Developing Mobile Applications

1
Developing Mobile Applications

• Mark Green
• School of Creative Media

2
Introduction

• Have looked at some of the tools and techniques
  used to develop mobile applications
• Will now look at more of the details
• Fill in some of the details that we didnt cover
  earlier
• Provide a complete picture of application
  development

3
WARNING

• Some parts of this presentation have a lot of
  technical information
• Will go into some of the technical details
• Dont worry about following everything
• Get the general idea of how things are done, what
  the basic process is
• Know enough to talk about it intelligently

4
Active Content

• Earlier we talked about forms, could collect
  information from user
• Browser sent information to web server
• Web server then generated a response based on the
  users input
• Talked briefly about CGI, the server needs to run
  a program to produce a new web page

5
Active Content

• Look at the details of how this is done
• Want to create web pages that have dynamic
  content
• Respond to user input
• Generate content based on database (search
  engines, eCommerce sites, etc)
• Generate content based on browser (WAP 1, WAP 2,
  standard PC, etc)

6
Active Content

• The old way of doing this was based on writing
  programs
• A C or Java program would retrieve information
  sent by browser
• It would then generate the new page by writing
  all of the html from within the program
• Not easy to do, and hard to change page layout

7
Active Content

• Active content is a way of avoiding most of the
  programming
• A collection of similar techniques, such as ASP
  and JSP
• All based on the same basic idea, just some of
  the details are different
• Allow content designers to design most of the
  page without needing to program

8
Active Content

• Takes the opposite approach to CGI
• Instead of writing a program to generate html,
  put parts of the program into the web page
• Browser doesnt know the difference, it uses the
  same techniques for CGI and active content
• No need to change the browser, all changes are in
  the server

9
Active Content

• The basic idea is very simple
• Most of the web page is done in standard html or
  xhtml
• This is the same as developing a standard web
  page
• The parts of the page that need to be changed are
  handled by a small script that generates the html

10
Active Content

• When a browser asks for an active page the
  following things happen
• The server finds the page
• It copies the standard html directly to the
  browser
• To generate the dynamic parts of the page it runs
  the scripts, sends the output from the scripts to
  the browser
• The server needs to do more work, but the browser
  just sees standard html

11
Active Content

• Basically the same as handling a standard web
  page
• The only difference is the web server runs the
  scripts to generate the dynamic parts of the web
  page
• Active content doesnt use .html or .htm, instead
  is uses .asp or .jsp, so the server knows its an
  active page

12
Active Content

• Most active content systems allow you to select
  the scripting language you want to use
• The most common scripting languages are
  JavaScript and Visual Basic script
• Perl and Python are also quite common, mainly
  used with Apache (the most common web server)

13
Active Content

• Active content is a reasonably good approach to
  developing dynamic web pages
• Web designers can do most of the page design
  using tools the are familiar with
• May need a programmers help to do some of the
  scripting, but once this is done they can keep
  working on the page

14
Active Content

• There are some problems with this approach
• The source for the web pages can be quite long
  and hard to follow, changes may not be that easy
• Scripting language may not be able to do
  everything
• May not be the most efficient approach

15
Summary

• Active content allows us to produce dynamic web
  pages
• Handled completely on the server side, no changes
  to the browser
• Embed scripts in the html for the web page,
  execute by server before sending to browser
• General approach, can be used in standard
  applications as well

16
Summary
Standard Web Page
Find Page
Page Request
Browser
Web Server
HTML Page
HTML Page
HTML Page
Active Content
Run Script
Find Page
Page Request
Browser
Web Server
Active Page
HTML Page
HTML Script
17
Details

• There are many versions of active content
• They all work in basically the same way, only
  differ in some of the details
• Version depends upon the web server that you are
  using
• Most servers only support one type of active
  content, so determine the web server you will be
  using before you start developing active content

18
ASP

• The particular version of active content we will
  look at is ASP (Active Server Pages)
• This is a Microsoft product and is part of their
  IIS web server
• Since we run IIS as our web server, this is the
  natural choice for our examples
• The example discussed here will run on web sites
  hosted at SCM, so you can try it out

