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Thesis Defense Olufunke Olaleye. Symbiotic Audio Communication on Interactive Transport. Technology Overview. Today's Internet traffic contains both audio and data packets. Sensitive traffic (audio) shares bandwidth with other non-sensitive traffic as shown fig 1.1 VoIP Audio Chat

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thesis defense olufunke olaleye
Thesis Defense

Olufunke Olaleye

Symbiotic Audio Communication

on

Interactive Transport

technology overview
Technology Overview
  • Today's Internet traffic contains both audio and data packets.
  • Sensitive traffic (audio) shares bandwidth with other non-sensitive traffic as shown fig 1.1
    • VoIP
    • Audio Chat
    • Online Radio
    • Real time internet lecture
    • Real time Internet conference
    • Online Music service
    • Internet News

Figure 1.1 Bandwidth Limited Network

Symbiotic Audio Communication on Interactive Transport

growth of audio
Growth of Audio

While, the technology has moved many businesses online, the use of audio traffic over the Internet has growth exponentially.

  • However, audio perception is highly susceptible to disturbance in temporal quality.
  • Packet loss, delay and jitter affects quality of service during congestion.
  • To maximize the audio/voice quality, some algorithms proposed to adapt:
  • Size of the playout buffer
  • Coding rate
  • Packet path diversity [25]
  • Challenge Receiving feedback from the network about congestion.

Source: Infonetics Research, February 2006

Symbiotic Audio Communication on Interactive Transport

research goal of thesis
Research Goal of Thesis
  • A well-engineered, end-to-end network is necessary to transmit audio over the Internet.
  • Goal of this thesis:
  • Reduce the delay and jitter faced by audio traffic in the network during congestion.
  • An efficient solution: Sender’s end (encoder) ability to sense the state of the network and react accordingly.
  • R &D:
  • Developed symbiotic perceptual audio streaming mechanism that is capable of detecting the underlying bandwidth of the network and modify the target bit rate to suit the network condition.
  • Combines the quantization technique to accurately represent the audio signals without distortion.
  • Proposed TCP Interactive (iTCP)
  • --- Operationally state equivalent to the conventional TCP except applications.
  • --- Optionally subscribe and receive selected local end-point protocol events in real-time.

Symbiotic Audio Communication on Interactive Transport

the human auditory perception
The Human Auditory Perception
  • Human ear perceives signal within the range 20 and 20000 Hz.
  • High sensitivity is between 2.5 and 5 kHz and decreases beyond and below this frequency band.
  • Two Principle Perception is based on
    • Threshold in quiet --- Sensitivity.
    • Masking threshold ---
      • Temporal
      • Simultaneous masking
  • Human auditory system perceives signal in a non-equal width sub-band called critical bands, it’s unit is barks

Figure 2.2 Threshold in quiet and masking threshold

Symbiotic Audio Communication on Interactive Transport

impact of threshold in quiet
Impact of Threshold in Quiet

Threshold in Quiet

Quantized values without adaptation

  • Signal strength below the threshold in quiet are inaudible to the human ear.

Quantized values with 25% adaptation

Symbiotic Audio Communication on Interactive Transport

impact of masking threshold
Impact of Masking Threshold

Quantizes value with a single masker – 37.5%

Quantized values with multiple maskers ---50%

Final Output

Symbiotic Audio Communication on Interactive Transport

effect of simultaneous temporal masking
Effect of Simultaneous & Temporal Masking
  • Masking threshold ---
    • Temporal
    • Simultaneous masking

Symbiotic Audio Communication on Interactive Transport

audio adaptation
Audio Adaptation
  • Audio signal simultaneously passes though the hybrid filter bank and psychoacoustic model.
    • The hybrid filter bank
      • Divides the input signal into chucks of 576 samples called granule and sub bands of frequency.
      • Provides a specified mapping in time and frequency.
  • The psychoacoustic model behaves like the human auditory system.
    • Computes a just noticeable noise level in each subband.
    • Determines the block (window) type --- (short/long).
      • Computes the energy in each partitions band (threshold calculation partition).
      • Convolves the partitioned energy by applying the spreading function (frequency spread of masking).
      • Apply pre-echo control using some constants (2 or 16).
        • Compares the threshold with the last threshold and quiet threshold and takes the maximum.
      • Converts threshold calculation partition to scalefactor bands and calculates the signal to mask ratio.

