Saving bitrate vs users where is the break even point in mobile video quality
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Saving Bitrate vs. Users: Where is the Break-Even Point in Mobile Video Quality?. ACM MM’11 Presenter: Piggy Date: 2012.05.07. Outline. Introduction Related Work User Study Result Discussion and Conclusion. Introduction. Mobile video service is getting popular

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Saving bitrate vs users where is the break even point in mobile video quality

Saving Bitrate vs. Users: Where is the Break-Even Point in Mobile Video Quality?

ACM MM’11

Presenter: Piggy

Date: 2012.05.07


Outline

Outline

  • Introduction

  • Related Work

  • User Study

  • Result

  • Discussion and Conclusion


Introduction

Introduction

  • Mobile video service is getting popular

    • Due to the development of mobile device

  • Minimizing video bitrate is important

    • Wireless networks prefer low bitrate to adapt to different bandwidth conditions

    • Users prefer low bitrate as most network providers normally charge for data usage

    • Video providers need to save costs associated with serving the content


Introduction1

Introduction

  • However……

    • Low video bitrate => poor video quality

  • Fortunately……

    • Nonlinear relationship between perceived quality and video bitrate


Introduction2

Introduction

  • Goal: To find the most efficient bitrate requirement that

    • Optimizes bandwidth usage

    • Maintains good user viewing experience

  • Lowest acceptable video quality vs. lowest quality for long term viewing


Introduction3

Introduction

  • Contribution

    • Mapping of video bitrates to the subjective judgment of quality pleasantness

    • Impact of content type, video encoding parameters and user profile on mobile video viewing experience

    • Users’ selection processes and their criteria for the lowest pleasing quality for different content type


Related work

Related Work

  • Users’ requirements for mobile video depends on

    • Social and psychological factors

      • Consumption model, service, user profile, context, etc…

    • Video quality

      • Spatial and temporal resolution

      • Quantization

      • Motion and texture complexity


Related work1

Related Work

  • Factors influence the reduction of bitrate

    • Resolution

    • Frame rate

    • Quantization

  • And the degradation in perceived video quality is not proportionate to the decrease in bitrate


Related work2

Related Work

  • Subjective assessment

    • ITU recommendation: scale-based subjective assessment

      • 5/9/11-sclaes

      • Overburdens participants

    • Binary choice method for assessing acceptability


Related work3

Related Work

  • Though previous works have identified the lowest acceptable quality level

    • They were restricted by the technology and device at that time.

    • Different resolution

    • People behaviors have changed (got used to HD quality)


User study

User Study

  • Equipment

    • iPhone 3GS with 16GB storage

    • Display: 480x320 pixels

    • H.264/AVC

      • Up to 1.5 Mbps, 640x480 pixels, and 30 frames per second

    • AAC-LC audio format

      • Up to 150 kbps, 48kHz


User study1

User Study

  • Test material - 5 content types

    • News, music, animation, sports and movie


User study2

User Study

  • Test material – encoding using 3 parameters

    • Quantization parameters (QP)

    • Spatial resolution (SR)

      • 320x240, 480x320, and 640x480

    • Frame rate (FR)

  • Divided into 3 groups based on SR:L, M and H with each group contain 10 test clips

    • 30 test clips for each content type


User study3

User Study

  • Total 150 test clips

    • 30x5


User study4

User Study

  • Participants

    • Lounge area outside of a university library

    • 40 participants

      • Equal number of males and females

      • Age range: 17 ~ 35 (average = 23.2)

  • User profile collection

    • Experience of using mobile video

    • Preference for content types


User study5

User Study

  • Participants’ profile


User study6

User Study

  • Procedure

    • Scenario explanation

    • 3 steps within 20-25 mins for data collection

      • Participant’s profile collection

      • Participant randomly chose the video contents

      • A short interview


User study7

User Study

  • Customized iPhone application

    • Participant profile collection

    • Content type choice

    • History review

    • Quality adjustment

      • Ascending

      • Descending


User study8

User Study


User study9

User Study


User study10

User Study

  • Interview

    • What criteria did you use to select the desired video quality?

