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ICT F.4 Ch. 4 Multimedia Elements and Digitization - Coggle Diagram
ICT F.4 Ch. 4 Multimedia Elements and Digitization
4.1 Digital Multimedia Elements
graphics
bitmaps
A bitmap image is a collection of colour dots called pixels arranged in rows and columns.
A pixel is the smallest picture element that can be shown on a computer screen.
The number of colours can be displayed in a pixel is determined by the number of bits used to represent the pixel (known as color depth).
The larger the color depth, the larger the number of colours can be displayed in the image.
resoution
Is the measurement of the number of pixel per unit length in
a bitmap image.
Is measured by pixel per inch(ppi).
The higher the resolution, the more details of the image can be shown. But the file size of a n image will increase dramticallly.
The higher the resoution, the more details of the image can be
shown. But the file size of an image will increase dramatically.
Digital images for screen display are usually stored at a resolution
ranging from 72 to 95 ppi.
Vector graphics
They are composed of a number of objects
A vector object can be a shape, a line or a string of a text
The shape and location of vector objects are defined by mathematical forumale
Can rescale and modify every detail of each vector
object easily without affecting the quality of vector graphics.
The file size of vector graphics does not grow rapidly even when
more and more vector objects are drawn in the image.
The file size of vector graphics is usually much smaller than that of a bitmap image.
audio
Audio files in a computer are the digitized data of music, speech and any kind of audio signals.
The quality of a digital audio file is determined by its bit resolution and sampling rate..
Bit resoultion
is the number of bits used to represent the amplitude of an audio signal.
The higher the number of bits used, the more precise the amplitude of the audio signal will be.
Sampling rate
Is the number of samples taken each second during the conversion process
Is measured by Hz
The higher the sampling rate, the better the quality of the digital audio will be.
Stereo audio contains two streams of audio signals, known as left sound track and right sound track.
Mono audio contains only one sound track.
Audio data can be stored either in uncompressed or compressed format.
WMA is the most popular type of uncompressed audio file format.
WMA and MP3 are examples of compressed audio widely used in portable music players and web pages.
video
Is a sequence of full-motion images together with sound tracks
The file size of it can be very large.
Factors affection the size of a video file
The higher the frame size and frame rate, the better the video quality and the larger the file size.
A particular compression method has its own specification of compression, frame sizes and frame rates.
Different video file formats require different media players and plug-ins
AVI is the most popular standard of uncompressed video file formats.
MPEG-1, MPEG-2 and WMV are examples of compressed video file formats.
Video files can be compressed info different video file formats for different playback media.
4.2 Analogue Data and Digital Data
Applications of digital data in IT
All electronic devices including computers and modern data transmission channels handle data in binary forms
Video and computer programs can be represented in sequences of binary numbers.
This makes operations of electronic devices on digital data such as storage, transmission, manipulation and duplication highly precise and efficient.
Conversation between analogue data and digital data
Digitization is the process of converting analogue data into digital data.
Digitization involves two procedures: namely sampling and quantisation
Sampling: The process of obtaining discrete sample data from the continuous analogue signal for every fixed time interval.
Quantisation: The process of converting the attribute of each sample data info a digital code using a predefined scale
Conversion of analogue multimedia elements
Audio
Sound is inherently analogue.
A sound card is an electronic circuit board that is responsible for conversion.
Digital audio files can be stored in a : large variety of file formats, for example, WAV, MP3, WMA and RA
The quality of digital audio is determined by sampling rate, the bit resolution, the number of channels
Image
Analogue images such as photographs or printed materials can be converted into digital images using a scanner.
The scanned images are stored as bitmap graphics.
The quality of a bitmap graphic is determined by resolution, colour depth and compression ratio
No matter what the scanning settings are, the scanned digital image cannot be the same as the original analogue source.
There is always a loss in information during the digitization process. Printing a digital image on paper and projecting it on a screen are examples of conversion of digital images into analogue images.
Video
To capture television programmes into a computer, we need a TV tuner card to receive TV signals from the antenna.
A TV tuner card converts analogue TV signals into a sequence of digital images and digital audio.
A video capture card works in a similar fashion except that it receives video sources instead of radio frequencies.
Example of video sources: video cassette record(VCR), digital video camera, web cam and digital camera
he quality of a digital video is determined by the frame size, frame rate and the video compression algorithm.