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  • 1. 4. Digital Media After this lecture, you should be able to: •Describe the advantages, disadvantages, and uses for digital media •List the equipment and software that can be used to work with various types of digital media •Identify digital media files by their filename extensions •Understand the advantages and disadvantages of using each type of digital media on the web •Explain how resolution, image size, color depth, and color palettes can be manipulated to adjust the file size of a bitmap graphic •Describe the procedures required to convert bitmap graphics into vectors, and vector graphics into bitmaps •Explain how wireframes, rendering, and ray tracing apply to 3-D graphics •Define the differences between 3-D animation and desktop video •Describe how to shoot, capture, edit, and process desktop video •Explain how window size, frame rate, and compression affect the file size for a desktop video •Describe the process of creating an MP3 music file 4.1 Bitmap Graphics •Bitmap graphic – “raster graphic”, consists of a grid of dots, and the color of each dot is stored as a binary number •Typically used to create realistic images •Cartoons in video games •3-D graphics software •Digital cameras •E-mail photos •Paint software – graphics software for creating bitmap graphics •Adobe Photoshop •Jasc Paint Shop Pro •Microsoft Paint •Scanner – converts printed pages and images into a bitmap graphic •Divides image into fine grid of cells, and assigns a digital value for the color of each cell •Values are transferred to your computer’s disk and stored as a bitmap •Digital camera – digitizes real objects •Takes photo in digital format, which you can then transfer directly to your computer •Some digital cameras store images on floppy disks, CDs, mini-CDs, or miniature hard disk drives •Flash memory – popular technology for digital camera memory modules •Holds data without consuming power •Media transfer – remove the media from your camera and insert it into the appropriate drive of your computer •Direct cable transfer – Fire Wire ports are used to transfer data
  • 2. •Infrared port – cameras “beam” the data to computer’s infrared port •Memory card readers – small device connected to computer and designed to read flash cards •Floppy disk adapters – adapter shaped like a floppy with slot for a flash memory module •You can use graphics software to modify or edit bitmap graphics by changing individual pixels •Retouch, Repair, Remove red eye or erase “rabbit ears” •Bitmap graphics require large amounts of storage, and take long time to load •Resolution – dimensions of the grid that forms a bitmap graphic •Number of horizontal and vertical pixels that it contains •150 x 100 – 150 pixels across and 100 pixels high •High-resolution graphics contain more data than low-resolution •Better printouts •Megapixels – total number of pixels in a graphic •Each pixel is stored as one or more bits •More pixels means larger file size •Bitmap has no fixed physical size •Size depends on density •Graphic retains same resolution no matter how much you stretch or shrink the graphics physical size •Most graphics software lets you specify the size at which image is printed without changing the resolution of the bitmap graphic •Get better printout if an image meets or exceeds the printers dpi (dots per inch) •Typically, one pixel corresponds to one pixel on the screen •If image is larger than screen, you will have to scroll •Cropping – process of selecting part of an image •Resolution dependent – quality of the image depends on its resolution •Can reduce image quality •If you attempt to enlarge a bitmap, computer must add pixels •Pixel interpolation – creates new pixels by averages the colors of nearby pixels •Pixelated – undesirable bitmappy appearance •Color depth – is the number of colors that are available for use in an image •Larger number, better quality and larger file size •Monochrome bitmap – pixel could be “on” or “off” •On – represented by a 1 bit •Off – represented by a 0 bit •Each row of the bitmap stored as 0s and 1s •Size of file given by resolution in case of monochrome bitmaps •Requires very little storage •True color bitmap (24-bit bitmap) – 16.7 million colors •Each pixel requires 3 bytes of storage •Color based on intensity levels or red, green, blue •8-bits red, 8-bits green, 8-bits blue (24-bits) •32-bit bitmap – 16.7 million colors plus special effects
  • 3. •Reducing color depth can reduce size of file •To reduce color depth, manipulate color palette •Color palette – digital version of artist’s palette that holds the selection of colors for use •256 colors – eight bits per pixel (1/3 size required for true color bitmap) •Use color palette or color picker tool •Grayscale palette – displays an image using shades of gray (usually 256 shades of gray) •System palette – selection of colors used by the operating system •Windows has 20 permanent colors and 236 that can be changed •Web palette – standard set of colors used by the Internet Web browsers •Dithering – uses patterns composed of two or more colors to produce the illusion of additional colors and shading, relying on the human eye to blend colors and shapes •Bitmap graphics that you wish to print should remain in True Color format •Those sent in e-mail or posted on Web site should be reduced to 256-color palette •BMP – native bitmap graphic file format of Microsoft Windows OS •PCX – one of original personal computer bitmap graphics file formats (8-bit – 256 color) •TIFF (Tag Image File Format) – highly flexible and platform-independent graphics file format •Supports True Color •Used by scanners and digital cameras •JPEG – graphics format with built-in