella vocal group would have the same format, but the samples would be more varied. The computer reads the samples, and plays them over the speakers in sequence, reproducing the original sound.

Digitized sound is most frequently used for high quality audio such as speech or music.

Since every sound sample must be stored in the file, sizes for digitized sound files can become quite large (200 K per second of CD-quality audio); as a result, many formats use compression to make the files smaller.
Synthesized music: Synthesized music files such as MIDI or MOD files describe a piece of music by a set of playing instructions. Characteristics can include pitch, note timing, voice (instrument), attack speed, and other common synthesizer settings. For example, a trumpet solo would be described by the name of the instrument and a series of notes and rests; a trumpet concerto would be described in the same manner, but it would include descriptions of all the other instruments' parts as well. The computer reads the descriptions of the notes and uses them as instructions to play the tune, using QuickTime's built-in instruments (or a synthesizer).

On the web, synthesized music is well suited to musical accompaniment for a page or in situations where small file sizes are critical.

Since synthesized music only contains playing instructions, file sizes are very small, but the file cannot represent non-instrumental information such as hall acoustics, individual instrument timbre, or vocal music.
Virtual Reality: Virtual Reality (VR) movies such as QuickTime VR objects and panoramas describe a 360 degree view of an object or location by a series of bitmap images taken at many different angles. These images are then combined--or "stitched"--into a single image which can be viewed as if the viewer were inside the picture. For example, a VR panorama of a museum exhibit would include a sequence of photographs of the various exhibits, combined into a single 360 degree image of each room. The computer reads the pieces of the image and plays them in sequence as the VR is panned, distorting the pieces at the edges to make the scene flow by realistically.

Virtual Reality is used to present immersive virtual environments and three-dimensional objects. It is most frequently used on CD-ROM due to its large file sizes, but can also be used on the web with QuickTime 3.

Since every pixel of the combined panorama is stored in the file, VR file sizes can be very high, just like video files; as a result, most VR movies use compression to make the files smaller.
3-D: 3D graphics such as 3DMF files describe a three-dimensional object by a set of mathematically defined surfaces like a flexible sheet covering the object. They are similar to vector graphics in that both use mathematical objects to represent the graphic rather than being tied to a particular size. For example, a cube would be described by its 8 corner points; a globe would be described in a similar manner, but it might include all the points where the lines of latitude and longitude cross.

3D graphics are used to present three-dimensional objects and environments that can be navigated interactively and viewed from any angle. It is most frequently used for games, but is gaining popularity on the web.

Since 3D graphics are not pixel-based, they can be zoomed and rotated in 3D space without loss of quality. Because they only describe the structure of the object, they are usually much smaller in file size than equivalent VR objects.

What is Electrifier Pro? | Understanding the Interface | Understanding Multimedia Authoring | Understanding Movies, Actors, and Sprite Tracks