Multimedia def. Many forms

Multimedia Text Hyperlinks Images Audio Animation Video Text Hyperlinks Images Audio Animation Video

Text Text refers to letters, numbers, and other characters whose meaning is not specified (open to human interpretation) Text in a multimedia product is written using a word processor How much text should be included in your presentation? The screen should not be overloaded with text. Text refers to letters, numbers, and other characters whose meaning is not specified (open to human interpretation) Text in a multimedia product is written using a word processor How much text should be included in your presentation? The screen should not be overloaded with text.

Hypertext Allows the user to easily navigate through a multimedia product using cross-links Hyperlink- (link or hotword) is a highlighted word or graphic which allows electronic connection to a related article. Provides interactivity in a multimedia context Most common use is on the Internet. Allows the user to easily navigate through a multimedia product using cross-links Hyperlink- (link or hotword) is a highlighted word or graphic which allows electronic connection to a related article. Provides interactivity in a multimedia context Most common use is on the Internet.

Images Pictures such as drawings, paintings, photographs. Used to present information and provide interest. Al images on screen are made up of pixels (picture elements) Pictures such as drawings, paintings, photographs. Used to present information and provide interest. Al images on screen are made up of pixels (picture elements)

Bit mapped Images Bit-Mapped graphics treat each pixel on the screen individually and represent this by bits in memory. When transformed, they lose resolution Enlarging each pixel will create a staircase pattern called aliasing. Require Larger amounts of storage. Often stored in compressed formats such as GIF, JPEG Bit-Mapped graphics treat each pixel on the screen individually and represent this by bits in memory. When transformed, they lose resolution Enlarging each pixel will create a staircase pattern called aliasing. Require Larger amounts of storage. Often stored in compressed formats such as GIF, JPEG

Vector graphics Are made up of drawn objects such as lines, shapes. Each object is defined by characteristics such as position, line width, pattern. These characteristics are stored as mathematical expressions and displayed on the screen as pixels. Common formats include CGM, EPS, WMF. Are made up of drawn objects such as lines, shapes. Each object is defined by characteristics such as position, line width, pattern. These characteristics are stored as mathematical expressions and displayed on the screen as pixels. Common formats include CGM, EPS, WMF.

Graphics and Colours Colour graphics and graphics with tones (grey scale) increase the number of bits per pixel and require more storage space. Colours are obtained from a RGB screen (red, green, blue) which uses various percentages of red, green and blue to create all colours. The minimum number of colours is eight: red only, green only, blue only, red and green (yellow), red and blue (magenta), blue and green (cyan), all colours RGB (white) and no colours (black). Colour graphics and graphics with tones (grey scale) increase the number of bits per pixel and require more storage space. Colours are obtained from a RGB screen (red, green, blue) which uses various percentages of red, green and blue to create all colours. The minimum number of colours is eight: red only, green only, blue only, red and green (yellow), red and blue (magenta), blue and green (cyan), all colours RGB (white) and no colours (black).

Graphics and Colours A bit depth of 8 lets a graphic contain 256 colours, 64 colours each with 4 tones. (64 x 4 = 256) Or 32 colours each with 8 tones (32 x 8 = 256)  Photorealistic images require at least 24 bit colour.  Question: What is the file size in Kilobytes of a 256 colour image with a resolution of 1024 by 768 pixels? A bit depth of 8 lets a graphic contain 256 colours, 64 colours each with 4 tones. (64 x 4 = 256) Or 32 colours each with 8 tones (32 x 8 = 256)  Photorealistic images require at least 24 bit colour.  Question: What is the file size in Kilobytes of a 256 colour image with a resolution of 1024 by 768 pixels?

Answer: File size = Horizontal x Vertical x Bit depth 8 x x 768 x 8 = 768 kb = =

Audio Sound travels through air waves with particular volume and pitch A sound wave is analogue data. Analogue data is represented by continuous variable quantities whilst digital data is represented in the form of digits or numbers. As computers are digital, sound waves must be digitised. This is created using an analogue to digital converter (ADC) and reversed by a digital to analogue converter (DAC). The ADC and DAC are built into the computer. Sound travels through air waves with particular volume and pitch A sound wave is analogue data. Analogue data is represented by continuous variable quantities whilst digital data is represented in the form of digits or numbers. As computers are digital, sound waves must be digitised. This is created using an analogue to digital converter (ADC) and reversed by a digital to analogue converter (DAC). The ADC and DAC are built into the computer.

Sound Waves Sound waves are recorded by air being compressed and expanding. Y axis represents air pressure and x axis represents time Zero Line: represents the rest state Amplitude: the amount of compression or rarefaction at any point on the waveform. It is the distance above or below the zero line. Cycle: the amount of time it takes for the amplitude of the waveform to return to the same level. Frequency: the number of cycles that happen every second. The higher the frequency, the higher the pitch. Sound waves are recorded by air being compressed and expanding. Y axis represents air pressure and x axis represents time Zero Line: represents the rest state Amplitude: the amount of compression or rarefaction at any point on the waveform. It is the distance above or below the zero line. Cycle: the amount of time it takes for the amplitude of the waveform to return to the same level. Frequency: the number of cycles that happen every second. The higher the frequency, the higher the pitch.

Sampling At regular intervals the ADC measures the analog signal and outputs a number representing the amplitude of the signal at that precise instant. This is called a "sample." Before long there are a huge number of samples all arranged in chronological order like a spot-map of the original waveform.