19
ASP

• ASP supports a wide range of scripting languages,
  the documentation says over 20
• The main ones are Visual Basic script and
  JavaScript
• We will use Visual Basic script in our examples,
  since its the standard language used with ASP

20
ASP

• The script and the html content are mixed in the
  same file, so how do we separate them?
• Script commands are enclosed in the special tags
  lt and gt
• Anything between these two tags is assumed to be
  script commands by the web server, and it will
  try to run them

21
ASP

• How does the web server know which scripting
  language to use?
• We tell it by including a line like this at the
  beginning of the file
• lt_at_ LanguageVBScript gt
• This line tells the web server that we are using
  Visual Basic script as the scripting language

22
Example One

• To see how this works we will start with a very
  simple example
• We will produce an ASP page that stores a
  greeting in a variable, and then includes this
  greeting in the resulting web page
• We use two lines of script, one to set the
  variable and the other to display the variable

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Example One
lt_at_ LanguageVBScript gt lthtmlgt ltheadgt lttitlegtExam
ple 1lt/titlegt lt/headgt ltbodygt lt Greeting "Hello
world!" gt lt Greetinggt lt/bodygt lt/htmlgt
24
Example One

• There are three lines of interest in this example
• The first line informs the web server of the
  scripting language that we are using
• Later we set the variable Greeting to the string
  we are going to display
• Finally we print the value of Greeting in the web
  page

25
Example One

• To print the value of Greeting we use the
  following
• lt Greetinggt
• a scripting tag that starts with takes the
  value after it and adds it to the web page being
  constructed
• One of the main things we will do is add things
  to web pages, so this short cut is handy

26
Example Two

• Our next example is a bit more sophisticated, we
  will print the greeting 10 times
• We do this with a FOR statement that surrounds
  the line the adds the greeting to the page
• Note in this case we dont have an at the
  beginning, since we dont want the FOR added to
  the web page

27
Example Two
lt_at_ LanguageVBScript gt lthtmlgt ltheadgt lttitlegtExam
ple 2lt/titlegt lt/headgt ltbodygt lt Greeting "Hello
world!" gt ltFOR i 1 TO 10 gt lt
Greetinggt ltNEXTgt lt/bodygt lt/htmlgt
28
Example Two
29
ASP

• This example illustrates the two things that we
  want to do with scripting
• Add something to the web page that is being
  constructed
• Perform some computation that is part of the
  application, or assists with constructing the web
  page
• Not all script commands add to the web page, but
  they can be important parts of the application

30
More Details

• How do we make all of this work with the mobile
  phone simulator?
• In order to retrieve web pages from real web
  sites you need to have the WAP Gateway Simulator
  running
• The simulator redirects your http requests to a
  real web server
• This is similar to what happens with real mobile
  phones

31
Objects

• The web server provides a number of objects that
  we can use in our scripts
• Two of the most important ones are
• Request this object has the information sent
  from the browser when requesting the page, this
  includes the form input
• Response this object contains the information
  that we are sending to the browser

32
Objects

• One of the most important response functions is
  write
• This function adds its parameter to the web page
  that we are building
• It does basically the same thing as lt , but it
  is easier to put in a longer script
• To see how this works we will rewrite the second
  example to use this function

33
Example Three
lt_at_ LanguageVBScript gt lthtmlgt ltheadgt lttitlegtExam
ple 3lt/titlegt lt/headgt ltbodygt lt Greeting "Hello
world!" gt ltFOR i 1 TO 10 response.write
Greeting NEXTgt lt/bodygt lt/htmlgt
34
Form Input

• One of the most important applications of ASP is
  processing form input
• In our previous web examples we produced a number
  of forms, but had no way of processing the
  information collected
• With ASP we can collect that information and use
  it later in our application

