Programming

1
Programming

• Week 5
• LBSC 690
• Information Technology

2
Agenda

• Quiz
• Multimedia wrap-up
• Audio encoding
• Streaming and synchronizing
• Programming languages
• History and types
• Basics (data types, control structure, etc.)
• Web programming (JavaScript)

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Basic Audio Coding

• Sample at twice the highest frequency
• One or two bytes per sample
• Speech (0-4 kHz) requires 8 kB/s
• Standard telephone channel (1-byte samples)
• Music (0-22kHz) requires 88 kB/s
• Standard for CD-quality audio (2-byte samples)

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Speech Compression

• Opportunity
• Human voices vary in predictable ways
• Approach
• Predict whats next, then send only any
  corrections
• Standards
• Real audio can code speech in 6.5 kb/sec
• Demo at http//www.data-compression.com/speech.htm
  l
• Scroll down to near the bottom

5
How do MP3s work?

• Opportunity
• The human ear cannot hear all frequencies at
  once, all the time
• Approach
• Dont represent things that the human ear cannot
  hear

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Human Hearing Response
Experiment Put a person in a quiet room. Raise
level of 1kHz tone until just barely audible.
Vary the frequency and plot the results.
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Frequency Masking
Experiment Play 1kHz tone (masking tone) at
fixed level (60db). Play test tone at a different
level and raise level until just distinguishable.
Vary the frequency of the test tone and plot the
threshold when it becomes audible.
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Temporal Masking
If we hear a loud sound, then it stops, it takes
a while until we can hear a soft tone at about
the same frequency.
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Putting it all together

• Psychoacoustic compression
• Eliminate sounds below threshold of hearing
• Eliminate sounds that are frequency masked
• Eliminate sounds that are temporally masked
• Eliminate stereo information for low frequencies

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Transmission

• Download
• Transfer the whole file, then start replay
• Can be very slow for large files
• Streaming
• Play the file as it is received
• Also suitable for live broadcasts
• Requires a sufficiently fast connection

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The Last Mile

• Traditional modems
• 56 kb/sec modems really move 3 kB/sec
• Digital Subscriber Lines
• 384 kb/sec downloads (38 kB/sec)
• 128 kb/sec uploads (12 kB/sec)
• Cable modems
• 10 Mb/sec downloads (1 MB/sec)
• 256 kb/sec uploads (25kB/sec)

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Streaming Audio and Video

• Begins replay after only a portion received
• Buffer provides time to recover lost packets
• Interrupts replay when rebuffering

Media Sever
Buffer
Internet
13
Narrated PowerPoint

• Create your slides
• Slide Show -gt Record Narration
• Set microphone level
• Record the narration
• Slide transitions are automatically captured
• Narration plays automatically when displayed

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Adding Video to PowerPoint

• Insert-gtMovies and Sounds
• Movies from file (a .mpg file)
• Decide whether you want autostart
• If not, it starts when you click on it

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Synchronizing Multiple Media

• Scripting Languages
• Synchronized Multimedia Integration Language
  (SMIL)
• Custom applications
• Macromedia Flash
• Content representation standards
• MPEG 4

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SMILe

• W3C standard
• Player-specific extensions are common
• XML, with a structure similar to HTML
• ltsmilgt
• ltheadgt lt/headgt
• ltbodygt lt/bodygt
• lt/smilgt

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Elements in SMIL

• Window controls (in ltheadgt)
• Controlling layout ltregiongt, ltroot-layoutgt
• Timeline controls (in ltbodygt)
• Sequence control ltseqgt, ltexclgt, ltpargt
• Timing control ltbegingt, ltendgt, ltdurgt
• Content types (in ltbodygt)
• ltaudiogt, ltvideogt, ltimggt, ltrefgt

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SMIL Examples

• Implemented in RealOne Player
• Example
• http//www.umiacs.umd.edu/oard/teaching/690/fall0
  5/notes/4/media.html
• First, run the executable
• Then, view .smil file

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Software

• Software models aspects of reality
• Input and output represent the state of the world
• Software describes how the two are related
• Examples
• Ballistic computations
• Google
• Microsoft Word

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Types of Software

• Application programs (e.g., Powerpoint)
• What you normally think of as a program
• Compilers and interpreters
• Programs used to write other programs
• Operating system (e.g., Windows XP)
• Manages display, CPU, memory, disk, tape,
• Embedded program (e.g., BIOS)
• Permanent software inside some device

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Programming Languages

• Used to specify every detail of the model
• Special purpose
• Able to specify an entire class of models
• Spreadsheets (Excel, ...)
• Databases (Access, Oracle, ...)
• General purpose
• Able to specify any possible model
• JavaScript, Java, Perl, C, C, ...