Sampling Sampling rate: The number of times a sample (slice) is taken from the sound wave. During a sample the amplitude (volume) is measured and converted to a number. Common sampling rates are: 44.1kHz (44100 x sec) and (22050 x sec) Sample size (bit resolution) is the number of bits per sample. CD’s are recorded usually at 16 bits, however for normal voice recording 8 bits is sufficient. Sampling rate: The number of times a sample (slice) is taken from the sound wave. During a sample the amplitude (volume) is measured and converted to a number. Common sampling rates are: 44.1kHz (44100 x sec) and (22050 x sec) Sample size (bit resolution) is the number of bits per sample. CD’s are recorded usually at 16 bits, however for normal voice recording 8 bits is sufficient. 8 bit voice recording

Sample rate Sampling rateBest uses 11 kHzSpeech and short segments of music 22 kHzBetter music playback 32 kHzBroadcast audio standard 44 kHzCD quality playback 48 kHzDigital Audio Tape (DAT) playback

DAC Output for DAC with reconstructed waveform It has some information missing (at about 22 kHz), however this is out of the hearing range of humans (about 16kHz max) Output for DAC with reconstructed waveform It has some information missing (at about 22 kHz), however this is out of the hearing range of humans (about 16kHz max)

Mono and Stereo Mono uses one channel of sound and stereo uses 2 (left and right) File size is calculated by multiplying the sample rate, sample size and time. If the file is stereo, times this by two. Question: Calculate the file size of a CD quality audio that uses a sample rate of 44.1kHz with a 16 bit sample size and a four minute track in stereo. Mono uses one channel of sound and stereo uses 2 (left and right) File size is calculated by multiplying the sample rate, sample size and time. If the file is stereo, times this by two. Question: Calculate the file size of a CD quality audio that uses a sample rate of 44.1kHz with a 16 bit sample size and a four minute track in stereo.

WAV vs MP3 (storage) The large size of CD quality audio files can be a problem, but it is addressed using MP3’s which are a compressed audio format. It filters out excess information with no apparent reduction in quality. Audio track timeWAVMP mins42.4 Mb3.5 Mb 3.33 mins36 Mb3 Mb 8.16 mins83.5 Mb6.95 Mb

Animation

Animation is the creation of moving images. It is affected by image quality and speed of movement. Different types of animation include: Cell based animation Path based animation Morphing and warping Animation is the creation of moving images. It is affected by image quality and speed of movement. Different types of animation include: Cell based animation Path based animation Morphing and warping

Cell based animation Cell based animation involves drawing and displaying individual frames or cells. Each frame is saved and stored separately and loaded into a graphics page of primary memory. This is the traditional animation method. This animation method requires a very powerful computer to create and display 30 frames per second. Eg. A high-res colour graphic containing 30 fps would require calculations of 15million ( x 30) pixels in one second. Cell based animation involves drawing and displaying individual frames or cells. Each frame is saved and stored separately and loaded into a graphics page of primary memory. This is the traditional animation method. This animation method requires a very powerful computer to create and display 30 frames per second. Eg. A high-res colour graphic containing 30 fps would require calculations of 15million ( x 30) pixels in one second.

Cell based animation How it Works: The animation works by displaying the first frame from a graphics page, and at the same time creating the second frame. The second frame is then displayed whilst the third frame is being drawn. How it Works: The animation works by displaying the first frame from a graphics page, and at the same time creating the second frame. The second frame is then displayed whilst the third frame is being drawn.

Path based animation Involves displaying the movement of objects onto a fixed background in a particular sequence or path The background pixels do not change, only the pixels of the moving object change. This saves memory and processing time. To create, the moving object must be drawn once at the start point, saved, erased and drawn at the end point. Animation software can then fill in intermediate frames by “tweening”. Involves displaying the movement of objects onto a fixed background in a particular sequence or path The background pixels do not change, only the pixels of the moving object change. This saves memory and processing time. To create, the moving object must be drawn once at the start point, saved, erased and drawn at the end point. Animation software can then fill in intermediate frames by “tweening”.

Video and Still frame animation Frames Per Second Uses 8 FPSMinimum speed needed for the illusion of movement 12 FPSAnimation Speed 24 FPSMovie/film frame speed 30 FPSRefresh rate of computer monitors

Morphing (and warping) Morphing is the smooth change between two images Warping is the distortion of one portion of one image

Animation Links animation5.htm animation5.htm animation5.htm animation5.htm

Video Processing Videos are an interactive and dynamic medium which is especially beneficial for displaying and explaining concepts. However, video places huge demands on a multimedia system. The decision to include video mediums for their exciting additional elements can only be made as long as the system is able to support video effectively. Videos are an interactive and dynamic medium which is especially beneficial for displaying and explaining concepts. However, video places huge demands on a multimedia system. The decision to include video mediums for their exciting additional elements can only be made as long as the system is able to support video effectively.

Video Hardware A video camera (analogue or digital) is used to capture information

Video Storage Large videos and animations require large storage facilities. Number of Frames = FPS x Time in seconds eg. 24fps x 30 mins = 24 x (30 x 60) = frames  File size for each frame = Horizontal x vertical x bit depth (then convert to bytes and Kb) Large videos and animations require large storage facilities. Number of Frames = FPS x Time in seconds eg. 24fps x 30 mins = 24 x (30 x 60) = frames  File size for each frame = Horizontal x vertical x bit depth (then convert to bytes and Kb)

Video Storage continued A frame size of 2048 by 872 and 32 bits =2048 x 872 x 32 /(8 X 1024) =6976 KB  File size for movie = Frames x Size =43200 x 6976 =… A frame size of 2048 by 872 and 32 bits =2048 x 872 x 32 /(8 X 1024) =6976 KB  File size for movie = Frames x Size =43200 x 6976 =…