35
Example Four
36
Example Four

• This web page allows us to enter a name and
  several other pieces of information
• The name is sent to the browser when we press the
  submit button
• We would like to use this name in subsequent web
  pages, like the following example

37
Example Four
38
Form Input

• The form function in the request object can be
  used to retrieve form input
• The parameter to this function is the name of the
  form item
• Remember each item on a form has a unique name,
  this name is used to retrieve the value of the
  item
• Lets look at the form first

39
Example Four - Form
ltform action"example4.asp" method"post"gt Name
ltinput type"text" name"name" title"Name"
size"10" value"Mark"/gt ltbr/gt ltinput
type"radio" name"status" value"single"
title"single" checked"checked"/gt Single
ltbr/gt ltinput type"radio" name"status"
value"married" title"married" /gt Married
ltbr/gt ltinput type"checkbox" name"now"
title"now" checked"checked"/gt Now
ltbr/gt ltinput type"checkbox" name"today"
title"today"/gt Today ltbr/gt ltinput
type"checkbox" name"tomorrow"
title"tomorrow"/gt Tomorrow ltbr/gt ltinput
type"submit"/gt lt/formgt lt/bodygt
40
Example Four

• This form starts with a text entry box
• The name of this box is name
• When the form is submitted, this property will
  have the name that the user entered
• To retrieve this name from the form we can use
• request.form(name)

41
Example Four - ASP
lt?xml version"1.0" encoding"utf-8"?gt lt!DOCTYPE
html PUBLIC "-//WAPFORUM//DTD XHTML Mobile
1.0//EN" "http//www.wapforum.org/DTD/xhtm
l-mobile10.dtd" gt lthtml xmlns"http//www.w3.org/
1999/xhtml"gt ltheadgt lttitlegtForm
Examplelt/titlegt lt/headgt ltbodygt
lth1gt Response lt/h1gt ltpgt Thank you
for your input lt request.form("name") gt lt
Session("userName") request.form("name") gt
lt/pgt lt/bodygt lt/htmlgt
42
Example Four

• In the ASP page we retrieve the name and add it
  to the web page, this just gives some feedback to
  the user
• But what if we want to use this name on other web
  pages, say later in the session?
• The session object helps us with this
• Each session (a visit to the web site by a single
  user) has its own session object

43
Sessions

• On the first page request a session id and a
  session object are created
• The session id is part of a cookie that is sent
  to the browser
• All the following requests will have this cookie,
  so we know the session the request belongs to
• The session object lasts until the end of the
  session

44
Sessions

• Each session can have its own set of variables
• In this example we are using the variable
  userName to contain the name of the user
• We set the value of this variable in the
  following way
• Session(userName) request.form(name)

45
Sessions

• In any of the subsequent web pages we can add the
  users name to the page in the following way
• lt Session(userName) gt
• A session can have any number of variables and we
  are free to give the variables any name we like
• If we have lots of visitors sessions can take up
  a lot of memory in the server

46
Sessions

• How do we know when a session is over?
• This is hard, browsers dont tell us when they
  are leaving our web site, so we have no way of
  knowing when the user leaves
• ASP handles this by assuming a session has ended
  if there have been no page requests for 20
  minutes
• When the session ends the session object is
  destroyed

47
Saving Data

• Sessions allow us to save data during a session,
  but what about for longer periods of time?
• The application object allows all the users
  running the same application to share data
• This object works the same way as the session
  object, we can create our own variables and
  assign names to them

48
Saving Data

• The application object is destroyed when the web
  server stops running, data stored in it isnt
  permanent
• Also the web administrator must set up the
  application for you, the web server doesnt do it
  automatically
• This might be useful for simple online games or
  chat rooms

49
Saving Data

• Can also use a database to store data
• Can connect to a database from an ASP page, do
  all of the standard database operations
• Retrieve and add data to the database, etc
• This is the best solution if there is a lot of
  data, or a lot of users
• Needs some knowledge of database systems