Figure 2.5 Block Diagram of the encoder

Symbiotic Audio Communication on Interactive Transport

tables for threshold calculation partitions
Tables for Threshold calculation partitions

Threshold calculation partitions is computed with following parameters: width, minval, threshold in quiet, norm and bval:

(44.1kHz sampling rate---long)

(44.1kHz sampling rate---short)

Parameters for computing the SNR, for short window, it is read from a table.

Norm is normaling constant for each sub band

Bval is bark value.

For low freq, the strength of the masking is limited by minval

bark: a non-linear frequency scale.

Symbiotic Audio Communication on Interactive Transport

tables for converting threshold calculation partitions to scalefactor bands
Tables for converting threshold calculation partitions to scalefactor bands

There are 21 bands at each sampling frequency for long windows and 12 bands each for short windows.

(44.1kHz sampling rate---long)

(44.1kHz sampling rate---short)

  • The number of partitions (cbw) converted to one
  • scalefactor band (excluding the first and the last partition).
  • The threshold calculation partitions are converted directly to scalefactor bands. The first partition which is added to the scalefactor band is weighted with w1, the last with w2
  • bo is the first index value of cbw
  • bu is the last index value of cbw

Symbiotic Audio Communication on Interactive Transport

audio adaptation1
Audio Adaptation

The noise allocation block

  • Uses the output of the psychoacoustic model, “signal to mask” ratio.
  • Used the noise level in noise allocation to determine the actual quantizers and quantizer levels.
  • Determines how to allocate the number of code available for quantization of subband signals.

The spectrum (frequencies) are broken into "scalefactor bands".

Thes bands are determined by the MPEG ISO spec.

In the noise shaping/quantization code, we allocate bits among the partition bands to achieve the best possible quality

  • It uses two nested iteration loops.
    • Distortion control loop (outer loop)
    • Rate control loop – (inner loop)
      • The inner loop quantizes the input signal and increases the quantizer step size until the output can be coded with the available amount of bit.
      • After completion of the inner loop, an outer loop checks the distortion of each scalefactor band, if the allowed distortion is exceeded, it amplifies the scalefactor band and calls the inner loop again.

quantize in an iterative process

Symbiotic Audio Communication on Interactive Transport

audio adaptation2
Audio Adaptation
  • If the overall bit sum is less than the available bits to encode a frame.
  • The best quantized values are coded by Huffman coding to further reduce their space requirement.
  • The bitstream formatting block assembles and formats quantized subband signal using Huffman code and other side information into bitstream.
  • This is then passed into the network for transmission.

Symbiotic Audio Communication on Interactive Transport

tcp congestion control
TCP Congestion Control
  • TCP provides a connection-oriented, reliable delivery of data streams between two applications or hosts
  • TCP uses two mechanism to detect network congestion
    • Retransmission timer time out.
    • Duplicate ACKs.
  • Congestion Control Algorithms
  • Slow-start and congestion- avoidance.
  • Fast-retransmit and fast-recovery.

Figure 3.1 Slow Start/Congestion Avoidance (SSCA) mechanism.

Figure 3.2 Fast Retransmit/Fast Recovery (FRFR) mechanism

Symbiotic Audio Communication on Interactive Transport

tcp congestion control internal events
TCP Congestion Control Internal Events

Subscribable

Events

}

Table 3.1. TCP Congestion Control Internal Events

  • In this thesis, for simplicity, we use event 1, retransmission timer time out.

Symbiotic Audio Communication on Interactive Transport

itcp interactive tcp
iTCP: interactive TCP
  • An application that has subscribed to the kernel also binds a T-ware to a selected TCP event through the subscription API as shown by line 1 and 2 of figure 4.
  • When the TCP state changes as a result of congestion in the network, it also causes an event to occur in the TCP kernel.
  • The event monitor is aware of the changes that occurred; thus, it responds instantly by sending a signal in (3a) to the signal handler and also stores the event information in (3b).
  • The signal handler catches the signal from the kernel and requests the event type (4a, 4b) from the kernel via the probing API.
  • The appropriate T- Transientware Modules (or T-ware) (5) is triggered to serve the particular event.

User Space

7

Application

T-ware

[ 1 ]

T-ware

[ 2 ]

T-ware

[ n ]

1

5

6a

TCP Connection

Signal Handler

4a

System

Socket

API

Subscription

API

Probing API

3a

2

6b

TCP Kernel

4b

3b

Connection State

Event

Monitor

Event

Information

Figure 4. The iTCP extension and API.

