MIS 315 - Bsharah

Digital Media Handout

Digital Media Handout

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Contents

• Section A: Digital Sound

• Section B: Bitmap Graphics

• Section C: Vector and 3-D Graphics

• Section D: Digital Video

• Section E: Digital Rights Management

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Section A: Digital Sound

• Digital Audio Basics

• Portable Audio Players

• MIDI Music

• Speech Recognition and Synthesis

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What is Digital Audio?

• Digital representation of sound.

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Digital Audio Basics

• Sampling rate refers to number of times per second that a sound is measured.

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Digital Audio Basics

• Sound cards are responsible for transforming bits stored in an audio file into music, sound effects, and narrations.– Digital signal processor.

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Waveform Audio

• The most popular waveform audio formats include AAC, AIFF, MP3, RealAudio, Wave, and WMA.– See Page 424 for file formats advantages and

disadvantages.

• Audio or media player software allows you to record and play waveform audio files.

• You can embed waveform files into a Web page.

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Portable Audio Players

• Pocket-sized, battery-powered device that stores digital music.– Zune

• Digital music is available from a wide variety of sources.– Formats include MP3, AAC,

and WMA

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Musical Instrument Digital Interface (MIDI) Music

• MIDI specifies a standard way to store music data for synthesizers, electronic MIDI instruments, and computers.

• MIDI-capable sound cards contain a wavetable.– Set of prerecorded musical instrument sounds.

• Does not produce high-quality vocals.

• Does not have full resonance of “real” sound or that of waveform audio.

• Useful for adding background music to a web page/multimedia project.

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MIDI Music

• Music composition software provides tools for entering notes, specifying instruments, printing sheet music, and saving compositions in formats such as MIDI.

• The computer encodes the music as a MIDI Sequence.

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Speech Recognition and Synthesis

• Speech synthesis is the process by which machines produce sound resembling spoken words.– Text-to-speech software.– Strings together basic sound units, called phonemes, to form

words.

• Speech recognition refers to the ability of a machine to understand spoken words.– Speech recognition software.– Uses sound card to transform analog waves to digital, then

maps sounds to phonemes and compares phoneme groups to words in digital sound dictionary.

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Section B: Bitmap Graphics

• Bitmap Basics

• Scanners and Cameras

• Image Resolution

• Color Depth and Palettes

• Image Compression

• Bitmap Graphics Formats

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Bitmap Graphics (aka Raster Graphic)

• Composed of a grid of dots where the color of each dot is stored as a binary number.

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Scanners or Cameras Can Be Used To Create Bitmap Images

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Scanners and Cameras

• Graphics software is used to modify or edit bitmap graphics.– Modify individual pixels to:

• Retouch photographs• Wipe out red eye• Erase rabbit ears

• PC storage requires a considerable amount of storage space.– Solid State card to PC Hard Drive/CD/DVD…

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Image Resolution

• Expressed as the number of horizontal and vertical pixels.– Higher resolutions contain more data (larger file size) and

are higher quality.

• Bitmaps are resolution dependent.

• Changing the screen zoom level changesonly the size of the grid-no effect on the printed size of the graphic or file size.

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Image Resolution

• When you increase the resolution of a bitmap, pixel interpolation may occur.– Some images may appear pixelated.

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Color Depth and Palettes

• Color depth is the number of colors available for use in an image.

• Increasing color depth increases file size.– Monochrome bitmap– True Color bitmap (24-bit bitmap)

• 8 bits each for blue, green, red– 32-bit bitmap

• Color palettes are used to control color depth.– Grayscale palette– System palette– Web palette

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Color Depth and Palettes

• True Color bitmap – Each red, blue, and green pixel signal is assigned a value

form 0 to 255. 255=highest.– 16.7 million colors.

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Image Compression

• Any technique that recodes data in an image file so it contains fewer bits.– Lossless compression: Provides means to compress file then

reconstitute all data into its original state.• TIFF, PCX, GIF

– Lossy compression: Some data is lost during compression process. • JPEG

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Manual Image Compression Utility

• BMP and RAW Image formats don’t support compression.

• Popular file compression utilities, such as WinZip or PKZIP, zip one or more files into a new compressed file with a .zip extension.– Note: PNG, GIF, and JPEG hardly shrink for they are

already stored in compressed format.

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Bitmap Graphic Format Usage Guide

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Section C: Vector and 3-D Graphics

• Vector Graphics Basics

• Vector-to-Bitmap Conversion

• Vector Graphics on the Web

• 3-D Graphics

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Vector Graphic Basics

• Contain instructions for re-creating a picture.

• Vector graphics resize better than bitmaps.

• Vector graphics usually require less storage space than bitmaps.

• Vector graphics are not usually as realistic as bitmap images.

• It is easier to edit an object in a vector graphic than an object in a bitmap graphic.

• Powerpoint drawing objects are an example.

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Vector Graphic Basics

• Contain instructions for re-creating a picture.

