1.2. Multimedia

Question 1

Bitmap Images

Answer 1

• Data for a bitmapped image is encoded by assigning a
  solid colour to each pixel, i.e., through bit patterns.
• Bit patterns are generated by considering each row of
  the grid as a series of binary colour codes which
  correspond to each pixel’s colour.
• These bit patterns are ‘mapped’ onto main memory
• Pixels: smallest picture element whose colour can be
  accurately represented by binary
• Bitmap image also contains the File Header which
  has the metadata contents of the bitmap file,
  including image size, number of colours, etc.

Question 2

Image Resolution

Answer 2

• Pixel density which is measured by no. of pixels/cm
• If image resolution increases, then image is
  sharper/more detailed

Question 3

Screen Resolution

Answer 3

• Number of pixels which can be viewed horizontally &
  vertically on the device’s screen
• Number of pixels = width × height

Question 4

Colour depth

Answer 4

• Number of bits used to represent the
  colour of a single pixel
• Convert bits to bytes by dividing by 8 if necessary.

Question 5

Applications of Colour Depth

Answer 5

scanned images and general computer
usage ∵ small file size and can be easily manipulated.

Question 6

Vector Graphics

Answer 6

• Made up of drawing objects
• Drawing objects: a mathematically defined construct
  (of shapes like rectangle, line, circle, etc.)
• Drawing list: set of commands defining the vector
• Properties of each object are the basic geometric data
  which determine the shape and appearance.
• Data is encoded using mathematical formulas to
  generate properties in order to draw lines & curves to
  create the image
• If object is resized, properties are recalculated.
• Scalable without losing quality unlike bitmaps

Question 7

Applications of Vector Graphics

Answer 7

Company logos

Question 8

Sound

Answer 8

• Analogue data is continuous electrical signals whereas
  digital data is discrete electrical signals.
• Sound signals are vibrations through a medium.
  Hence are analogue in nature as there can be an
  infinite amount of detail for sound.
• Analogue signals converted (encoded) to digital
  signals by sampling:

Question 9

Sampling

Answer 9

• Sound wave’s amplitude (height) sampled at set
  time intervals
• These samples (amplitudes) are encoded as a
  binary number sequence
• This sequence provides a digital representation of
  the sound wave

Question 10

Sampling Rate

Answer 10

• Number of samples taken per unit time
• Increasing the sampling rate increases accuracy of
  digitized sound wave representation but increases the
  file size

Question 11

Sampling Resolution

Answer 11

• Number of bits used to encode each sample
• Increasing sampling resolution increases accuracy of
  digitized sound wave but increases the file size

Question 12

Bit Rate

Answer 12

• no. of bits for storing 1 second of sound
• Bit Rate = Sampling Rate × Sampling Resolution

Question 13

File size

Answer 13

Bit Rate * Length of Sound