2. Multimedia
• Multi’ means ‘more than one’
• ‘media’ represents the plural of ‘medium’
• Medium: an intermediate agency, instrument, or channel; especially a means
or channel of communication or expression
3. Categories of media
• Continuously in time
• Video belongs to this category ( sequence of video frames)
• Other examples ??
• Continuously in space
• Text is example of this category ( Discrete in nature)
• Other examples ??
• Multimedia is a combination of two or more media, one of which is discrete,
and the other continuous
4.
5. Interactive multimedia
• when a viewer of a multimedia presentation is allowed to control what
elements are delivered and when, it is interactive multimedia.
6. Digital multimedia
• Digitization
• Analogue Vs Digital
• Continuous signal is analogue like electricity
• Computer understands binary so we have to convert analogue into digits
• This process is known as digitization
7. Digital multimedia
• Sampling
• taking samples of the continuous signal. The number of samples taken during a time
period is known as the sampling rate.
• Quantization
• restrict the value of the samples to a fixed set of levels. The unit of sampling rate is
Hertz (Hz), i.e. 1Hz means taking one sample per second. We use KHz
8. Nyquist sampling theorem
• In order to reconstruct the signal, the sampling rate must not be less than
twice the maximum frequency of the original signal
• Under sample aliasing
• quantization error if few quantization levels
9. Analogue-to-digital converter
• a digital camera or a scanner
• a digital audio recorder
• a digital camcorder.
• Data size issue, compression
10. Sound
caused by vibration of material
pressure wave fluctuations in the air
move hair-like fibers in ear
electrical impulses sent to the brain
Brain coverts them to auditory sensations
11. Bandwidth
Bandwidth is the range of frequencies a device can produce or a human can hear
• FM radio 50 Hz – 15 kHz
• AM radio 80 Hz – 5 kHz
• CD player 20 Hz – 20 kHz
• Sound Blaster 16 sound card 30 Hz – 20 kHz
• Inexpressive microphone 80 Hz – 12 kHz
• Telephone 300 Hz – 3 kHz
• Children’s ears 20 Hz – 20 kHz
• Older ears 50 Hz – 10 kHz
• Male voice 120 Hz – 7 kHz
• Female voice 200 Hz – 9 kHz.