    • Is there any difference between your criteria for different content type? Why?


Result

Result

  • Acceptability calculation

    • Lower than the selected lowest acceptable clip => 0

    • Otherwise => 1

    • Refers to the percentage of participants accepting a video quality as the lowest quality

  • Binary Logistic Regression

    • Video encoding parameters

    • Content type

    • Viewing order

    • User profile


Acceptability and encoding parameters

Acceptability and Encoding Parameters

  • Different from

    • Content to content

    • Resolution to resolution

  • Movie is the lowest while new is the highest

  • The difference reduces as the resolution increases


Acceptability and encoding parameters1

Acceptability and Encoding Parameters


Acceptability and encoding parameters2

Acceptability and Encoding Parameters

  • Acceptability group

    • 0 – 40% should be avoided

    • 41 – 60% critical state

    • 61 – 80% can please users

    • 81 – 100% high user satisfaction


Acceptability and encoding parameters3

Acceptability and Encoding Parameters

  • Bitrate-acceptability curves


Acceptability and encoding parameters4

Acceptability and Encoding Parameters

  • Bitrate-acceptability curves


Acceptability and encoding parameters5

Acceptability and Encoding Parameters

  • Bitrate-acceptability curves

    • High resolution needs a higher bitrate

    • The acceptability of “sport” rises slower than other content types

    • Mapping of bitrate to acceptability


Influencing factors on quality acceptability

Influencing factors on quality Acceptability

  • Significant factors

    • Quantization parameter

    • Spatial resolution

    • Frame rate

    • Content type

    • Gender

    • Frequency

    • Duration

    • Viewing order

  • Non-significant factors

    • Age


Influencing factors on quality acceptability1

Influencing factors on quality Acceptability

  • Effect of content type

    • Movie vs. music, news, and animation

    • Spatial resolution decreases => content type more significant

  • Effect of encoding parameters

    • Video quality increases with

      • Decrease of QP (great difference among adjacent QP values)

      • Increase of SR

      • Increase of FR


Influencing factors on quality acceptability2

Influencing factors on quality Acceptability

  • Effect of viewing order

    • Acceptability in descending order is lower than ascending order

    • Significant for animation, music, news and sports but not for movie


Influencing factors on quality acceptability3

Influencing factors on quality Acceptability

  • Effect of user profile


Influencing factors on quality acceptability4

Influencing factors on quality Acceptability

  • Effect of user profile

    • Gender vs. frequency


Influencing factors on quality acceptability5

Influencing factors on quality Acceptability

  • Effect of user profile

    • duration vs. frequency


Influencing factors on quality acceptability6

Influencing factors on quality Acceptability

  • Effect of user profile

    • Users’ preference


Quality selection patterns

Quality selection patterns

  • Average time spent on switching is different from content type to content type

    • News is the lowest


Quality selection patterns1

Quality selection patterns

  • Two selection patterns

    • Directly choose the target qualities without hesitation – mostly in ascending order

    • Bounced to and from the lower of higher quality for comparison – mostly in descending order


Criteria of acceptability quality

Criteria of acceptability quality

  • Users have different assessment criteria for different content types

    • Movie – high quality required (HD quality)

    • News – audio quality and sync.

    • Music – audio quality

    • Animation – fewer requirement

    • Sport – higher quality needed when small objects appear

  • Users’ preference leads to different result on the same content type

    • Ex: sport and news


Discussion and conclusion

Discussion and Conclusion

  • Users’ profile matters

  • The result is different from previous works

  • Exact required bitrate still depends on individual video, here only gives a estimated range

  • Platform dependency as well as video codecs

  • Fixed vs. adjustable service?

  • Prediction model and optimal delivery strategy


The end

The End

  • Thanks for your attention


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