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History of Programming

• Machine language
• Language that machine can understand
• Assembly language
• Assembler changes names to machine code
• High-level languages
• Compiler/Interpreter translates to machine
  language
• FORTRAN, COBOL, C, C, Javascript
• Visual programming language
• Visually arrange the interface components
• Visual Basic,

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Machine Language

• Everything is a binary number
• Operations
• Data
• For instance
• 00001000 ADD
• 00010101 first number (21)
• 01010110 second number (86)

00001000 00010101 01010110
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Assembly Language

• Symbolic instruction codes and addresses
• Symbolic instruction code ADD
• Symbolic address SUM1
• For instance

ADD 21, SUM1
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High level Languages

• Procedural (modular) Programming
• Group instructions into meaningful abstractions
• C, Pascal, Perl
• Object oriented programming
• Group data and methods into objects
• Naturally represents the world around us
• C, Java, JavaScript

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Object Models

• Represent things in the world as objects
• Simplest objects are variables
• Represented with a name (n, teacher, )
• May be assigned a value (n4, teacherDoug, )
• Represent actions with methods
• Simplest methods are operations
• Represented with a symbol (, -, , /, , )
• Classes group objects with methods
• Models how kinds of things behave
• Objects are instances of classes

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Basic Data Types

• Boolean true, false
• Number 5, 9, 3.1415926
• String Hello World

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Operations and Assignments

• -x reverse the sign of x (negation)
• 65 Add 6 and 5 (numeric)
• Hello World Concatenate two strings
• 2.1 3 Multiply two values
• x increase value of x by 1
• x 5 set the value of x to be 5
• x y x x y
• x 5 x x 5

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Statements

• Simple assignment statements
• celsius 5/9 (f-32)
• Statements that invoke a method
• Temperature.toCelsius(104)
• Return a value from a method
• return celsius

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Methods

• Reusable code for achieving a single task
• function toCelsius(f)
• celsius 5/9 (f-32)
• return celsius

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Basic Control Structures

• Sequential
• Conditional
• Repetition

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Sequential Control Structure
a 2 b 3 c a b
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Conditional Selection Control Structure

• if (gender male)
• greeting Hello, Sir
• else
• greeting Hello, Madam

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Generating Boolean Results

• x y true if x and y are equal
• x ! y true if x and y are not equal
• x gt y true if x is greater than y
• x lt y true if x is smaller than or equal
  to y
• x y true if both x and y are true
• x y true if either x or y is true
• !x true if x is false

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Repetition Control Structure
Program Example 1 n 1 while ( n lt 10)
document.writeln(n) n Program 2 For (n
1 n lt 10 n) document.writeln(n)
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Arrays

• A set of elements
• For example, the number of days in each month
• Each element is assigned an index
• A number used to refer to that element
• For example, x4 is the fifth element (count
  from zero!)
• Arrays and repetitions work naturally together

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Programming for the Web

• Common Gateway Interface (CGI) Server side
• Forms encode field values into a URL
• CGI passes field values to a Perl program
• Program generates a web page as a response
• JavaScript Client-side, interpreted
• Human-readable source code sent to the browser
• Web browser runs the program
• Java applets Client-side, compiled
• Machine-readable bytecode sent to browser
• Web browser runs the program

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JavaScript

• ltHTMLgt
• ltHEADgt
• ltTITLEgtMy first scriptlt/TITLEgt
• lt/HEADgt
• ltBODY BGCOLORWHITEgt
• ltH1gt
• ltSCRIPT LANGUAGEJAVASCRIPT TYPE"TEXT/JAVASCRIPT
  "gt
• document.write("Hello, world!")
• lt/SCRIPTgt
• lt/H1gt
• lt/BODYgtlt/HTMLgt
• Try it at http//www.umiacs.umd.edu/daqingd/Cours
  es/firstscript.html

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Handling Events

• Events
• actions that users perform while visiting the
  page
• Embedded in modern GUI
• Use event handlers to response events
• Event handlers triggered by events
• Examples of event handlers in Javascript
• onMouseover the mouse moved over an object
• onMouseout the mouse moved off an object
• onClick the user clicked on an object

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Hands On Adopt a JavaScript Program

• Launch a Web browser
• http//www.umiacs.umd.edu/daqingd/Courses/selecto
  r.htm
• See how it behaves if you are 13 (or 65)
• View source and read the program
• Save a local copy
• Make some changes and see how it works

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JavaScript Resources

• Google javascript
• Tutorials to learn to write programs
• Code to do things you want to do
• Engineering and Physical Sciences Library
• Books in locked case near circulation desk

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Before You Go!

• On a sheet of paper (no names), answer the
  following question
• What was the muddiest point in todays class?