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CS 414 – Multimedia Systems Design Lecture 19 – Midterm Review + Queue Management

CS 414 – Multimedia Systems Design Lecture 19 – Midterm Review + Queue Management. Klara Nahrstedt Spring 2012. Midterm. March 5 (Monday), 11-11:50am, 1302 SC Closed Book, Closed Notes You can bring calculator and 1 page cheat sheet. Covered Material. Class Notes (Lectures 1-16) MP1

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CS 414 – Multimedia Systems Design Lecture 19 – Midterm Review + Queue Management

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  1. CS 414 – Multimedia Systems DesignLecture 19 – Midterm Review + Queue Management Klara Nahrstedt Spring 2012 CS 414 - Spring 2012

  2. Midterm March 5 (Monday), 11-11:50am, 1302 SC Closed Book, Closed Notes You can bring calculator and 1 page cheat sheet CS 414 - Spring 2012

  3. Covered Material • Class Notes (Lectures 1-16) • MP1 • Book Chapters to read/study: • Media Coding and Content processing book • Chapter 2, • Chapter 3.1-3.2, 3.8, • Chapter 4.1-4.2.2.1, • Chapter 4.3 (as discussed in lecture) • Chapter 5, chapter 7.1-7.5, 7.7 • Multimedia Systems book • Chapter 2.1-2.4, (not 2.4.4 – we have not covered QoS routing ), CS 414 - Spring 2012

  4. Material • Media 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 CS 414 - Spring 2012

  5. Material • Audio Characteristics • PCM, DPCM, ADPCM, signal-to-noise ratio • Image Characteristics • Sampling, quantization, pixels • Image properties: color, texture, edges • Simple edge detection process CS 414 - Spring 2012

  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 CS 414 - Spring 2012

  7. Material • Basic Coding schemes • Run-length coding • Statistical coding • Huffman coding • Arithmetic coding • Hybrid codes • JPEG: image preparation, DCT transformation, Quantization, entropy coding, JPEG-2000 characteristics CS 414 - Spring 2012

  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 CS 414 - Spring 2012

  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 CS 414 - Spring 2012

  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 CS 414 - Spring 2012

  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 CS 414 - Spring 2012

  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. CS 414 - Spring 2012

  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 CS 414 - Spring 2012

  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 CS 414 - Spring 2012

  15. Queuing , Queue management and rate control CS 414 - Spring 2012

  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

  17. Rate Control Multimedia networks use rate-based mechanisms (conventional networks use window-based flow control and FIFO) CS 414 - Spring 2012

  18. Weighted Fair Queuing CS 414 - Spring 2012

  19. Weighted Fair Queuing CS 414 - Spring 2012

  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) CS 414 - Spring 2012

  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 t0over 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+ xbetween [t0+d, t0+D] . • x is jitter CS 414 - Spring 2012

  22. Class-based WFQ PQ – Priority Queue CS 414 - Spring 2012

  23. Error Control: Avoidance, detection, Correction CS 414 - Spring 2012

  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. CS 414 - Spring 2012

  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 CS 414 - Spring 2012

  28. Go-back-N Retransmission CS 414 - Spring 2012

  29. Conclusion • Establishment 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 CS 414 - Spring 2012

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