50
Saving Data

• If the data is relatively simple it can be saved
  in a text file
• Not good for a large amount of data or if
  accessed frequently
• To see how this works we will build a simple
  guest book for our mobile service
• This will use a file to store the names of the
  people who have visited our site

51
Guest Book

• Our guest book is relatively simple, we just
  store names
• Normally some comments on the web site would also
  be saved, but text is hard to enter on mobile
  devices, so we keep it simple
• Would also be hard to display long comments on a
  mobile phone

52
Guest Book

• There are two things that we need
• The first is the form used to collect the names
• And the second is storing the names in the guest
  book file
• This will involve what looks like two pages to
  the user, but will really just be one page on the
  web server

53
Guest Book
54
Guest Book
55
Guest Book

• The guestbook.asp file is divided into two parts
• The first part displays the form and the list of
  names in the guest book
• The second part stores the name from the form
  into the guest book file
• There is a header at the start of the page that
  declares some variables

56
Guest Book
Dim objFSO ' FileSystemObject Variable Dim
objFile ' File Object Variable Dim strFile '
String variable to store the path / file we write
to strFile Server.MapPath("guestbook.txt") Resp
onse.expires -1
57
Guest Book

• The first three lines declare the variables used
  in the script
• The next line gets the complete path to the
  guestbook.txt file
• Server.MapPath adds the directory for the web
  page to the name of the file
• The last line ensures that the page isnt cached
  in the phone, otherwise we cant get back to the
  first part of the page

58
Guest Book

• Next we need to determine if we need to post the
  form
• How can we tell?
• If the request as a non-empty value for the name
  the user must have already entered a name, so we
  dont need to post the form
• A simple if will handle this
• If Request.Form("name") "" Then

59
Guest Book
lth3gtSign Our Guestbooklt/h3gt ltform
action"guestbook.asp" method"post"gt lttablegt lt
trgt ltth align"right"gtNamelt/tdgt lttdgtltinput
type"text" name"name" size"15"gtlt/inputgtlt/tdgt
lt/trgt lt/tablegt ltinput type"submit" value"Sign
Guestbook!"gtlt/inputgt lt/formgt
60
Guest Book

• The form for the guest book is quite straight
  forward
• After displaying the form we need to add the
  names in the guest book
• To do this we open the guestbook.txt file
• Read the file one line at a time and add each
  line to the page we are constructing

61
Guest Book
' Create an instance of the FileSystemObject Set
objFSO Server.CreateObject("Scripting.FileSyste
mObject") ' Open the TextFile (FileName,
ForReading, AllowCreation) Set objFile
objFSO.OpenTextFile(strFile, 1, True) Do While
Not objFile.AtEndOfStream response.write
objFile.ReadLine vbCrLf Loop Set objFile
Nothing Set objFSO Nothing
62
Guest Book

• To read the file we first need to create a file
  system object
• We then use this object to open the text file
  with the names in it
• We then loop through the file, sending it one
  line at a time to the web page
• Finally we set the two object to nothing so they
  will be closed

63
Guest Book

• In the second part the file is opened using
  basically the same technique
• The name is then added to the file, but when we
  do this we add html formatting, so we can just
  copy the line directly to the web page
• We also ensure that the name is properly encoded
  for html

64
Guest Book
' Create an instance of the FileSystemObject Set
objFSO Server.CreateObject("Scripting.FileSyste
mObject") ' Open the TextFile (FileName,
ForAppending, AllowCreation) Set objFile
objFSO.OpenTextFile(strFile, 8,
True) objFile.Write "ltstronggt" objFile.Write
Server.HTMLEncode(Request.Form("name")) objFile.W
rite "lt/stronggtltbr/gt " objFile.WriteLine "" '
Close the file and dispose of our
objects objFile.Close Set objFile
Nothing Set objFSO Nothing
65
Guest Book

• The final thing we need to do is inform the user
  that his or her name has been added
• Also provide a link for going back to the guest
  book

• lth3gtYour comments have been written to the
  file!lt/h3gt
• lta href"guestbook.asp"gtBack to the guestbooklt/agt

