CS 414 - Spring 2012 CS 414 – Multimedia Systems Design Lecture 19 – Midterm Review + Queue...
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Transcript of CS 414 - Spring 2012 CS 414 – Multimedia Systems Design Lecture 19 – Midterm Review + Queue...
CS 414 - Spring 2012
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
CS 414 - Spring 2012
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
Material Media Characteristics
Synchronous, Isochronous, AsynchronousRegular, irregularWeakly and strongly periodic streams
Audio CharacteristicsSamples, frequency,Perception, psychoacoustic effects, loudness, pitch,
decibel, intensitySampling rate, quantization
CS 414 - Spring 2012
Material
Audio CharacteristicsPCM, DPCM, ADPCM, signal-to-noise ratio
Image CharacteristicsSampling, quantization, pixels Image properties: color, texture, edgesSimple edge detection process
CS 414 - Spring 2012
Material
Video technology Color perception: hue, brightness, saturation,Visual representation: horizontal and vertical
resolution , aspect ratio; depth perception, luminance, temporal resolution and motion
Flicker effectColor coding: YUV, YIQ, RGBNTSC vs HDTV formats
CS 414 - Spring 2012
Material Basic Coding schemes
Run-length codingStatistical coding
Huffman coding Arithmetic coding
Hybrid codesJPEG: image preparation, DCT
transformation, Quantization, entropy coding, JPEG-2000 characteristics
CS 414 - Spring 2012
Material
Hybrid CodingVideo 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
Material
Quality of Service conceptsService 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
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
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
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
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
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
QUEUING , QUEUE MANAGEMENT AND RATE CONTROL
CS 414 - Spring 2012
Covered Aspects of Multimedia
Image/VideoCapture
MediaServerStorage
Transmission
CompressionProcessing
Audio/VideoPresentationPlaybackAudio/Video
Perception/ Playback
Audio InformationRepresentation
Transmission
AudioCapture
A/V Playback
Image/Video InformationRepresentation
Rate Control
Multimedia networks use rate-based mechanisms (conventional networks use window-based flow control and FIFO)
CS 414 - Spring 2012
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
Weighted Fair Queuing
CS 414 - Spring 2012
Weighted Fair Queuing
CS 414 - Spring 2012
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
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
CS 414 - Spring 2012
Class-based WFQ
CS 414 - Spring 2012
PQ – Priority Queue
ERROR CONTROL: AVOIDANCE, DETECTION, CORRECTION
CS 414 - Spring 2012
Congestion Avoidance via Random Early Drop(Active Queue Management)
RED = Random Early Drop
Refined RED based on IP packet preference is Weighted RED (WRED)
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
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
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
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
CS 414 - Spring 2012