Symbiotic Audio Communication on Interactive Transport

symbiosis throttling model
Symbiosis Throttling Model
  • During congestion, detected by the time-out event ( ζ = 1 ), the model reduces the target bit rate to considerable lesser or minimum rate.
  • bmax, target bitrate at a normal state
  • bmin, the minimum acceptable rate
  • Reduction ratio = rate retraction ratio

= ρ = b min/ bmax (5.1)

  • “Running generation threshold” function = link between the underlying TCP and the model.
  • (5.2)

Figure 5.1 Symbiosis throttling Model (Input Rate)

Figure 5.2 Symbiosis throttling Model (Output Rate)

Symbiotic Audio Communication on Interactive Transport

symbiosis throttling model1
Symbiosis Throttling Model
  • Running control generation function” b(t) =

(5.3)

  • Rs = reservoir size
  • Estimated Target Buffer Fullness
  • (5.4)

(5.5)

  • A = Actual number of bits per granule

Figure 5.1 Symbiosis throttling Model (Input Rate)

Figure 5.2 Symbiosis throttling Model (Output Rate)

Symbiotic Audio Communication on Interactive Transport

symbiosis throttling model2
Symbiosis Throttling Model

Input Source audio

T-ware

Event

xr

xr

b

Reservoir

b (t), ρ

Perceptual Model

Rs

ratio(sb)

T

Noise Allocation

Estimated Target

Buffer Fullness

Compute Allowed

Distortion

T (t), xr

0.9 * T

, Rs

xmin(sb)

0.9 * T (t), Rs

Amplify violated

masking threshold

xfsf(sb)

Compute

Distortion in

Quantization

ix

Quantization of

actual energy

xr  ix

(xmin – xfsf) of scalefactor band j < 0

violated

ok

xr (i) = xr (i) * ifqstep

xfsf(sb)

Quant Compare

Compute

Distortion in

Quantization

ix

Quantization of

amplified energy

xr  ix

Code

Information

Rs

  • The best quantization with allowed distortion to sharp the noise.

Output audio stream

ifqstep = sqrt(2) ^ ((1 + scalefac_scale) * ifq(scalefactor band))

Symbiotic Audio Communication on Interactive Transport

symbiosis mechanism the t ware
Symbiosis Mechanism: The T-ware
  • Signal handler
  • Catch the signal from the kernel
  • and invoke the appropriate T­ware.
  • Encoder subscribe with the
  • “retransmit timer out" event only.
  • The mechanism use to reduce delay is called T-ware.
  • It gives the transport layer the ability to communicate with the application layer (encoder).
  • The key element is the loss event handler that generates a signal.
  • The signal information is used to probe iTCP service.
  • Couple with the retraction ratio ρ , the rate is reduced to achieve the objective of the thesis.
  • T-ware calculates a frugal
  • state target bitrate base
  • on the retraction ratio
  • Stores the reduced rate
  • in the “rate.par” file.
  • Recovery-T-ware
  • The recovery T-ware kicks in at the
  • Trecovery time
  • Returns the encoder bit rate to
  • normal rate.

Figure 6a & 6b Pseudo code of the Signal Handler and the Recovery handler

Symbiotic Audio Communication on Interactive Transport

experiment set up
Experiment Set Up

Figure 7.1 Experiment setup

Symbiotic Audio Communication on Interactive Transport

experiment test samples
Experiment (Test Samples)

TEST ( 3 types of audio sound quality)

  • High quality music (HighQmusic),
  • Low or Poor quality music (LowQmusic)
  • Speech mixed with music (SpeechMusic)

3 Running Mode

  • iEXP
  • iOFF
  • Classic

Table 7.1 Experiment control flags and running modes

Symbiotic Audio Communication on Interactive Transport

experiment and performance analysis
Experiment and Performance Analysis
  • The parameters used in the experiments:
  • (i) Predetermined rate retraction ratio ( ρ = 0.50)
  • (ii) Bit rate
  • To compute b(t), the rate retraction ratio is multiplied by the current bit rate. (Bit rate * ρ )
  • Frames information are collected for the first 800 up to 1200 audio frames of the encoder and the player.

Symbiotic Audio Communication on Interactive Transport

performance analysis
Performance Analysis
  • Performance of iEXP is better than the classic TCP.
  • The delay buildup in Classic and iOFF are much higher than that experienced by the iEXP (iTCP) as indicated by the step jump.
  • The step jump of iEXP is much smaller as a result of the rate retraction ρ
  • iEXP was able to recover from delay buildup in few seconds compare to the Classic and iOFF.