66
ASP

• There are a number of other things that can be
  done with ASP
• For example its possible to send mail from an ASP
  page, collect the information for the email from
  a form
• It is also possible to redirect the browser to
  another page, or include content based on the
  type of browser or user input

67
Resources

• There are a number of web sites that have
  information on ASP
• One of the better sites is
• www.asp101.com

68
Ring Tones

• With almost everyone having a mobile phone people
  want some way to customize their phone, make it
  different
• Can change physical appearance by adding covers,
  etc
• One of the most popular customization is ring
  tones, something that be heard and is obvious

69
Ring Tones

• Now big business, one of the most profitable
  mobile data services
• Becoming a multi B industry, to the outsider
  really doesnt look like it, but
• Many people have phones, many can add ring tones
  easy to do and understand
• Each ring tone costs around 15
• Carrier makes 1 - 3 off of each ring tone
  download

70
Ring Tones
71
Ring Tones
72
Ring Tones

• Music industry looking at ring tones as
  replacement for singles and radio
• Old model
• A few singles produced from each album
• Singles played on radio, often before album
  released
• Requests and sales generate hit status
• Used to generate sales for the album

73
Ring Tones

• Radio industry in trouble, with Internet hard to
  measure, sales of singles has disappeared, no 45
  rpm records
• But, can easily measure number of ring tone
  downloads
• With increasing audio quality, ring tones could
  sound as good as radio
• Record industry seriously considering them

74
Ring Tones

• Important considerations
• Song are relatively short, 2 or 3 minutes
• Ideal mobile content, easy to consume on the road
• Popular for a short period of time, phone has
  limited storage, can be discarded when next hit
  comes along
• Download both song and ring tone based on song,
  what a package!

75
Technology

• Several technologies for ring tones have been
  developed over the years
• Get more complex as phones gain more capabilities
• Early ring tones were monophonic (one note at a
  time)
• Sent to the phone over SMS, so they couldnt be
  very long

76
Monophonic

• Encoding of the ring tone is quite simple, in
  some ways it resembles a very simple version of
  Midi
• A small set of instructions, the common ones are
• Tempo
• Note
• Scale
• Pause

77
Monophonic

• Notes are specified as their position within the
  octave, number between 0 and 12
• Durations specified in terms of standard musical
  notation, not in terms of seconds
• Scale command used to change the octave used
• Pause is used to produce a rest
• Can define repeating patterns

78
Technology

• Most phones now have polyphonic (more than one
  note at a time) ring tones
• Still need to worry about amount of memory
  required to store ring tones, so cant do sampled
  sounds
• Need a more compact format
• This opens up a lot of possibilities, can have
  much more sophisticated sounds

79
Technology

• Midi is one of the standards used for polyphonic
  ring tones
• Reasonably compact representation, only a few
  bytes per note
• Well known format
• Many composers are familiar with it, can easily
  produce content
• Many composition tools are already available,
  dont need to create new ones

80
Technology

• Problem different phones have different
  capabilities
• Size of ring tones, this is obvious and easy to
  control
• Level of polyphony, number of notes that can be
  played at the same time, this is the real problem
• PC Midi synthesizers can play at least 64 notes
  at the same time, not the case with phones

81
Technology

• First polyphonic phones could only play 4 notes
  at a time
• Second generation phones could play 16 notes at a
  time
• Some current phones can play 24 or more notes at
  the same time
• Nice to see the evolution of capabilities, but
  this causes a problem

82
Technology

• If we want to support the widest range of phones,
  restrict to 4 note polyphony
• But, this wastes the capabilities of other
  phones, we could produce much better ring tones
  for these phones
• If we aim for more polyphony it could sound bad
  on low end phones
• Wont be able to play all the notes

83
SP-Midi

• Would like our ring tones to sound good on all
  phones
• Dont want to produce separate versions for each
  type of phone
• May not be possible to determine phone
  capabilities before download
• Scalable Polyphonic Midi is one solution to this
  problem

84
SP-Midi

• If I compose a ring tone assuming 16 level
  polyphony and someone plays it on a phone with 4
  level polyphony there will be problems
• Phone can only play 4 notes at a time, but the
  ring tone could need 16
• If we are already playing 4 notes and the ring
  tone asks for a fifth note what will happen?