compression •You control level of compression •Uses True Color •GIF – limited to 256 colors •PNG – 48-bit True Color, compresses without losing data •Public domain format •Selecting the best graphics file format to use depends on what you intend to do with the image •Scanned and digital images – could be stored as JPEG or TIFF format •Images for web pages – GIF or JPEG format •Designing Windows controls – BMP format 4.2 Vector and 3-D Graphics •Vector graphic – consists of set of instructions for re-creating a picture •Instead of storing the color value for each pixel, a vector graphic file contains the instructions that the computer needs to create the shape, size, position, and color for each object in an image •Flat, cartoon-like quality •Filename extension •.wmf, .dxt, .mgx, .eps, .pict, .cgm •Vectors resize better than bitmaps •Vector images usually require less storage space than bitmaps
  • 4. •It is easier to edit an object in a vector graphic than an object in bitmap graphic •Vector graphics tend not to produce images that are as realistic as bitmap images •Digitizing tablet – device that provides a flat surface for a paper-based drawing •Drawing software – vector graphics software •Helps you easily edit individual objects by changing their sizes, shapes, positions or colors •Gradient – smooth blending of shades from one color to another, or from light to dark •Metafiles – graphics that contain both bitmap and vector data •Apply bitmap texture to vector graphic •Rasterization – works by superimposing a grid over a vector image, and determining the color for each pixel •Once converted, the resulting graphic no longer has the qualities of a vector graphic •Tracing software – locates the edges of objects in a bitmap image and converts the resulting shapes into vector graphics objects •Browsers support a limited number of graphics formats – Gif and Jpeg •Support for vector graphics has been slow, but plug-ins and players are currently available •SVG (Scalable Vector Graphics) – designed for the Web •Automatically resized when displayed on different screens •Uses <EMBED> tag •Flash graphics – can be static or animated and require less space than SVG graphics, but require a browser plug-in to be viewed •Vector graphics appear with same consistent quality on all computer screens •Any text contained in a vector image is stored as actual text, not just a series of colored dots •Vector graphics on the Web have compact file sizes •3-D graphics – stored as a set of instructions •Wireframe – framework for a 3-D graphic •Rendering – process of covering a wireframe with surface color and texture •Ray tracing – technique for adding light and shadows to a 3-D image •3-D graphics software •AutoCad, Caligari truSpace •High-end workstations •1 GHz Pentium or Macintosh G3 or better •High-resolution monitor •Graphics card with 128 MB of memory •3-D graphics can be animated to produce special effects for movies, or create interactive, animated characters and environments for 3-D computer games •Pixar Animation Studios •DreamWorks •Special effects can be created and incorporated into final footage •3-D computer game animation happens in “real-time” •Can be created on a standard PC or iMac using commercially available software
  • 5. •Commonly expensive and have a steep learning curve •Shareware programs are available •3-D Graphics InfoWeb 4.3 Desktop Video •Desktop video – videos that are constructed and played using a personal computer •Stored on hard disks, CDs, DVDs, videotapes, or the Web •Not quite like standard of DVD movies, but suitable for variety of personal and professional uses •Video is composed of a series of frames •Each frame is essentially a still picture (can be stored as bitmap graphic) •Frame rate – number of frames per second •Feature films – 24 fps (frames per second) •Desktop video – 15 fps •Most computers equipped for viewing videos; however, video playback quality can vary Depending on Microprocessor, RAM capacity, and Capabilities of graphic card •For web, Internet connection speed is also issue •For Internet also need •Player – Quicktime, Windows MediaPlayer •Several file formats are popular for desktop videos •AVI, QuickTime, MPEG, RealMedia, ASF •The basic process consists of following steps •Shoot the video footage •Transfer the footage to your computer’s hard disk •Edit the video and soundtrack •Output the video in its final format by selecting frame rate, window size, file format, and compression levels •You can use analog or digital video camera to shoot footage •Digital video camera – stores footage as a series of bits •Analog video camera – normal video camera •Video signal stored as continuous track of magnetic patterns •Must be digitized •Videoconferencing cameras – attach directly to a computer •Captures video data in digital format which can then be directly transferred to a computer for editing •Produce higher quality video than analog or videoconferencing cameras •Images tend to be sharper and more colorful •Higher quality of original video, the better the final video will look •When processed and stored, some of image data is eliminated to reduce the video file to a manageable size •To produce good quality video •Use a tripod to maintain a steady image •Move the camera slowly •Zoom in and out slowly