Figure 7.2. Frame arrival delay on the three audio qualities

Symbiotic Audio Communication on Interactive Transport

performance analysis1
Performance Analysis
  • Assuming a packet arrives at the receiver end at time tj
  • Expected arrival time for the packet is ej.
  • Referential jitter (refJitter(j)) = (tj - ej)
  • refjitter(j) is negative if packet j arrives early at the receiver end.
    • It can be buffered and played at the actual time.
  • refjitter(j) is positive, if packet j has arrived late at the receiver end.
    • The player will pause and wait for packet that arrive late.
  • The higher the delay, the higher the jitter experience by the frames.
  • The step jumps in the iEXP were much smaller than those in TCP-classic and iOFF.
  • Furthermore, this indicates that the interactive TCP reduces jitter.

Figure 8.3. Referential Jitter on the three audio qualities

Symbiotic Audio Communication on Interactive Transport

performance analysis2
Performance Analysis
  • Symbiotic rate reduction that occurred as a result of the rate modification between the rate controller of the encoder and the symbiosis unit
  • Target bits and the actual bits generated by the encoder for each frame.
  • The rate retraction ratio of the symbiosis kicks in when a time out event is triggered and reported by iTCP during congestion.
  • The effect is observed on the plots as number of bits drop in accordance with the rate retraction ratio.

Figure 7.4. Symbiotic Rate Reduction on the three audio qualities

Symbiotic Audio Communication on Interactive Transport

performance analysis3
Performance Analysis
  • Comparison of frame delay and acceptance ratio
  • A delay tolerance of d = 2, 4, and 6 seconds are introduced to measure the average frame delay and acceptance ratio.
  • iEXP mode experience a low delay and high acceptance ratio.
  • iTCP’s T-ware mechanism allowed the application to use sophisticated techniques to control the temporal qualities of its traffic.

Table 7.2 Average Frame Delay and acceptance ratio

Low delay & High acceptance ratio.

Symbiotic Audio Communication on Interactive Transport

performance analysis4
Performance Analysis
  • Overall stream compression
  • The overall delivery bits in the iEXP mode reduce to 80 – 90% of the original bits
  • iOFF and Classic cases shows no adaptation.
  • The file size of iEXP mode reduce significantly compared to the other modes.
  • The audio quality between the sending end and the receiving end is achieved perceptually by the temporal and spectral resolution.
  • iTCP provides a means of tradeoff of terrible frame delay for a satisfactory reduction of quality.

Table 7.3 Percentage of total bits delivered for each mode

Table 7.4 Sizes of the audio files

Symbiotic Audio Communication on Interactive Transport

performance analysis5
Performance Analysis
  • Aim of the iOFF mode --- Study the overhead introduced by the event notification service.
  • Increase total transmission time for all modes.
  • iOFF mode is higher than the classic TCP mode due to event notification service enabled.
  • iEXP mode is much smaller than the other modes
    • Indicates the application level performance outweighs the overhead.

Figure 7.5 Overhead of the interactivity service

Symbiotic Audio Communication on Interactive Transport

conclusions
Conclusions
  • Aim: Reduce delay and jitter of audio traffic.
  • Solution: Design an interactive and friendly application that receives the state feedback from the network – Symbiotic encoder.
  • Achievements: Dynamic reduction of jitter and delay of time sensitive traffic during congestion.
          • Network congestion reduction by reducing the traffic at the source.
          • Trade off quality for delay and jitter.
          • The approach is simple and does not alter any network dynamic to be optimal (e.g fair queuing).
          • Its effect is entirely on the application layer.
          • It also further validates interactive transport control protocol (iTCP) usefulness and the efficiency through the idea of the event notification.
  • Technically, this scheme is not applicable to non-elastic traffic such as simple file transfer.

Symbiotic Audio Communication on Interactive Transport

future work
Future Work
  • Optimization: The parameters in the scheme are user defined but can be optimized with the symbiotic throttling model in [13].

The experiment can be performed using the other subsribable events(i.e. duplicate ACK).

Symbiotic Audio Communication on Interactive Transport

biblogrphy

[1] Andersen D., Bansal D., Curtis D., Seshan S., and Balakrishnan H., "System Support for Bandwidth Management and Content Adaptation in Internet Applications," Proc. of OSDI'OO, Oct. 2000, San Diego, CA

[2] Balakrishnan H., Rahul H., and Seshan S., "An Integrated Congestion Management Architecture for Internet Hosts," Proc. of ACM SIGCOMM, Cambridge, MA, Sep 1999. pp.115-187.

