Video in CSCW

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Video in CSCW

• Part IMichael Boyle
• Part IIMichael Rounding

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Part IVideo Mediated Communication

• Role of visual channel in collaboration
• Video-mediated communication technologies
• Opportunities and applications of VMC

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Role of Visual Channel

• Significance
• Function and operation of visual behaviours
• Technological requirements
• Consequences of inadequate support

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Significance of Visual Channel

• Principle means for navigation and orientation in
  our 3D physical world
• Hand-eye coordination and motor skills
• Principle means for experiencing our 3D physical
  world
• Other senses are limited
• Greatly inconvenienced if disabled

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Characteristics of Visual Channel

• Humans can only focus on small area
• Large peripheral visual cone
• Humans are adept at handling vast quantities of
  visual information
• Scanning, searching, reacting to changes
• Recognizing, classifying
• Predominantly diurnal creatures
• Large eyes eyebrows stereoscopic vision

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Uses of Visual Channel

• Infer much about people from visual information
• Gender, age, status
• Identity, background, personality
• Bulk of human knowledge encoded visually
• Arts, aesthetics, entertainment
• Communication

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Visible Behaviours

• Gaze
• Facial expressions
• Gestures
• Posture

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GazeFunction and Operation

• Indicates locus of interest, activity
• One generally looks at something when one talks
  about it or is about to use it
• Uses grounding, workspace awareness
• Signals affective state
• Interest, disposition, attitude, emotion
• Uses pre-interaction informal awareness,
  conversational awareness

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GazeFunction and Operation

• Conveys extremely subtle yet significant content
• Infer big meaning from even small physical
  changes
• Although important, not always observed
• Observed lt7 of conversation time
• Mutual gaze (eye contact) lt5 of time

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GazeTechnological Requirements

• Careful camera position
• Eyes must be fully visible, aperture at eye-level
• Large field of view
• See point of interest
• High image resolution
• Clearly see orientation, percieve minor
  variations
• High frame rate, low latency
• Smoothly convey rapid changes in real-time

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GazeConsequences of Inadequate Support

• Systemic miscommunication, misinterpretation if
  undiagnosed
• Requires extra effort to explicitly communicate
  signals, or disambiguate/repair miscommunication
• De-referencing focal points is tough!

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Facial ExpressionsFunction and Operation

• Involves whole of the face
• Eyes, eyebrows, forehead, mouth (especial lips
  and corners), cheeks, ears, nose
• Conveys affective information
• Blinks, winks, smiles, frowns, furrowed brows,
  wrinkled up nose, etc.
• Uses conversational awareness, disambiguate
  meaning of sensitive or easily-misinterpreted
  content

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Facial ExpressionsTechnological Requirements

• Tight audio/video synchronization
• Face must be in full view with high resolution
• Fast frame rate to capture winks, etc.

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Facial ExpressionsConsequences of Inadequate
Support

• If latencies are too high, then signals may come
  at inappropriate times
• If resolution too low, may not be able to clearly
  discern expression, adding to ambiguity
• Could lead to break-down of conversation if
  important expression miscommunicated

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GesturesFunction and Operation

• Uses mostly hands, fingers, and arms
• Position, orientation, movement
• Position relative to other parts of the body, or
  other objects in environment
• Rapid, generally small movements
• Context crucial for interpretation
• Silent, subtle, implicit long-distance
  communication

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GesturesClasses

• Pointing gestures
• Grounding de-reference deictic references
• Emblematic or iconic
• Convey content
• Useful when words dont come to mind
• Sometimes redundant
• Beats
• Convey emphasis

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GesturesTechnological Requirements

• Large field of view
• Full body must be visible
• High image fidelity
• Resolution, frame rate high enough to capture
  small, rapid motions
• Likelihood that there will be obstructions
• Fixed, mono-camera configuration insufficient

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GesturesConsequences of Inadequate Support

• Miscommunication, resulting in explicit
  communication
• Misinterpretation of gestures could lead to
  conversation breakdown
• Missed deictic references impairs workspace
  awareness
• Loss of personable content

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PostureFunction and Operation

• Consequence of work
• Involves whole body
• Particularly head, neck back, hips
• Position, relative orientation are cues to look
  for
• Communicates affective information
• Particularly availability informal awareness

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PostureTechnological Requirements

• Field of view
• Must capture whole body yet provide background
  for reference
• Fidelity doesnt need to be high

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PostureConsequences of Inadequate Support

• Incorrect assessment of availability during
  pre-interaction periods
• Unnecessary interruptions, missed opportunities
• Erroneous assessment of affective information
• Impact on smoothness, but likely not so terrible

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Visible BehavioursRecap

• Subtle yet significant, sometimes redundant
• Signal attitude, disambiguate meaning
• Valuable personable aspect
• Conflicting technological constraints
• People can get by without them, but interaction
  dynamics are fundamentally altered

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Part IVideo Mediated Communication

• Role of visual channel in collaboration
• VMC technologies
• Opportunities and applications of VMC

