PALESTINE POLYTECHNIC UNIVERSITY
COLLEGE OF ADMINISTRATIVE SCIENCES AND INFORMATICS
IT DEPARTMENT
5292– Multimedia
Second Exam
Eng. Abdalfatah Najjar
[email protected]
Second Semester 2009-2010
Student name:…………………………………………...…
Date: Saturday, May 15, 2010
Student number: ……………………………………….….
Time duration: 120 minutes
NOTES:
Please read these instructions carefully before you start.
Examination Paper Title: Multimedia
Duration: 2 hours
 ‫ﺍﻛﺘﺐ ﺍﺳﻤﻚ ﺍﻟﺜﻼﺛﻲ ﺑﺎﻟﻠﻐﺔ ﺍﻟﻌﺮﺑﻲﺓ‬
 Switch off your phones or any other noisy gadgets!
 This is a closed book exam. So, you are not allowed to have anything but a pen (pencil, eraser) and this
exam on your desk.
 Answers to be written in PEN (do not use red color).
 Answer questions in the space provided. Yours answers should be expressed clearly and to the point.
 No marks will be given for unclear answers or multiple answers.
Structure of Examination Paper:
There are 7 pages.
There are 3 questions in total and one pones question.
The maximum mark for the examination paper is 80 and the mark obtainable for a question or part of a
question is shown in brackets alongside the question.
Question No.
Question Grade
Grade
Q1
22
Q2
45
Q3
13
Q4
4
Total Grade
84
22
45
13
4
84
80
You got
U
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21
out of 20 points.
U
[Question#1] Chapter 4 Color in Image and Video (22 points)
A. Briefly explain how the human visual system senses color (Use a diagram with your explanation). How is
color exploited in the compression of multimedia graphics, images and video? ( 10 points)
Solution:
• The eye is basically just a “biological camera”
• Eye through lens etc focused light onto the Retina (back of eye)
• Retina consists of neurons that fire nerve signals proportional to incident light
• Each neuron is either a rod or a cone. Rods are not sensitive to color.
• Cones organized in banks that sense red green and blue
Multimedia Context:
Since Rods does not sense color only sense luminosity intensity Eye is more sensitive to
luminance than color? Also Eye is more sensitive to red and green and blue (this is due to
evolution need to see fellow humans where blue is not prevalent in skin hues) so any
Multimedia compression techniques should use color representation that presents color in
a way that models Human Visual system. We can then encode luminance is high
bandwidth (more bits) than color as this is much more perceptually relevant.
Another solution:
The eye is basically sensitive to color intensity
o Each neuron is either a rod or a cone . Rods are not sensitive to color.
o Cones come in 3 types: red, green and blue.
o Each responds differently --- Non linearly and not equally for RGB differently
to various frequencies of light.
‫ﻁﺒﻌﺎ ﺍﻟﺴﺆﺍﻝ ﺗﻢ ﺣﻠﻪ ﻋﻠﻰ ﺍﻟﻠﻮﺡ ﻭﻣﻨﺎﻗﺸﺘﻪ ﻓﻲ‬
‫ﺍﻟﻤﺨﺘﺒﺮ ﻭﻁﺒﺎﻋﺘﻪ ﻋﻠﻰ ﻭﺭﻗﺘﻴﻦ ﺑﺸﻜﻞ ﻣﺨﺘﻠﻒ‬
‫ﻛﻞ ﻣﺮﺓ ﻟﺘﻮﺿﻴﺢ ﺍﻟﻔﻜﺮﺓ‬
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B. List three distinct models of color used in Multimedia. Explain why there are a number of different color
models exploited in multimedia data formats. (5 points)
Possible models:
• RGB
• CIE Chromaticity
• YIQ Color Space
• YUV (YCrCb)
• CMY/CMYK
• HSI
‫ﺗﻢ ﺣﻠﻪ ﻋﻠﻰ ﺍﻟﻠﻮﺡ ﻓﻲ ﺍﻟﻤﺨﺘﺒﺮ ﻭ‬
‫ﺍﻳﻀﺎ ﺗﻢ ﺗﻮﺯﻳﻌﻪ ﻣﻄﺒﻮﻋﺎ ﻓﻲ‬
‫ﺍﻟﻤﺨﺘﺒﺮ ﻓﻲ ﻣﺤﺎﺿﺮﺓ ﺍﺧﺮﻯ ﻳﻌﻨﻲ‬
‫ﺗﻢ ﺷﺮﺡ ﺍﻟﺴﺆﺍﻝ ﻣﺮﺗﻴﻦ‬
1. Different models reflect need to represent color in a perceptually relevant model
for effective compression.
2. Different models also due to evolution of color from Video (YIQ,YUV), Display
(RGB) and Print (CMYK) media requirements.
