CS 414

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CS 414 Multimedia Systems Design Lecture 19
Midterm Review Queue Management

• Klara Nahrstedt
• Spring 2012

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Midterm

• March 5 (Monday), 11-1150am, 1302 SC
• Closed Book, Closed Notes
• You can bring calculator and 1 page cheat sheet

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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 ),

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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

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Material

• Audio 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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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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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

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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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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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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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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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Sample Problems

• Describe briefly each step in MPEG-1 audio
  encoding. Specify the functionality, which is
  performed in each step. You dont have to provide
  equations, only a clear explanation of the
  functionality that is performed inside each step.

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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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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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Queuing , Queue management and rate control
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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
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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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Weighted Fair Queuing
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Weighted Fair Queuing
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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/(w1w2wn)

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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
  t0d, but packets can arrive any time t0 x
  between
• t0d, t0D .
• x is jitter

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Class-based WFQ
PQ Priority Queue
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Error Control Avoidance, detection, Correction
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Congestion Avoidance via Random Early
Drop(Active Queue Management)
RED Random Early Drop
Refined RED based on IP packet preference is
Weighted RED (WRED)
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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

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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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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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Go-back-N Retransmission
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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