85
SP-Midi

• Could do one of two things
• Could select one of the current notes, stop
  playing it and start playing the new note
• Ignore the new note and keep playing the current
  4 notes
• Both of these solutions could cause problems,
  depending upon the role of the new note
• Need to know how important it is

86
SP-Midi

• If the new note is part of the melody, want to
  stop one of the current notes and play the new
  one
• If the new note isnt as important as the current
  notes, then want to keep playing them
• Dont want to stop an important melody note for
  one that isnt as important

87
SP-Midi

• The phone doesnt know which notes are important,
  it has no musical knowledge
• Phone is likely to play the wrong notes, ring
  tone will sound bad
• SP-Midi provides a solution to this problem
• It gives the composer several ways of indicating
  the notes that should be played on less capable
  phones

88
SP-Midi

• Priority scheme is based on channels
• Recall a Midi channel is like an instrument, all
  the notes on the same channel played by the same
  instrument
• Can have several simultaneous notes on the same
  channel
• First, each channel is assigned a priority by the
  composer

89
SP-Midi

• Composer puts the most important notes in the
  channel with the highest priority
• For example, the melody would be placed in the
  highest priority channel
• The least important parts of the song would be
  placed in the channels with the lowest priorities
• Composer must carefully design the song so the
  most important parts are played

90
SP-Midi

• This solves part of the problem
• The phone will always play the most important
  notes, but it could still sound bad
• If a low priority note is playing and a more
  important one comes along, the lower priority
  note will immediately stop playing
• This can be quite noticeable, it would be better
  if the lower priority note didnt start

91
SP-Midi

• We need some way of saying dont play these
  channels, even if at some point there are
  resources for them
• The MIP (Maximum Instantaneous Polyphony) Midi
  message is used to solve this problem
• Matches the channels to the polyphony level of
  the phone

92
SP-Midi

• For each polyphony level the MIP message gives
  the set of channels that can be played
• A 4 note phone can then pick the set of channels
  that will play at most 4 notes at the same time
• The phone will ignore all of the other channels,
  so the ring tone will sound reasonable on any
  phone

93
SP-Midi

• SP-Midi ring tones can either be delivered by MMS
  or WAP
• With MMS the phone sends an SMS message to the
  server requesting a particular ring tone
• The server responds with an MMS message
  containing the ring tone
• The phone adds the ring tone to its list

94
SP-Midi

• In the case of WAP delivery, the user browses to
  the web page with the ring tones
• Selecting a link will download a ring tone using
  a standard WAP response
• Similar to a normal web page download
• Ring tone can then be played and added to the
  list of ring tones for the phone

95
Technology

• Now that phones have more memory its possible to
  use sampled ring tones
• This is quite recent and only a small number of
  phones support it
• True Tone ring tones are based on the AMR-WB
  audio format
• This format was originally designed for speech,
  but can be used for music

96
True Tone

• AMR-WB requires 1-3 kBytes per second of sound
• Most 2.5G services restricted downloads to
  between 30 and 100 kBytes
• The maximum is about a minute of good quality
  sound, but could be as little as 10 seconds
• This is not a problem with 3G phones

97
True Tone

• Why use True Tone ring tones
• Can have a much wider range of sounds
• Can use existing sounds/music that is already is
  a sampled format
• Easy to produce by converting existing sound
  files
• Can do novelty ring tones, like people talking or
  sound effects

98
True Tone

• Can be downloaded using either MMS or WAP, the
  same as SP-Midi ring tones
• Fairly new, and not a very large market yet so
  they are not very popular
• Relatively slow download on 2.5G, better on 3G,
  but they might define a different set of
  standards for ring tones