  • 6. •Direct your subjects to move slowly •Position your shot well •Ask the subjects of your video to wear solid colored clothing •In order to digitally edit, process, and store a desktop video, you must transfer the video footage from your camera to your computer •Basic method for transferring video footage is to send the data over a cable that connects your camera to your computer •Equipment depends on your camera and your computer •Video capture device – converts analog camera signal into digital data •Video capture software – allows you to start and stop the transfer, and select the display size, frame rate, filename, and file format for your video footage •Linear editing – recording segments from one videotape onto another tape •Non-linear editing – requires a computer hard disk and video editing software •Can use random access devices to easily edit and arrange footage •Video editing software – lets you edit video into final desktop video •After editing, video editing software combines data from all of the video and audio files that you selected into a single file as a desktop video •Select file format, QuickTime or AVI • A full-screen True Color image at 1,024x768 resolution requires 2,359,296 bytes; with 24 fps, requires 56,623,104 bytes •10 minutes requires almost 34 GB of storage space •To shrink, decrease size of window, number of frames, and select a compression technique •To reduce size •Decrease the size of the video window •Reduce the frame rate •Compress the video data •Codec (compressor/decompressor) – software that compresses a file when a desktop video is created and decompresses the file when video is played •MPEG, Indeo, Cinepak, DivX, Video 1 •The ultimate goal is to store a high-quality video image in a small file •Difficult to predict the result of compression •Codec used to compress must be used to decompress the video when it is played •Missing codecs account for high proportion of desktop video glitches •Streaming video – sends small segment of the video to your computer and begins to play it •Web server sends next part of the file to your computer, and so on, until the video ends •Two styles •External video – displays a link to a video file •<A HREF = “ducks.avi> 1.5 MB AVI Video </A> •Internal video (inline video) – uses EMBED tag, “in-place video” •<EMBED SRC=“ducks.avi width=145 height=60> •Dial-up connections are slow •Typical 56 Kbps connection reach speeds of only 44 Kbps
  • 7. •Video to play At 15 fps, with 256 colors, 357 bytes per frame; playing in a window of 15 by 11 pixels (1/6 of an inch wide) •High-speed Internet connections provide much more bandwidth for streaming video •Most Web sites provide one video file that’s optimized for dial-up and one optimized for high-speed (DSL, cable, and ISDN connections) 4.4 Digital Sound •Waveform audio is a digital representation of sound. •Music, voice, and sound effects can all be recorded as waveforms •Sampling rate – refers to number of times per second that a sound is measured during the recording process •Expressed in hertz (Hz) •Audio CDs have sampling rate of 44.1 KHz •Stereo effects, requires 32 bits of storage space for each sample •Floppy, stores only eight seconds of music •45 minutes of music – 475 MB •To conserve space, reduce sampling rate •Sound card – contains a variety of input and output jacks, plus audio- processing circuitry •Plugs into a PCI expansion slot inside the system unit •Digital signal processor – performs three important tasks •Transforms digital bits into analog waves •Transforms analog waves into digital bits •Handles compression and decompression, if necessary •Recognize a waveform audio file by its extension •Wave (.wav) – created by Windows •Audio Interchange Format (.aif) – created by Apple •RealAudio (.ra) – proprietary format created by RealNetworks •MP3 (.mp3) – MPEG format, popularized by a free music exchange service called Napster •Audio software comes in many flavors •To play, you must use an audio player •Microsoft Media Player •To record, you may need another software component •Microsoft Sound Recorder software •Software may be part of your operating system or purchased separately •Yes, files can be embedded using HTML •<EMBED SRC = “daisy.wav”> or <BGSOUND = “imagine.wav”> •Streaming format to avoid lengthy delays •MP3 is a compressed waveform audio format that stores digitized music, vocals, and narration in such a way that the sound quality is good, but file size remains relatively small •CD ripper – grabs tracks from audio CD •MP3 encoder – converts Wave file into MP3 format
  • 8. •MP3 files can be stored anywhere or relocated to a portable MP3 player •Synthesized sound – artificially created sound •MIDI or synthesized speech •MIDI (Musical Instrument Digital Interface) – specifies standard way to store music data •MIDI sequence – encoded music stored as .mid, .cmf, or .rol •Most sound cards are equipped to capture data from a MIDI instrument •Wavetable – set of pre-recorded musical instrument sounds •MIDI is a good choice for adding background music to multimedia projects and Web pages •<EMBED SRC = “sousa.mid”> •Embed tags are placed within an HTML document •MIDI software can be used to compose your own tunes or get permission to use MIDI file that you find on the Web •Speech synthesis – process by which machines produce sound that resembles spoken words •Speech recognition (or “voice recognition”) – ability of machine to “understand” spoken words •Phonemes – basic sound units strung together by speech synthesizers •Text-to-speech software – generates sounds that are played through your computer’s standard sound card •Speech synthesis is a key technology in wireless communication •Speech recognition software – analyzes the sounds of your voice and converts them to phonemes •Next, the software analyzes the content of your speech; it compares the phonemes to the words in a digital dictionary •Speech recognition software can be integrated with word processing software so that you can enter text by speaking into a microphone •Windows XP includes speech recognition software

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