1. Klara Nahrstedt Spring 2012
CS 414 – Multimedia Systems Design Lecture 19 – Midterm Review + Queue Management
Klara Nahrstedt
Spring 2012
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2. Midterm March 5 (Monday), 11-11:50am, 1302 SC
Closed Book, Closed Notes
You can bring calculator and 1 page cheat sheet
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3. Covered Material Class Notes (Lectures 1-16) MP1
Book Chapters to read/study:
Media Coding and Content processing book
Chapter 2,
Chapter , 3.8,
Chapter ,
Chapter 4.3 (as discussed in lecture)
Chapter 5, chapter , 7.7
Multimedia Systems book
Chapter , (not – we have not covered QoS routing ),
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4. Material Media Characteristics Audio Characteristics
Synchronous, Isochronous, Asynchronous
Regular, irregular
Weakly and strongly periodic streams
Audio Characteristics
Samples, frequency,
Perception, psychoacoustic effects, loudness, pitch, decibel, intensity
Sampling rate, quantization
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5. Material Audio Characteristics Image Characteristics
PCM, DPCM, ADPCM, signal-to-noise ratio
Image Characteristics
Sampling, quantization, pixels
Image properties: color, texture, edges
Simple edge detection process
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6. Material Video technology
Color perception: hue, brightness, saturation,
Visual representation: horizontal and vertical resolution , aspect ratio; depth perception, luminance, temporal resolution and motion
Flicker effect
Color coding: YUV, YIQ, RGB
NTSC vs HDTV formats
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7. Material Basic Coding schemes Hybrid codes Run-length coding
Statistical coding
Huffman coding
Arithmetic coding
Hybrid codes
JPEG: image preparation, DCT transformation, Quantization, entropy coding, JPEG-2000 characteristics
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8. Material Hybrid Coding
Video MPEG: image preparation, I, P, B frames characteristics, quantization, display vs processing/transmission order of frames
Audio MPEG: role of psychoacoustic effect, masking, steps of audio compression
MPEG-4: differences to MPEG-2/MPEG-1
Audio-visual objects, layering
H.261, 263, 264
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9. Material Quality of Service concepts
Service classes, QoS specification – deterministic, predictive, best effort, QoS classification – application, system, network QoS, relation between QoS and resources
QoS operations: translation, negotiation of QoS parameters
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10. Material Resource Management concepts
QoS and resources, establishment phase and transmission/enforcement phase
Admission control of resources, reservation and allocation of resources
Negotiation Protocols
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11. Sample Problems
Consider the following alphabet {C,S,4,1}, with probabilities: P(C) = 0.3, P(S) = 0.2, P(4)= 0.25, P(1) = 0.25.
Encode the word CS414 using
Huffman coding and arithmetic coding
Compare which encoding requires less bits
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12. Sample Problems
Describe briefly each step in MPEG-1 audio encoding. Specify the functionality, which is performed in each step. You don’t have to provide equations, only a clear explanation of the functionality that is performed inside each step.
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13. Sample Problems What is flicker effect and how to remove it?
Explain difference between synchronous and isochronous transmission stream modes
Provide five differences between MPEG-4 video encoding standard and the previous MPEG video encoding standards
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14. Sample Problems
Consider voice conversational application (like Skype). What multimedia-sensitive algorithms at the setup phase would you deploy to make sure that you start with a good voice transmission ? Specify clear design of order of algorithms/protocols to be used
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15. Queuing , Queue management and rate control
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16. Covered Aspects of Multimedia
Audio/Video
Presentation
Playback
Image/Video
Capture
Audio/Video
Perception/ Playback
Image/Video Information
Representation
Transmission
Transmission
Compression
Processing
Audio
Capture
Media
Server
Storage
Audio Information
Representation
A/V
Playback
ORCHID Research Group
Department of Computer Science, University of Illinois at Urbana-Champaign

17. Rate Control
Multimedia networks use rate-based mechanisms (conventional networks use window-based flow control and FIFO)
Work-conserving schemes
Non-work-conserving schemes
Fair Queuing
Jitter Earliest-Due-Date
Virtual Clock
Stop-and-Go
Delay Earliest-Due-Data
Hierarchical Round-Robin
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18. Weighted Fair Queuing
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19. Weighted Fair Queuing
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20. WFQ vs FQ
Both in WFQ and FQ, each data flow has a separate FIFO queue.
In FQ, with a link data rate of R, at any given time the N active data flows (the ones with non-empty queues) are serviced simultaneously, each at an average data rate of
R / N.
Since each data flow has its own queue, an ill-behaved flow (who has sent larger packets or more packets per second than the others since it became active) will only punish itself and not other sessions.
WFQ allows different sessions to have different service shares. If N data flows currently are active, with weights w1,w2...wN, data flow number i will achieve an average data rate of R * wi/(w1+w2+…+wn)
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21. WFQ and Jitter
WFQ guarantees packet delay less than a given value D, but as long as delay is within bound it does not guarantee what the delay will be
Example: send packet at time t0 over a path whose maximum delay is D (note that each path has some minimal delay d)
WFQ guarantees that packet arrives no sooner than t0+d, but packets can arrive any time t0+ x between
[t0+d, t0+D] .
x is jitter
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22. Class-based WFQ
PQ – Priority Queue
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23. Error Control: Avoidance, detection, Correction
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24. Congestion Avoidance via Random Early Drop (Active Queue Management)
RED = Random Early
Drop
Refined RED based on
IP packet preference is
Weighted RED (WRED)

25. Error Detection
Ability to detect the presence of errors caused by noise or other impairments during transmission from sender to receiver
Traditional mechanisms: check-summing, PDU sequencing
Checksum of a message is an arithmetic sum of message code words of a certain word length (e.g., byte)
CRC – Cyclic Redundancy Check – function that takes as input a data stream of any length and produces as output a value (commonly a 32-bit integer) – can be used as a checksum to detect accidental alteration of data during transmission or storage
Multimedia mechanisms: byte error detection at application PDU, time detection

26. Design of Error Correction Codes
Automatic repeat-request (ARQ)
Transmitter sends the data and also an error detection code, which the receiver uses to check for errors, and requests retransmission for erroneous data
The receiver sends ACK (acknowledgement of correctly received data)
Forward Error Correction (FEC)
Transmitted encodes the data with an error-correcting code (ECC) and sends the coded msg. No ACK exists.
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27. Error Control Error Correction
Traditional mechanisms: retransmission using acknowledgement schemes, window-based flow control
Multimedia mechanisms:
Go-back-N Retransmission
Selective retransmission
Partially reliable streams
Forward error correction
Priority channel coding
Slack Automatic Repeat Request
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28. Go-back-N Retransmission
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29. Conclusion Establishment Phase Transmission Phase
Negotiation, Translation
Admission, Reservation
Transmission Phase
Traffic Shaping
Isochronous Traffic Shaping
Shaping Bursty Traffic
Rate Control
Error Control
Next: Case Studies of Multimedia Protocols
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