Dr. Charles Krasic*, Anirban Sinha* and Lowell Kirsh**

Dr. Charles Krasic*, Anirban Sinha* and Lowell Kirsh**

* University of British Columbia, Vancouver, Canada.** Amazon Inc, Seattle, USA.

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MotivationMultimedia capable networked devices are

heterogeneous – from powerful desktops to resource constricted mobile devices.

In a single device, in addition to overall capabilities, there can be competition for resource sharing between various applications.

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Motivation (Contd ...)Streaming media must be able to scale to the

diversity of available hardware as well as time varying nature of available resources.

Priority-Progress Streaming is a method for bandwidth-adaptive streaming.

This paper: apply the same basic Priority-Progress concepts toward making “CPU-adaptive” applications.

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CPU Burstiness of Video

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The ProblemCPU requirements for a single video often

vary greatly over the time, in correlation with bitrate.

Device diversity and resource dynamics make over provisioning impractical.

We need a mechanism for graceful adaptation hopefully maximizing quality (hence CPU) utilization – its tough!

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Adaptation Performance of Popular Video Applications

We take VLC and MPlayer and instrument them to measure their temporal fidelity – measured using two matrices:

Jitter – time delta between successive frame displays, captures visible playback stoppage.

FPS - idea of overall smoothness of video.

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Adaptation Performance of Popular Video Applications(Contd ...)We play N simultaneous videos (all same

video), in each of VLC and MPlayer for N = 2 to 6

We select two values of N; Nsat that just saturates the CPU and N2 x sat which is twice the value of Nsat.

Both VLC and MPlayer have some capability to adapt to higher CPU loads; viz. through dropping of frames.

We expect adaptation to occur in N2xsat case.For both players, we found Nsat = 3 and thus

N2 x sat = 6

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VLC & MPlayer in underload

(a) VLC in underload for one single video

Total 3 videos (typical case for all videos)

(b) MPlayer in underload for one single video

Total 3 videos (typical case for all videos)

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VLC and MPlayer in Underload – Summary

In under load, all players perform well; MPlayer requires 14% less CPU than VLC.

Jitter in underload is uninteresting because with FPS = 24 and no frame dropping, basic jitter is approximately 41.7 ms in all cases.

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VLC & MPlayer in Overload – FPS and Jitter for a single video

(a) VLC in overload (one player out of 6)

(b) MPlayer in overoad (one player out of 6)

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VLC & MPlayer in Overload – Fairness across videos

(a) VLC in overload – All videos

(b) MPlayer in overoad – All videos

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VLC & MPlayer in Overload – SummaryMPlayer exhibits bimodal fairness with some

videos experiencing almost full frame rate and others experiencing very low frame rate.

Overall MPlayer shows greater consistency towards frame dropping.

Fairness for VLC across all videos is very poor.

We suspect the differences between MPlayer and VLC as partly due to their architectural differences – VLC is multithreaded whereas MPlayer is event driven.

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Priority-Progress Decoding

In this paper, we design, implement and evaluate Priority-Progress Decodingderives from our previous work on bandwidth-

adaptive streamingPriority-Progress Streaming

Sclalable Video codec, our variant of MPEG-4, called SPEG4

Priority Mapper, translates declarative policies and raw video into appropriately prioritized ADUs

Priority-Progress, adaptive streaming algorithm/protocol

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Declarative Adaptation Policy Specification

specify preferences instead of actions

Specifications consists of a set of utility functions, one per quality dimension

Mapper transforms policy specs into an executable adaptation strategy

A streaming mechanism executes the adaptation

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0

Quality Loss

Util

ity

As good as

Perfect

Useless

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Priority-Progress Adaptation

Take prioritized layered application data (SPEG + mapper), and apply adapation windowin original PPS, window did not slide, it does in

PPDbefore resource constraint (Network, or CPU)

take video with window boundaries (time based) re-order from original (time) order to priority order on completion of each step, re-order data into time

order if time runs out, drop remaining low-priority data

Ongoing work: “window scaling”, spatial quality

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QStream Performance with equal Utility Specification

(a) QStream in underload (4 videos)

(b) QStream in overload (8 videos)

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QStream Performance with Preferential Utility Function Specified for Selected Video

(a) QStream in underload (4 videos)

(b) QStream in overload (8 videos, 1 boosted in

importance) 17

QStream Jitter in Overload and Underload.

(a) QStream in underload (4 videos)

(b) QStream in overload (8 videos)

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QStream Results – SummaryQStream adapts gracefully and uniformly to

increased CPU load across all videos. Jitter even in overload is reasonable and

uniform and proportional to the number of frames dropped.

QStream allows relative importance of streams to be specified; allowing control over quality—regardless of complex resource implications.

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QuestionsI am representing my supervisor Dr. Krasic

who was supposed to present the work.I will try as best as I can to answer all your

questions.For further information, please contact Dr.

Krasic:

krasic@cs.ubc.cahttp://qstream.org

(all benchmark scripts and qstream source available open source)

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