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A/V Infrastructure

• Cameras and displays
• Digital vs. analog
• Microphones and speakers
• Digital vs. analog
• Half-duplex vs. full-duplex
• Microphone arrays, environmental audio
• Noise, feedback, attenuation

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Network Infrastructure

• Medium
• Digital vs. analog
• Dial-up, ADSL, T1, wireless
• Quality of service (QoS) factors
• Bandwidth, latency, jitter, delivery guarantees
• Packet-switched vs. circuit-switched
• Broadcast/multicast vs. unicast

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Audio Software

• Properties sample size, rate, number of channels
• Compression PCM, µ-Law, ADPCM, GSM/CELP, MP3
• Buffer size transmission overhead vs. latency
• Filtering, mixing

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Video Software

• Lossy vs. lossless compression
• RLE (run-length encoding) lossless
• replace runs of same-coloured pixels with count
• JPEG lossy
• uses signal-processing techniques to change
  representation of image to bring out redudant
  aspects
• quantization throws away resolution in chroma
  channel not visible to human eye
• entropy (Huffman) coding on result

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Video Software

• Intraframe vs. interframe compression
• M-JPEG intraframe
• MPEG intraframe/interframe hybrid
• JPEG compress key frames
• Encode back and forward differences of non-key
  frames
• Decreases bandwidth, increases latency
• Quality bits-per-pixel

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Video Software

• Frame rate
• Frame size

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General Impact of Inadequacies

• Frame size, resolution, fidelity
• Subtle facial expressions, gaze not discernable
• Lost of critical eye contact
• Field of view
• Locus of attention not visible
• Parts of face, body used in expressions not
  visible

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General Impact of Inadequacies

• Frame rate
• Subtle changes lost
• Latency
• Cues come at inappropriate time
• A/V synchronization
• Reduces value of redundant encoding

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VMC TechnologyRecap

• Technology never perfect
• Bandwidth/quality trade-off
• Results
• Content communicated subtly and implicitly via
  visual channel must be communicated explicitly
  via some other channel, or lost altogether
• People adapt, but personability of FTF is lost

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Part IVideo Mediated Communication

• Role of visual channel in collaboration
• VMC technologies
• Opportunities and applications of VMC

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Opportunities and Applications

• Tele-presentation/distance learning
• Augmenting shared workspaces
• Supporting informal interaction
• Tele-presence and mediating contact
• Function, operation, example systems, and lessons
  learned

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Tele-presentation

• Presenter/audience with presentation matter
• Numerous configurations
• with/without local audience
• multiple participants at each remote site
• multiple presenters at same/different sites
• Formal
• Information dissemination applications

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Tele-presentation

• Example systems
• Forum
• Telep
• TV call-in show

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Tele-presentationLessons Learned

• Audience likes it
• Enables participation
• Integrates well with other work tasks
• Presenters not so favourable
• Value of back-channels
• Reduced local attendance
• Sub-conversations

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Augmented Shared Workspaces

• Coordinating activities in shared workspace
  requires communication channels
• E.g., text-chat or telephone
• Integrate shared workspace and shared
  communication channels to create a shared tasks
  environment
• Traditional meeting tasks

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Augmented Shared Workspaces

• Example systems
• Montage
• ClearBoard
• TeamWorkstation
• NetMeeting

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Augmented Shared WorkspacesLessons Learned

• Diminished priority of video relative to audio
• Call setup minimize time, provide sense of
  approach
• Requirements vary with task
• Critical mass
• Know your users

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Casual Interaction Support

• Promote social interactions of serendipitous
  nature
• Based on value of social interactions to
  productivity
• Seamless integration of distant sites into a
  signal interaction space
• Hope to overcome effect of distance on social
  interactions and collaboration

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Casual Interaction Support

• Example systems
• VideoWindow
• Vkitchen
• CRUISER

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Casual Interaction SupportLessons Learned

• Public reaction mixed
• Not 100 transparent technology still a barrier
  to forging new relationships
• Difficult to diagnose failures
• Requires extended installation/observation periods

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Tele-presence and mediating contact

• Video makes for a subtle, unobtrusive means of
  delivering tele-presence for accruing distributed
  informal awareness
• Easy, natural for people to capitalize on visual
  information to coordinate interactions

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Summary

• Role of visual channel in collaboration
• Technological foundations
• Opportunities for video in CSCW
• Challenges

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SummaryRole of Video

• Communication medium
• Coordination medium
• Regulation and mediation of interactivity
• Subtle, implicit
• Important, but not in the obvious ways
• Importance varies with task

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SummaryVideo Technologies

• Present technology not very robust
• Bandwidth/fidelity trade-off
• Issues latency, field of view
• Consequences of inadequate technology
• Vary from minor inconvenience to conversation
  breakdown
• Must understand when video is crucial
• Design should reflect this

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SummaryOpportunities

• Tele-presentation
• Meeting support
• Communication channel for shared work activities
• Casual interaction
• Mediating interaction

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SummaryChallenges

• Understanding where video succeeds and fails
• Success is not always obvious
• Some failures are inevitable
• Basic technological issues
• Deployment, ubiquity, acceptance, incorporation
• Social issues privacy, accountability