The document discusses the basics of sound and music capabilities in MIDP 2.0, including the Media API subset called the Audio Building Block. It describes playing audio files of different content types like WAV, MP3, and MIDI. The relationship between classes like Manager, DataSource and Player for controlling audio playback is also covered at a high level.

1. MIDP:
Music
and
Sound
Jussi
Pohjolainen
Tampere
University
of
Applied
Sciences

2. Sound
and
Music,
the
Basics
• MIDP
2.0
includes
basic
audio
capabiliEes
• Media
API
in
MIDP
2.0
is
a
subset
of
the
MMAPI
(Mobile
Media
API).
– MMAPI:
hHp://jcp.org/en/jsr/detail?id=135
• Subset
of
the
MMAPI
that
is
included
in
MIDP
2.0
is
called
Audio
Building
Block
(ABB).
– Features:
Playing
simple
tones
and
sampled
audio
• Media
API
can
also
be
used
as
playing
all
kinds
of
media,
for
example
movies.

3. MIDP
2.0
Media
Concepts
• Audio
data
comes
in
variety
of
content
types.
• Content
type
=
file
format!
– MP3,
AIFF,
WAF
etc.
• Content
types
are
specified
using
MIME
types,
which
use
a
string
to
specify
a
1)
primary
and
2)
secondary
type.
– Example:
"audio/x-­‐wav"
• Content
type
tells
how
to
translate
bits
into
sound.

4. Different
content
types
• Wave
audio
files:
– audio/x-­‐wav
• AU
audio
files:
– audio/basic
• MP3
audio
files:
– audio/mpeg
• MIDI
files:
– audio/midi
• hHp://www.iana.org/assignments/media-­‐
types/

5. Audio
Data
Path
For
example:
Handles
Interface
in
applause.wa transporEng
the
javax.microediEon.
data
to
the
v
media
player
Audio
DataSource
Player
Data
[
speaker
]

6. RelaEonship
between
classes
Manager
creates
a
player
with
certain
content
types
and
protocols
Manager
creates
DataSource
Player
Controllers
can
control
tone
and
volume
Control

7. Supported
Content
Types
and
Protocols
• MIDP
2.0
spec:
if
sampled
audio
is
supported
at
all,
then
8-­‐bit
PCM
WAV
must
be
supported.
– WAV
is
guaranteed..
your
mobile
phone
can
support
other
content
types,
for
example
mp3.
• It
is
possible
to
ask
(runEme)
from
Manager
which
content
types
and
protocols
it
can
handle.
• Protocol,
for
example:
hCp,
file,
capture.

8. Manager-­‐class
• javac.microedition.media.Manager
is
the
access
point
for
obtaining
system
dependent
resources
such
as
Players
for
mulEmedia
processing.
• A
Player
is
an
object
used
to
control
and
render
media
that
is
specific
to
the
content
type
of
the
data.
• Manager
provides
access
to
an
implementaEon
specific
mechanism
for
construcEng
Players.
• For
convenience,
Manager
also
provides
a
simplified
method
to
generate
simple
tones.

9. Supported
Protocols
and
Content
types
• To
find
out
at
runEme
what
content
types
and
protocols
are
supported:
– Manager-­‐class
• public static String[]
getSupportedContentTypes(String protocol)!
• public static String[]
getSupportedProtocols(String content_type)!
• See
example:
MediaInformaEonMIDlet.java

10. Player
Life
Cycle
• Player
has
detailed
life
cycle
• Life
cycle
has
states:
– UNREALIZED
• Player
is
created,
but
it
hasn't
tried
to
find
audio
data.
– REALIZED
• Media
data
is
located.
– PREFETCHED
• Audio
data
is
fetched
and
ready
to
go
– STARTED
• Audio
data
is
playing
– CLOSED
• All
resources
are
released

11. Player
States

12. CreaEng
a
Player
• Player
is
created
using
by
Manager
class
• public static Player createPlayer(InputStream stream,
String type)!
• Example
• Player player = Manager.createPlayer(...);!
• Parameters
– Stream
to
the
data
file.
– String
type
=
content
type,
example:
"audio/x-­‐
wav"

13. Example
of
creaEng
Player
instance
• Example
• InputStream in = getClass().getResourceAsStream("/
relax.wav");!
• Player player = Manager.createPlayer(in, "audio/x-wav");!
• ExcepEon
handling
is
necessary,
use
try
catch.
• Example:
SimpleGameWithSounds.java
– (Maybe
the
most
irritaEng
game
of
all
Eme)

14. Controlling
Players
• Player
has
following
methods
that
control
played
sound:
– setMediaTime(long now)
-­‐
jump
directly
to
parEcular
point
in
an
audio
clip
– setLoopCount(int count)
-­‐
loop

15. Player
Controls
• Control
classes
can
control
Players
• You
can
obtain
a
list
of
Controls
for
a
Player
by
calling
getControls().
• MIDP
2.0
has
only
two
Controls
for
the
Player:
– VolumeControl
– ToneControl!
• Example
of
usage:
– VolumeControl vc = (VolumeControl)
player.getControl("VolumeControl");!
– vc.setLevel(50);

16. OpEonal
APIs

17. Mobile
Media
API
(JSR
135)
• Playing
sounds
and
tones
• Also
capturing
media
– MMAPI
supports
capturing
audio
and
video
from
onboard
hardware
– Recording
sound,
video
and
taking
pictures
• hHp://today.java.net/pub/a/today/
2005/09/27/j2me4.html

18. Wireless
Messaging
API
(JSR
205)
• Common
API
for
sending
and
receiving
text
and
binary
messages.
• hHp://developers.sun.com/mobility/midp/
arEcles/wma/

19. Bluetooth
API
(JSR
82)
• ConnecEng
via
Bluetooth
• Tutorial
– hHp://developers.sun.com/mobility/midp/
arEcles/bluetooth2/

20. JAXP
XML
Parser
(JSR
172)
• This
JSR
is
designed
to
provide
a
general
purpose
XML
API
for
the
next
generaEon
of
mobile
devices
• Supports
– SAX
2
event
handler-­‐based
parsing

21. LocaEon
API
(JSR
179)
• Enables
developers
to
write
mobile
locaEon-­‐
based
applicaEons
for
resource-­‐limited
devices
• Determining
device's
locaEon
(GPS)
• Tutorial
– hHp://developers.sun.com/mobility/apis/
arEcles/locaEon/

22. Mobile
InternaEonalizaEon
API
(JSR
238)
• This
JSR
defines
an
API
that
provides
culturally
correct
data
formakng,
sorEng
of
text
strings
and
applicaEon
resource
processing
for
J2ME
MIDlets
running
in
MIDP
over
CLDC.
• Tutorial
– hHp://www.ibm.com/developerworks/wireless/
library/wi-­‐midapi/

23. Scalable
2D
Vector
Graphics
API
for
J2ME
(JSR
226)
• Scalable
2D
Vector
Graphics
API
for
J2ME
(JSR
226)
provides
MIDlets
with
an
API
for
displaying
SVG
content.
• Tutorial
– hHp://developers.sun.com/mobility/midp/
arEcles/s2dvg/index.html