99
Composing Ring Tones

• Its a mobile phone, not a high end home stereo
  system!
• Phones have a small speaker, not very good audio
  quality
• Only have good quality when headphones are used
• Stay in the narrow frequency range used for voice
  communications

100
Composing Ring Tones

• Avoid high and low frequencies
• Use instruments that have a solid sound, not a
  weak one
• Phones often used in noisy environments, the ring
  must be heard!
• Need to have enough volume in the ring tone, no
  quiet sweet melodies
• Be a bit (a lot??) annoying

101
Composing Ring Tones

• Remember that a ring tone repeats
• The phone doesnt ring just once, it can ring
  several times
• The end of the ring tone must flow into its start
• Better to use a short riff than a longer
  sequence, it will repeat better

102
Composing Ring Tones

• There are several tricks that can be done with
  SP-Midi ring tones
• Volume can be increased by repeating a channel,
  particularly if the channel is played by a weak
  instrument
• This is easy to do in a sequencer, just duplicate
  the track
• Repeating more than once probably wont help much

103
Composing Ring Tones

• Duplicating tracks can be used for several other
  effects
• Using a small time delay will produce an echo
  like effect
• This will give the ring tone more depth and
  partially compensate for small speakers
• Slightly detuning the second track gives an
  interesting, if not annoying effect

104
Composing Ring Tones

• Remember to try the ring tones on real phones
• What sounds good on your computer may not sound
  good on a phone, computers have better speakers
  and sound cards
• Some ring tone composing software can simulate
  phone speakers, giving the composer some idea of
  what it will sound like on a phone

105
DRM

• Digital Rights Management protecting your
  content from pirates
• If you can download content for your phone,
  whats to stop people from pirating it, making
  illegal copies
• Set up their own web site for ring tones based on
  copied content
• Major concern in the content industry

106
DRM

• The content industry was too late for the
  Internet, pirating well established before they
  knew about the Internet
• Dont want to be left behind with mobile media
• Content industry now playing an active role in
  media distribution technology before it is
  released

107
DRM

• Piracy is probably not as large a threat for
  mobile media
• The technology makes piracy more difficult and
  less profitable
• Download cost is relatively low, so there isnt
  much of a profit margin for pirates, their costs
  will be similar to the developers
• More risky, easier to get caught

108
Mobile vs. Internet

• Small number of carriers
• Pirates in competition with carriers
• Pirates have negative impact on revenue
• Pirates are relatively easy to block

• Large number of carriers
• No competition between pirates and carriers
• Pirates have a positive impact on revenue
• Pirates are very hard to block

109
DRM

• Unlike the internet, pirates are in competition
  with carriers
• Carriers get a portion of the revenue from
  content, if content is pirated carrier loses this
  revenue
• With very few carriers its quite easy to block a
  pirate, dont allow requests to their web site

110
DRM

• Distribution over the air not possible for
  pirates
• This leaves burning CDs and downloading from
  customers computer
• Since most content downloads are around 15,
  pirates will need to charge around 5 or 6 to
  get sales, customers wont pay 25 for the
  pirated version
• No profit margin

111
DRM

• Unlike PCs, mobile phones are hard to hack, but
  not impossible
• Only a few manufacturers, cannot be custom built
• Cannot install your own operating software, done
  by manufacturer
• Much tighter control over what can be done on the
  phone

112
DRM

• The OMA (Open Mobile Alliance) has defined three
  methods of DRM, only the first method is widely
  used
• Forward-lock prevents content from being
  forwarded to another phone
• A user can download the content and play the
  content
• The content can be sent to another phone, but
  that phone cannot view the content

113
DRM

• On download the content is encrypted with a key
  that is unique to the phone
• Only the phone that it was downloaded to has the
  key, so it can only be viewed on that phone
• The content is only stored in the encrypted form,
  it is never in plain form
• This works for all types of content, both
  streaming and download

114
DRM

• There is one hole in this approach, for Java
  applications the installation package isnt
  encrypted
• The encryption happens after the application is
  installed
• A user can forward the installation package to
  another phone, and the application could be
  potentially installed there