C. What is the difference between lightness and brightness according to the human vision? (2 points)
Lightness: is the impression of black or white (the level of gray)
Brightness: is the impression of dark or light
‫ﺗﻢ ﺷﺮﺣﻬﻢ ﻓﻲ ﻣﺤﺎﺿﺮﺍﺕ‬
‫ﺍﻟﻤﺨﺘﺒﺮ ﻭ ﻛﺘﺎﺑﺘﻬﻢ ﻋﻠﻰ ﺍﻟﻠﻮﺡ‬
D. For each of the following questions, circle one answer out of the choices given. (5 points)
1. Color model for CRT and LCD displays :
1) RGB
2) CMY/K
3) YUV
4) YIQ
2. The following color model is subtractive color :
1) RGB
2) CMY/K
3) YUV
4) YIQ
3. the RGB values for white color is :
1) (0, 0, 0)
2) (255, 255, 255)
3) (0, 0, 255)
4) (255 ,0, 0)
4. The RGB values for black color is :
1) (0, 0, 0)
2) (255, 255, 255)
3) (0, 0, 255)
4) (255, 0, 0)
5. The theoretical CMY values for black is :
1) (100%, 100%, 100%)
2) (0%, 0%, 0%)
3) (50%, 50%, 50%)
4) (0%, 100%, 0%)
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[Question#2] Chapter 6 Basics of Digital Audio (45 points)
A. What does Nyquist’s Sampling Theorem state?
• In order to effectively sample a waveform the sampling frequency must be at least
twice that of the highest frequency present in the signal
B. What are the implications of Nyquist’s Sampling Theorem for multimedia data? (4 points)
• Sampling frequency affects the quality of the data ---- higher frequency equals better
sampling hence representation of the underlying signal (given fixed frequency range of
signal)
• Sampling frequency affects size of digitized data --- higher frequency means more
samples therefore more data.
C. An analog signal has bandwidth that ranges from 15Hz to 10 KHz. What is the rate of sampler and the
bandwidth of bandlimiting filter required if: (4 points)
1. The signal is to be stored within computer memory.(2 points)
Nyquist’s Sample Theorem rate says that sampling must be at least twice the highest
frequency component of signal or transmission channel.
Highest frequency is 10 KHz so
Sampling rate = 20 KHz or 20,000 sample per second.
Bandwidth of bandlimiting filter = 0 – 10 KHZ
2. The signal is to be transmitted over a network which has a bandwidth from 200Hz to 3.4 KHz.(2 points )
Channel has lower rate than max in signal so must choose this a limiting high frequency so
Sampling rate = 6.8 KHz or 6,800 sample per second.
Bandwidth of bandlimiting filter = 0 – 3.4 KHZ
‫ﺍﻟﺴﺆﺍﻝ ﺗﻢ ﺣﻠﻪ ﻳﻮﻡ ﺍﻟﺜﻼﺛﺎء ﻓﻲ‬
‫ﺍﻟﻤﺤﺎﺿﺮﺓ ﺑﺸﻜﻞ ﻛﺎﻣﻞ ﻛﻤﺎ ﻫﻮ‬
‫ﻧﺼﺎ ﻭﺧﺮﻓﺎ‬
D. It is known that a loss of audio output at both ends of the audible frequency range is inevitable due to the
frequency response functions of audio amplifier and medium (e.g., tape). (4 points)
1. If the output was 1 volt for frequencies at mid-range, after a loss of −3 dB at 18 kHz what is the output
voltage at this frequency? (3 point)
2. To compensate the loss, a listener can adjust the gain (and hence the output) at different frequencies from
an equalizer. If the loss remains −3 dB and a gain through the equalizer is 6 dB at 18 kHz, what is the
output voltage now? [Hint: Assume log102 = 0:3] (3 point)
‫ﻟﻠﻌﻠﻢ ﻁﺒﻌﺎ ﻫﺬﺍ ﺍﻟﺴﺆﺍﻝ ﺗﻢ ﺣﻠﻪ ﻓﻲ ﺍﻟﻤﺤﺎﺿﺮﺓ ﺑﺸﻜﻞ‬
‫ﻛﺎﻣﻞ ﻳﻮﻡ ﺍﻟﺜﻼﺛﺎء ﻭﻫﻮ ﺍﻟﺴﺆﺍﻝ ﺍﻟﺜﺎﻟﺚ ﻣﻦ ﺍﺳﺌﻠﺔ‬
‫ﺍﻟﻜﺘﺎﺏ ﻧﺼﺎ ﻭ ﺣﺮﻓﺎ ﺩﻭﻥ ﺍﻱ ﺗﻐﻴﻴﺮ‬
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E. A piece of music that lasts one- minute and has been recorded at CD quality Stereo audio. A stereo audio
has two channels-a left channel and a right channel. The bit depth of CD-quality audio is 16-bit per channel.
