Video Technology

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Video Technology 

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Question 1 (Total 25 Marks)

This question examines your understanding of the different number system representations and the properties of the sampling theorem.

(a) Demonstrate your understanding of number system representations by converting the following decimals to binary numbers. Note that the integer part of the binary representation is 8-bits in length.

(i) 26

(ii) -26

(iii) 4.625

(iv) -4.625

(8 marks)

(b) A representation of the A/D system in frequency domain is given in Figure Q1(b). The frequency domain representation of an input signal to the A/D system is depicted in the same figure.

(i) Describe frequency domain representation of the output from the A/D converter system by means of a diagram.

(6 marks)

(ii) What would cause aliasing during the A/D conversion? Sketch the frequency domain representation of the output from the A/D system if aliasing occurs during conversion.

(5 marks)

(c) Differentiate between progressive scan and interlaced scan through a brief explanation.

(6 marks)

Question 2 (Total 25 Marks)

This question will assess your understanding of video signal parameters, chroma sampling and how to carry out raw video data rate calculations.

(a) It is well known that human eyes are more sensitive to luminance than chrominance. Chroma subsampling (Color subsampling) is a useful tool in video encoding process. Draw the diagram of a 4:2:0 co-site sampling scheme.

(5 marks)

(b) There is a CIF video sequence with format 352x288@120I. The colour sampling scheme is 4:2:0. Each pixel is encoded into 8 bits. Determine the raw bit rate of this CIF video sequence.

(5 marks)

(c) In a typical MPEG-2 video system, there are 3 types of frames, which are I-frame, P-frame and B-frame respectively.

(i) Briefly describe the function of each frame type.

(5 marks)

(ii) From Figure Q2(c)(ii), showing a MPEG-2 Group of pictures (GOP), determine the encoding sequence of the GOP.

(5 marks)

(d) List TWO SD video formats and THREE HD video formats.

(5 marks)

Question 3 (Total 25 Marks)

This question assesses your ability to apply knowledge of components of the video codec, frame types, reference frames and decoding sequence for recording and broadcast applications.

(a) H.261 is the first video coding standard, which was targetted for teleconference over ISDN. Draw the block diagram of a H.261 encoder and briefly explain function of each block.

(6 marks)

(b) List at least 3 possible techniques we can deploy in order to improve the H.261 coding efficiency.

(5 marks)

(c) Video coding is implemented in a layered structure. Among those layers, the highest layer is video sequence, followed by Group of Pictures (GOP).

(i) List the remaining 4 layers

(4 marks)

(ii) Determine the level in which DCT is performed and which level when ME/MC is performed.

(2 marks)

(d) Given an HD video format (1920x1080@30P), calculate the total number of macroblocks (MBs) in luminance plane.

(4 marks)

(e) Explain the human sight deficiency of colour-blindness.

(4 marks)

Question 4 (Total 25 Marks)

This question examines your understanding of the terms, transmission errors and video broadcasting techniques.

(a) With the help of diagrams, briefly explain the concepts of True Video-on-Demand and Near Video-on-Demand.

(6 marks)

(b) With the aid of an example, briefly explain how a parity bit can correct transmission errors.

(6 marks)

(c) Why is modulation is applied before signal transmission and demonstrate your understanding of how DQPSK coding functions.

(7 marks)

(d) Draw the block diagram of a DVB transmission system and briefly explain the function of each component.

(6 marks)