MIDP: Music and Sound

MIDP: Music and Sound Jussi Pohjolainen TAMK University of Applied Sciences

Sound and Music, the Basics

MIDP 2.0 includes basic audio capabilities

Media API in MIDP 2.0 is a subset of the MMAPI (Mobile Media API).

MMAPI: http://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.

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.

Different content types

Wave audio files:

audio/x-wav

AU audio files:

audio/basic

MP3 audio files:

audio/mpeg

MIDI files:

audio/midi

http://www.iana.org/assignments/media-types/

Audio Data Path Audio Data DataSource Player [ speaker ] For example: applause.wav Handles transporting the data to the player Interface in javax.microedition. media

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

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 (runtime) from Manager which content types and protocols it can handle.

Protocol, for example: http, file, capture .

Manager-class

javac.microedition.media.Manager is the access point for obtaining system dependent resources such as Players for multimedia 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 implementation specific mechanism for constructing Players.

For convenience, Manager also provides a simplified method to generate simple tones .

Supported Protocols and Content types

To find out at runtime what content types and protocols are supported:

Manager -class

public static String[] getSupportedContentTypes(String protocol)

public static String[] getSupportedProtocols(String content_type)

See example: MediaInformationMIDlet.java

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

Player States

Creating 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"

Example of creating Player instance

Example

InputStream in = getClass().getResourceAsStream("/relax.wav");

Player player = Manager.createPlayer(in, "audio/x-wav");

Exception handling is necessary, use try catch.

Example: SimpleGameWithSounds.java

(Maybe the most irritating game of all time)

Controlling Players

Player has following methods that control played sound:

setMediaTime(long now) - jump directly to particular point in an audio clip

setLoopCount(int count) - loop

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);

Optional APIs

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

http://today.java.net/pub/a/today/2005/09/27/j2me4.html

Wireless Messaging API (JSR 205)

Common API for sending and receiving text and binary messages.

http://developers.sun.com/mobility/midp/articles/wma/

Bluetooth API (JSR 82)

Connecting via Bluetooth

Tutorial

http://developers.sun.com/mobility/midp/articles/bluetooth2/

JAXP XML Parser (JSR 172)

This JSR is designed to provide a general purpose XML API for the next generation of mobile devices

Supports

SAX 2 event handler-based parsing

Tutorial

http://developer.sonyericsson.com/site/global/techsupport/tipstrickscode/java/p_xml_parsing_jsr172.jsp

Location API (JSR 179)

Enables developers to write mobile location-based applications for resource-limited devices

Determining device's location (GPS)

Tutorial

http://developers.sun.com/mobility/apis/articles/location/

Mobile Internationalization API (JSR 238)

This JSR defines an API that provides culturally correct data formatting, sorting of text strings and application resource processing for J2ME MIDlets running in MIDP over CLDC.

Tutorial

http://www.ibm.com/developerworks/wireless/library/wi-midapi/

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

http://developers.sun.com/mobility/midp/articles/s2dvg/index.html

That's it...

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