Its sample rate is 44.1 kHz. (4 points)
1. Calculate the audio file size in Mega Byte. (3 points)
File size = duration X sampling rate X bit depth X number of channels
= (1 X 60 ) X 44100
X 16
X2
= 8467200 bits
= 10584000 bytes
= 10MB
2. If we want to post this one-minute audio on the web. How much time does it take to download it with
1.5Mbps broadband speed? (3 points)
1 second --------------------------------1500000 bits
?????------------------------------------- 8467200 bits
So,
Time = 8467200 bits/ 1500000 = 56
seconds
‫ﻟﻠﻌﻠﻢ ﻫﺬﺍ ﺍﻟﺴﺆﺍﻝ ﻣﺤﻠﻮﻝ ﻓﻲ‬
‫ﺍﻻﻭﺭﺍﻕ ﺍﻟﺨﺎﺭﺟﻴﺔ ﺑﻨﻔﺲ‬
114+ 113 ‫ﺍﻻﺭﻗﺎﻡ ﺻﻔﺤﺔ‬
F. What is MIDI? How is a basic MIDI message structured? (6 points)
Definition of MIDI: a protocol that enables computer, synthesizers, keyboards, and other
musical device to communicate with each other.
Structure of MIDI messages:
• MIDI message includes a status byte and up to two data bytes.
• Status byte
• The most significant bit of status byte is set to 1.
• The 4 low-order bits identify which channel it belongs to (four bits produce 16 possible channels).
• The 3 remaining bits identify the message.
• The most significant bit of data byte is set to 0.
‫ﻧﺼﺎ ﻭ ﺣﺮﻓﺎ ﻣﻦ ﺍﻟﻤﺎﺩﺓ ﺍﻟﺘﻲ ﺗﻢ ﺷﺮﺣﻬﺎ‬
‫ﻓﻲ ﺍﻟﻤﺤﺎﺿﺮﺓ ﻋﻦ ﻣﻮﺿﻮﻉ‬
MIDI
G. We wish to develop a new Internet service, for doctors. Medical ultrasound is in the range 2-10 MHz; what should
our sampling rate be chosen as? Why??? (2 points)
2 X 10MHz which is 20MHz
U
U
according to Nyquist’s sampling theorem
H. For each of the following statements, determine whether it is either true or false. (5 points)
1. True False
MP3 is a good file format to keep as a source file for further editing.
U
U
False
2. True
U
Zero decibels are when there is no sound wave.
True
False
For SQNR larger value is better.
True
False
A waveform is a graphical representation of the pressure–time fluctuations of a sound wave.
3.
4.
U
U
U
U
U
5. True False
U
U
if you were standing 20 feet from a loudspeaker, and were to move to 40 feet away
from that loudspeaker, you would expect to see a drop in level of 3 dB.
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‫ﺣﺴﺐ ﻗﺎﻧﻮﻥ‬
Inverse Square Law
I. For each of the following questions, circle one answer out of the choices given. (12 points)
1. A sound with higher _____ is perceived to have a higher pitch.
A. volume
B. frequency
C. fidelity
D. sampling rate
E. bit depth
2. The human ear can respond to minute pressure variations in the air if they are in the audible frequency
range, roughly__________________.