115
DRM

• There are several ways around this, including
  getting a key before the package can be installed
• Combined Delivery both the content and the
  rules and keys for accessing the content are
  downloaded together
• Different rules can be applied to different parts
  of the content

116
DRM

• User could be able to preview the content without
  paying, but would need to obtain a key to view
  the entire content
• More flexible than forward-lock, can give
  different levels of access to different parts of
  the content
• Forward-lock is all or nothing, cant give
  selective access

117
DRM

• Separate Delivery separates the content from the
  keys and access rights, they are downloaded as
  two separate packages
• The most secure and flexible of the three methods
• User must have both parts to access the content,
  the content part can be freely distributed, but
  cannot be accessed without the second part

118
DRM

• Since the access rights are separate they can be
  time dependent, for example view once, or view
  for a week
• The content developer can rely on multiple
  channels to distribute the content, even pirates
• They control distribution of the access rights, a
  much smaller download

119
DRM

• This is not a consumer friendly as the other
  approaches
• Forward-lock is available now on newer phones,
  but the other two have not been widely deployed
  yet
• Free tools available for adding forward-lock to
  content, can be done now with very little work

120
MMS

• So far treated SMS and MMS as basically the same,
  but this really isnt the case
• There are two main differences
• Message transfer mechanism
• Message content
• We are mainly interested in message content, but
  will briefly look at transfer as well

121
Message Transfer

• Unlike an SMS a MMS message is not delivered
  immediately to a phone
• Instead the phone is sent a message notification,
  telling the phone that a message is waiting
• The message notification contains a URL that
  tells the phone how to retrieve the message

122
Message Transfer

• If the user wants the message, they can tell the
  phone to retrieve it
• The user can also ignore the message, this can
  save money since the messages could be large
• Message retrieval is usually over http, but other
  protocols could be used

123
Message Transfer

• Similarly when you send an MMS, the whole message
  goes to the MMSC, but only the notification goes
  to the person you sent it to
• They can then decide to download your MMS or
  ignore it
• A receive notification may not mean that the
  person has viewed the message, only the
  notification

124
Message Content

• An MMS message can have a single media item, a
  picture from the phones camera
• This is typically the case when you send an MMS
  from your phone
• In other cases it can have multiple items, in
  this case there needs to be presentation
  information as well

125
Message Content

• A message produced by a service will have
  multiple items, for example text, image and
  sound, in the same message
• If there are multiple images, or videos, where do
  we put them on the screen?
• What is the timing of the individual components?
• This is handled by the presentation part of the
  message

126
Presentation

• An MMS message consists of multiple parts
• The presentation component
• The individual media items
• SMIL, Synchronized Multimedia Integration
  Language is used for the presentation component
• A standard multimedia language, not restricted to
  phones

127
SMIL

• SMIL description divided into two parts
• Head the screen layout and transitions, the
  spatial part of the presentation
• Body the timing and duration of the individual
  media pieces, the temporal part of the
  presentation
• The head divides the screen into a number of
  regions, regions can overlap, define a stacking
  order

128
SMIL

• Region size and position can be specified in
  pixels, or percentage of the screen size
• Can specify both the size and position of a
  region
• Transitions can be used at the beginning or end
  of a media item
• Transitions usually applied to text and images,
  dont work with video

129
SMIL

• The body specifies the items to be displayed,
  give name of media and region where its displayed
• Also give timing information, can have a duration
  for each item, and a start time
• Can also have in and out transitions for each item

130
SMIL

• With multiple items can be displayed in parallel
  of sequentially
• Grouping items are used for this
• In a ltpargt group all the items are displayed in
  parallel
• In a ltseqgt group they are displayed one after the
  other
• Can put a ltpargt in a ltseqgt and visa versa

131
SMIL

• SMIL is an XML based language, so it looks like
  HTML
• In the lab we will look at the software that can
  be used to create MMS messages and look at some
  examples