Image and Sound Retrieval

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Transcript Image and Sound Retrieval

Interface Design
Session 11
LBSC 790 / INFM 718B
Building the Human-Computer Interface
• Questions
• Graphical interface design
• Auditory interface design
• Audio in Java
• Project updates
• Group things meaningfully
– Design in a natural task-oriented flow
– Use the corners
• Leverage consistency
– Similar things should look similar
– Different things should look different
• Encourage exploration
– Make it obvious which way to go
– Avoid hidden functions
• Strive for simplicity
– Use hierarchies judiciously to limit complexity
• Design for monochrome displays
– Provides assured access for color blind users
• Add muted colors where they help
– Useful for rapid recognition of categories
– Limit to 4 colors per screen (7 per application)
• Pay attention to readability
– “Similar” colors look different on another display
– Different systems may have different defaults
• Don’t make icons too small
– Fitts’ Law: Time = f(distance, size)
• Size can be used to illustrate quantity
– Scale size coding by at least 1.5
• No more than 4 font sizes
• Drill down
– Mouseover tool tips, menu expansion
• Illustration
– Change over time, icon behavior (on mouseover)
• Display space reuse
– Ticker tape, slide show
• Visible transitions
• 3-D visualization
– E-archivarius demo
• Attention management (once!)
Graphical Design Critique
• Select any 3 GUI’s you know and can use here
– e.g., Windows XP, Google, USMAI catalog
• Work in in groups of 3 to critique each
– Using IBM design guidelines
– What are the 3 best features of each?
– What are the 3 principal weaknesses of each?
Aural Perception
• We respond to sounds without prior focus
– Lack of focus limits simultaneous stimuli
• Absolute amplitude & pitch hard to interpret
– But changes stand out clearly
• Stereo effect provides a sense of direction
– Relative amplitude, phase difference
Auditory Display
• Nonspeech audio output for user interfaces
• Same objectives as graphical output:
– Alert the user to exceptional conditions
– Provide ubiquitous feedback
– Present information
• But different characteristics
– Effective even without focus
– Fairly low resolution
Auditory Display Design
• Need a metaphor
– Clock ticking, alarm bells, keyboard clicks, etc.
• Channel is easily overloaded
– Focus helps manage cognative load
• Changes are more useful than values
– Pitch, amplitude, position, harmonics, etc.
An Auditory Image Display
• Display 2-D images using only sound
– Sweep from left to right every second
• Audible pause and click between sweeps
– Top pixels are high frequency, bottom are low
• Blind users can detect objects and motion
– Time indicates horizontal position
– Pitch indicates vertical position
– Sweep-to-sweep differences indicate motion
Encoding Audio
• Number of channels
– 1 for mono, 2 for stereo [typically interleaved]
• Samples per second [per channel]
– 44,100 for CD; 8,000 for (wireline) telephones
• Bits per sample and quantization technique
– 16-bit linear (“pcm”) [signed or unsigned] for music
• In normal or swapped (“little-endian”) byte order
– 8-bit logarithmic (“mu-law”) for speech
• Header format
Common Audio File Types
• Audio files are headers followed by data
– File type specified data format
• .au (Unix)
– Big-endian, often 8-but mu-law
• .wav (Microsoft)
– Little-endian, often 16-bit pcm
• .aiff (Apple)
– Big-endian, less often used
• .raw (headerless)
– Requires the user to configure parameters
Playing Audio in an Applet
• All applets have an AudioClip class
– Handles only one format (8-bit mu-law mono .au)
• import java.applet.*
• Obtain the audio file from the server
clip= getAudioClip(getDocumentBase(), fileName)
• Play the clip
– plays it once
– clip.loop() repeats until clip.stop() is invoked
Playing Audio with Java Sound
• Import javax.sound.sampled.*
• Open the file (must be .au, .wav or .aiff)
audio = AudioSystem.getAudioStream(fileName);
• Determine the encoding
format = audio.getFormat();
• Set up audio output for that format
line = AudioSystem.getLine(format); [roughly…]
• Copy bytes from the file to the audio output
• Examples are available
Audio in the Java Media Framework
• Additional file types
– .avi, .mpg, .mp3, .mov
• Includes support for streaming audio
– RealPlayer SDK includes JMF Classes
• Allows synchronization with other media
– Video and MIDI music
• Requires a separate download
Playing Audio using JMF
• import*;
• Create the media player bean
MediaPlayer mp=new MediaPlayer();
• Load a file
• Play the file
– mp.start();
– mp.stop();
Putting It All Together