A. 20 Hz - 20 kHz.
B. 20 mHz - 200 kHz.
C. 200 Hz - 20 kHz.
D. 20 Hz - 200Hz.
3. The INTENSITY LEVEL (threshold of pain )of a loud sound which gives pain to the ear, usually ______.
A. 140 dB
B. 180 dB
C. 0 dB
D. 20 dB
4. MIDI standard specifies _____.
A. the sampling rate for the synthesized sound
B. bit depth for the synthesized sound
C. the configurations of cables and cable
D. the format of the data
plugs
5. The reduction of a digital audio file size can be achieved by _____. (more than one answer)
A. reducing the sampling rate
B. reducing the pitch of the audio
C. reducing the bit depth
D. reducing the amplitude of the audio
E. applying file compression techniques
6. The unit used for measuring _____ is Hertz (Hz).
A. amplitude
B. frequency
D. bit depth
E. dynamic range
7. The horizontal axis of a waveform is _____.
A. distance
B. time
8. Which of the following file extensions indicate audio files? (more than one answer)
BMP
WAV JPEG AIFF MP3
GIF
JPG AU TIFF WMF
MIDI
9. In digital audio, the number of sample points taken per second is called _____.
A. amplitude
B. frequency
C. sampling rate
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D. bit depth
E. dynamic range
10. Increasing the sampling rate from 22.05 KHz to 44.1 KHz will _____ file size
A. Decrease
B. Double
C. Not affect
[Question#3] Chapter 8 and 9 Lossy compression algorithm (13 points)
A. Briefly outline the JPEG compression pipeline and the constituent compression algorithms employed
at each stage in the pipeline. (6 points for the diagram and 5 points for ordering the steps)
‫ﺗﻢ ﺷﺮﺣﻬﺎ‬
‫ﺑﺎﻟﻤﺤﺎﺿﺮﺓ ﻭ‬
‫ﺗﻮﺯﻳﻊ ﺍﻻﻭﺭﺍﻕ‬
‫ﺍﻟﺘﻲ ﺗﻮﺿﺢ‬
‫ﺍﻟﺮﺳﻤﺔ ﻣﺮﺗﻴﻦ‬
‫ﻭ ﺗﻢ ﺭﺳﻤﻬﺎ‬
‫ﻋﻠﻰ ﺍﻟﻠﻮﺡ ﻓﻲ‬
‫ﺍﻟﻤﺤﺎﺿﺮﺓ ﻣﻊ‬
‫ﺍﻟﺨﻄﻮﺍﺕ‬
Stages of JPEG:
•
•
•
•
•
•
•
•
RGB to YIQ --- colour subsampling into Y and subsampled I, Q channels
Discrete Cosine Transform --- converiion to frequency domain (no compression yet)
Quantisation --- “low pass” filter of DCT data using tables or uniform quantization
Zig-Zag Scan -- writes out a vector from each 8x8 block low
frequency coefficients first. (Maps 8 x 8 to a 1 x 64 vector)
Differential Pulse Code Modification (DPCM) on DC channel --- DC component is large and
varies but often close to previous value SO encode the difference from previous 8x8 blocks.
Run Length Encoding (RLE) -- applied to the AC component. Each 1x64 vector has lots of
zeros in it SO encode as RLE pairs
Entropy Coding (Huffman or Arithmetic) -- DC and AC components finally need to be
represented by a smaller number of bits so use Huffman or Arithmetic Coding compresson.
B. For each of the following statements, determine whether it is either true or false. (2 points)
1. True
False
The JPEG2000 standard use DWT (Discrete Wavelet Transform).
U
2. True
Page 7/8
U
False
U
U
The JPEG2000 standard uses Huffman coding.
[Question#4] Challenge Question:
Your solution must be clear, elegant and easy to understand. This is a binary question so you
will get full mark or zero.
Suppose that a digitized TV picture is to be transmitted from a source that use a matrix of 480X500 picture
elements (pixels), where each pixel can take on one of 32 intensity values. Assume that 30 pictures are sent per
second. Find The source rate (R) bps? (4 points)
Number of pixels in each picture = 480 X 500 = 240000 pixels
We have 30 picture per second
If 1 picture have ---------------------------- 240000 pixels
30 pictures -----------------------------------????????
So, 30 pictures have 30 X 240000 = 7200000pixels
Each pixel can take on one of 32 intensity values this is mean that every
1 pixel -------5 bits
Since 25 = 32
So,
1 pixel ------------------ 5 bits
7200000 pixels --------????
So, number of bits per second = 7200000 X 5 = 36000000 = 360Mbps
This is the required source rate.
‫ﺍﺗﻮﻗﻊ ﺑﻌﺪ ﻫﻴﻚ ﺍﺳﺌﻠﺔ‬
‫ﻋﻴﺐ ﻋﻠﻰ ﻁﺎﻟﺐ ﺍﻭ ﻁﺎﻟﺒﺔ‬
‫ﺍﻥ ﻳﺮﺳﺐ ﻓﻲ ﺍﻻﻣﺘﺤﺎﻥ ﺍﻭ‬
‫ﺍﻥ ﻻ ﻳﺤﺼﻞ ﻋﻠﻰ ﻋﻼﻣﺔ‬
‫ﺷﺒﻪ ﻛﺎﻣﻠﺔ ؟؟؟؟؟؟؟‬
‫ﻫﺬﺍ ﺍﻟﺴﺆﺍﻝ ﻣﺤﻠﻮﻝ ﻓﻲ‬
‫ﻭﺭﻗﺔ ﺧﺎﺭﺣﻴﺔ ﺗﻢ‬
‫ﺗﻮﺯﻳﻌﻬﺎ ﻗﺒﻞ ﺍﻻﻣﺘﺤﺎﻥ‬
!!!!!!!!!!!!! ‫ﺑﺎﺭﺑﻌﺔ ﺍﻳﺎﻡ‬
Good luck
Course instructors: Eng.Abdalfatah Najjar
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