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


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 ),


Material Media Characteristics

Synchronous, Isochronous, AsynchronousRegular, irregularWeakly and strongly periodic streams

Audio CharacteristicsSamples, frequency,Perception, psychoacoustic effects, loudness, pitch,

decibel, intensitySampling rate, quantization


Material

Audio CharacteristicsPCM, DPCM, ADPCM, signal-to-noise ratio

Image CharacteristicsSampling, quantization, pixels Image properties: color, texture, edgesSimple edge detection process


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


Material Basic Coding schemes

Run-length codingStatistical coding

Huffman coding Arithmetic coding

Hybrid codesJPEG: image preparation, DCT

transformation, Quantization, entropy coding, JPEG-2000 characteristics


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


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


Material Resource Management concepts

QoS and resources, establishment phase and transmission/enforcement phase

Admission control of resources, reservation and allocation of resources

Negotiation Protocols


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


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.


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


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


QUEUING , QUEUE MANAGEMENT AND RATE CONTROL


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)


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


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)


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


Class-based WFQ


PQ – Priority Queue

ERROR CONTROL: AVOIDANCE, DETECTION, CORRECTION


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.


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


Go-back-N Retransmission


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

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