• Vector graphics resize better than bitmaps.

• Vector graphics usually require less storage space than bitmaps.

• Vector graphics are not usually as realistic as bitmap images.

• It is easier to edit an object in a vector graphic than an object in a bitmap graphic.

• Powerpoint drawing objects are an example.

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Vector Graphic Basics

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Vector-to-Bitmap Conversion

• Rasterization superimposes a grid over a vector image and determines the color for each pixel.– Easy

• Tracing software locates the edges of objects in a bitmap image and converts the resulting shapes into vector graphic objects.– Difficult

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Vector Graphics on the Web

• SVG (Scalable Vector Graphics) and Flash are vector graphic formats for the Web.

• Advantages of using vector graphics.– Consistent quality– Text is Searchable– Compact file size

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3-D Graphics

• Stored as a set of instructions.– Contain locations and lengths of lines forming a wireframe

for a three dimensional object.

• Rendering is the process of covering a wireframe with surface color and texture.

• Ray Tracing adds light and shadows to a 3-D image.

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3-D Graphics

• 3-D graphics software provides tools for drawing a wireframe and then specifying colors and textures for rendering.

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Section D: Digital Video

• Digital Video Basics

• Producing Video Footage

• Video Transfer

• Video Editing

• Video Output

• Desktop, PDA, and Web Video

• DVD-Video

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Digital Video Basics

• Is composed of a series of bitmap graphics each called a frame.

• Uses bits to store color and brightness data for each video frame.

• Different kinds of digital videos (classified by using platform):– Desktop video– Web-based video– DVD-video– PDA video

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Digital Video Basics

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Producing Video Footage

• Use digital or analog video camera to shoot video footage.– Digital video cameras store

footage as a series of bits.• Videoconferencing cameras

(Web cam) attach directly to a computer.

– Analog video cameras store video signals as a continuous track of magnetic patterns.

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Tips for Producing Video Footage

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Video Transfer

• Video capture software controls the transfer process.– Video capture can be used to convert analog video signals

into digital format.

• Video capture software can:– Decrease video display size– Reduce the frame rate– Compress data

• Raw, uncompressed formats are ideal for editing.

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Video Editing-Edit Video Clops, Arrange Them on a Timeline, Specify a Soundtrack

• Linear editing– Requires at least two VCRs

• Nonlinear editing– Requires a computer hard disk and video editing sw.

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Video Output-Combining All Video and Audio Files into a Single File for Hard Disk Storage

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Video Output

• Video quality and file size can be affected by compression ratios and frame rate.

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Desktop, PDA, and Web Video

• You can add external or internet videos to a Web page.

• Internet connection speed affects Web videos.– Streaming video: sends small segments sequentially.

• Web video formats include MPEG4, MOV, ASF, and RM.

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DVD-Video

• Incorporate digital videos onto DVDs with interactive menus.– DVD authoring software and Writable DVD drive required.

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DVD-Video

• DVD authoring software can generate MPEG-2 encoded video clips and menus, store them in VOB files, and lay them out on a DVD according to industry standards.– With advance planning, menus are easy to create.– Output video in DVD-video format.

• A DVD Image/Volume is a prototype of your DVD.– Stored on your computer’s hard disk.– Thoroughly test DVD on your computer before you burn it.

• Recordable vs. rewritable DVDs.

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Section E: Digital Rights Management (DRM)

• DRM Basics

• Signal Scrambling and Digital Watermarks

• CD Copy Protection

• DVD DRM

• DRM for Digital Downloads

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DRM Basics

• Digital rights management (DRM) is a collection of techniques used by copyright holders to limit access and use of digital content.

• Affects:– Time shifting– Place shifting

• eg, Slingbox– Format shifting

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Signal Scrambling and Digital Watermarks

• Signal scrambling is a term commonly used for obscuring cable or satellite television images until they are unscrambled by a set-top box or other authorized mechanism.

• A digital watermark is a pattern of bits inserted at various places in an image or a content stream that can be used to track, identify, verify, and control content use.– Broadcast flag

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CD Copy Protection

• Copy protection refers to technologies designed to prohibit consumers from copying content.

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DVD DRM

• Copy Generation Management is a digital watermark that specifies the number of times a content stream can be duplicated.

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DVD DRM

• An Analog Protection System is any DRM technology that interjects signals into the video stream to prevent analog output from being copied. Prevents DVD to Tape to DVD copying.

• CSS (Content Scramble System) is a DRM technology designed to encrypt and control the use of content stored on DVDs.

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DVD DRM

• A DVD region code specifies geographical area of legitimate use for DVD disks and players.

• AACS (Advanced Access Content System) is a DRM technology designed to encrypt and protect content on optical disks. (Blu-ray, HD-DVD)

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DRM for Digital Downloads

• FairPlay to control music downloaded from the iTunes store.

• Microsoft supplies DRM technologies for several online music stores, including Zune.