Module Code: ELEC5611M01
Question 1[Page limit: maximal length of the answer for this question is three pages]
(a) Differentiate between ‘Lossy’ and ‘Lossless’ compression algorithms. Give an example of each.
(b) Calculate the number of bits per pixel with the following colour spaces:
(ii) Y:Cr:Cb 4:4:4
(iii) Y:Cr:Cb 4:2:2
(c) Using Huffman coding obtain codewords for 4 symbols with the following probability:
(d) Pulse Code Modulation (PCM) is the basic analog-to-digital conversion method for audio signals.
Give one enhancement to PCM and explain how it achieves further compression.
Question 2 [Page limit: maximal length of the answer for this question is three pages]
(a) The five main stages of the JPEG image coding algorithm are shown in the diagram below:
(i) Explain the function of the Image/block preparation stage.
(ii) How does the Discrete Cosine Transform (DCT) help to achieve compression?
(iii) How does the quantization stage contribute to compression?
(iv) What algorithms are used in the entropy coding stage to encode the quantized DC and AC
coefficients of the DCT?
(b) In relation to 3D video coding, define depth maps and explain how they are used to encode 3D videos.
(c) This question concerns the DVB-T digital television system.
(i) List three signals that the Programme Stream for a TV station will contain.
(ii) Describe in outline the stages by which signals from several TV stations are combined into a
Transport Stream, i.e. Multiplex. Do not describe how packetisation works.
(d) Every DVB packet contains a PID (packet identifier).
(i) Describe briefly what the PID identifies. Where in the packet is it stored?
(ii) When a TV receiver knows the PID of a packet it needs, how does it get this packet from the
stream of packets received?
(iii) Consider a TV receiver which needs to find the sound and vision packets of the TV station it is
displaying. How does it find the PIDs of the Program Allocation Table (PAT), Programme Map
Table (PMT), and the sound and vision packets which it needs?
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