[3] Catherine Boutremans, Jean-Yve L Boudec, “Adaptive Joint Playout Buffer and FEC adjustment for the Internet Telephony,” 2003.

[4] Eitan Altman, Chadi Barakat, Victor Ramos, “Queuing Analysis of Simple FEC schemes for IP Telephony,” 2001.

[5] Floyd S., Handley M., Padhye J., and Widmer J.,“Equation-Based Congestion Control for Unicast Applications,” August 2000. SIGCOMM 2000

[6] H. Schulzrinne, S. Casner, R. Frederick, and V. Jacobson, “RTP: A transport protocol for real-time applications,” RFC 1889, 1996

[7] Handley M., Floyd S., Pahdye J., and Widmer J., “TCP Friendly Rate Control” (TFRC): Protocol

[8] ISO/IEC 11172-3. Information technology -- Coding of moving pictures and associated audio for digital storage media at up to about 1,5 Mbit/s -- Part 3

[9] J. Mahdavi and S. Floyd, “TCP-Friendly unicast rate-based flow control,” in Draft posted on end2end mailing list, January 1997, http://www.psc.edu/networking/papers/tcp%20friendly.html.

[10] Jacobson V. and Michael J. Karels, "Congestion Avoidance and Control," Computer Communication Review, vol. 18, no. 4, pp. 314-329, Aug. 1988.

[11] Jacobson V., "Modified TCP Congestion Avoidance Algorithm," end2end-interest mailing list, April 1990

[12] Johnny Matta, Christine Pepin, Khosrow Lashkari, Ravi Jain, “A source and channel rate adaptation algorithm for AMR in VoIP using E-model,” June 2003.

[13] Khan J. and Zaghal R., "Symbotic Rate adaptation for Time sensitive Elastic Traffic with Interactive Transport," Journal of Computer Networks, Elsevier Science, March. 2006.

BIBLOGRPHY

Symbiotic Audio Communication on Interactive Transport

biblogrphy cont d

[14] Khan J., Zaghal R., and Gu Q., "Rate Control in an MPEG-2 Video Rate Transcoder for Transport Feedback based Quality-Rate Tradeoff;" PV2002, Pittsburgh, P A, April 2002.

[15] Khan J., Zaghal R., and Gu Q., "Dynamic QoS Adaptation for Time Sensitive Traffic with Transientware," IASTED WOC'03, Banff; Canada, July 2003.

[16] Khan J. and Zaghal R., "Event Model and Application Programming Interface of TCP Interactive," Technical Report 'TR2003-02-02', Feb. 2003.

[17] N. Shacham and P.M Kenney, “Packet recovery in high-speed networks using coding and buffer management,” in Proc. IEEE Infocom 1999 .

[18] Pradhan P., Chiueh T. and Neogi A., “Aggregate TCP Congestion Control Using Multiple Network Probing,” Proc. Of the 20th International Conference on Distributing Systems, ICDCS 2000.

[19] Rishi Sinha, Christos Paradopoulos, Chris Kyriakakis, “Loss Concealment for Multi-channel streaming audio,” June 2003.

[20] Sisalem D. and Wolisz A., “Towards TCP-Friendly Adaptive Multimedia Applications Based on RTP,”

Proc. of the 4th IEEE Symposium on Computers and Communications, 1998.

[21] Stevens W. R., “TCP/IP Illustrated, Volume 1: The Protocols,” Addison-Wesley, 1994.

[22] Wang R., Yamada K., Sanadidi M. Y., and Gerla M.,“TCP with sender-side intelligence to handle dynamic, large, leaky pipes,” IEEE Journal on Selected Areas in Communications, 23(2):235-248, 2005.

[23] Wen-Tsai Liao, Janet J.C.Chen, Ming-Syan Chen Chen, “Adaptive Recovery Techniques for Real Time Audio Stream”

[24] Wenyu Jiang, Hening Schulzrinne, “VoIP: Comparision and optimatization of packet loss repair methods in VoIP perceived quality under bursty loss,” May 2002

[25] Yi J. Liang, Eckehard G. Steinbach, Bernd Girod, “Voice over IP: Real-time voice communication over the nternet using packet path diversity,” October 2001.

[26] TR2007-02-01 Test Audio Set: Symbiosis Audio Streaming with iTCP, Olufunke Olaleye and Javed I Khan, February 2007.

BIBLOGRPHY(cont’d)

Symbiotic Audio Communication on Interactive Transport

questions and comments
Questions and Comments

Symbiotic Audio Communication on Interactive Transport