javax.microedition.media
Class Manager

java.lang.Object
  |
  +--javax.microedition.media.Manager

public final class Manager

extends java.lang.Object

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.

Simple Tone Generation

The playTone function is defined to generate tones. Given the note and duration, the function will produce the specified tone.

Creating Players

Manager provides three methods to create a Player for playing back media:

• Create from a media locator.
• Create from a DataSource.
• Create from an InputStream.

The Player returned can be used to control the presentation of the media.

The simplest way to create a Player is from a locator in the URI syntax. Given a locator, createPlayer will create a Player suitable to handle the media identified by the locator.

Users can also implement a custom DataSource to handle an application-defined protocol. The custom DataSource can be used to create a Player by using the createPlayer method.

A third version of createPlayer creates a Player from an InputStream. This can be used to interface with other Java API's which use InputStreams such as the java.io package. It should be noted that InputStream does not provide the necessary random seeking functionality. So a Player created from an InputStream may not support random seeking (ala Player.setMediaTime).

System Time Base

All Players need a TimeBase. Many use a system-wide TimeBase, often based on a time-of-day clock. Manager provides access to the system TimeBase through getSystemTimeBase.

Content Types

Content types identify the type of media data. They are defined to be the registered MIME types ( http://www.iana.org/assignments/media-types/); plus some user-defined types that generally follow the MIME syntax (RFC 2045, RFC 2046).

For example, here are a few common content types:

1. Wave audio files: audio/x-wav
2. AU audio files: audio/basic
3. MP3 audio files: audio/mpeg
4. MIDI files: audio/midi
5. Tone sequences: audio/x-tone-seq
6. MPEG video files: video/mpeg

Data Delivery Protocol

A data delivery protocol specifies how media data is delivered to the media processing systems. Some common protocols are: local file, disk I/O, HTTP, RTP streaming, live media capture etc.

Media locators are used to identify the delivery protocol (as well as the identifier/name of the media).

Media Locator

Media locators are specified in URI syntax which is defined in the form:

<scheme>:<scheme-specific-part>

The "scheme" part of the locator string identifies the name of the protocol being used to deliver the data.

Some media specific locator syntax are defined below:

1. Locators for Live-media Capture

The locators for capturing live media are defined by the following syntax in Augmented BNF notations:

     "capture://" device [ "?" params]
 

A. Identifying the type or the specific name of the device:

     device       = "audio" / "video" / "audio_video" / dev_name
     dev_name     = alphanumeric
     alphanumeric = 1*( ALPHA / DIGIT )
 

B. Describing the media and capture parameters:

     params = audio_params / video_params / 
              audio_video_params / custom_params
 

C. Describing the audio media format:

     audio_params = audio_param *( "&" audio_param )
     audio_param  = 1*( "encoding=" audio_enc / "rate=" rate / 
                        "bits=" bits / "channels=" channels / 
                        "endian=" endian / "signed=" signed )
     audio_enc    = "pcm" / "ulaw" / "gsm"
     rate         = "96000" / "48000" / "44100" / "22050" / "16000" / 
                    "11025" / "8000"
     bits         = "8" / "16" / "24"
     channels     = pos_integer
     endian       = "little" / "big"
     signed       = "signed" / "unsigned"
     pos_integer  = 1*DIGIT
   

   Example:
   

     encoding=pcm&rate=11025&bits=16&channels=1
 

D. Describing the video or image format:

     video_params = video_param *( "&" video_param )
     video_param  = 1*( "encoding=" video_enc / "width=" width / 
                       "height=" height / "fps=" fps )
     video_enc    = "gray8" / "rgb888" / "bgr888" / "rgb565" / "rgb555" / 
                    "yuv444" / "yuv422" / "yuv420" / "jpeg" / "png"
     width        = pos_integer
     height       = pos_integer
     fps          = pos_number
     pos_number   = 1*DIGIT [ "." 1*DIGIT ]
   

   Example:
   

     encoding=gray8&width=160&height=120
 

E. Describing audio and video parameters:

     audio_video_params = audio_params "&" video_params
   

   Example:
   

     encoding=pcm&encoding=gray8&width=160&height=160
 

F. Describing some custom media parameters:

     custom_params = param *( "&" param ) 
     param         = key "=" value
     key           = alphanumeric
     value         = alphanumeric
   

   Examples:
   

     capture://audio  (default audio)
     capture://audio?encoding=pcm   (default audio in PCM format)
     capture://devmic0?encoding=pcm&rate=11025&bits=16&channels=1  
             (audio from a specific device--devmic0)
     

     capture://video  (default video)
     capture://video?encoding=gray8&width=160&height=120
     capture://devcam0?encoding=rgb888&width=160&height=120&fps=7
     

     capture://mydev?myattr=123   (custom device with custom param)
 

2. Locators for RTP streaming

RTP is a public standard for streaming media. The locator syntax for specifying RTP sessions is:

     "rtp://" address [ ":" port ] [ "/" type ]
   

   where:
   

     address and port defines the RTP session.  The
     address and port usage is similar to the host and port
     usage as defined in the URI syntax.
     

     type = "audio" / "video" / "text"
 

See Also:

DataSource, Player, TimeBase

Field Summary

static java.lang.String	MIDI_DEVICE_LOCATOR The locator to create a MIDI Player which gives access to the MIDI device by making MIDIControl available.
static java.lang.String	TONE_DEVICE_LOCATOR The locator to create a tone Player to play back tone sequences.

Method Summary

static Player	createPlayer(DataSource source) Create a Player for a DataSource.
static Player	createPlayer(java.io.InputStream stream, java.lang.String type) Create a Player to play back media from an InputStream.
static Player	createPlayer(java.lang.String locator) Create a Player from an input locator.
static java.lang.String[]	getSupportedContentTypes(java.lang.String protocol) Return the list of supported content types for the given protocol.
static java.lang.String[]	getSupportedProtocols(java.lang.String content_type) Return the list of supported protocols given the content type.
static TimeBase	getSystemTimeBase() Get the time-base object for the system.
static void	playTone(int note, int duration, int volume) Play back a tone as specified by a note and its duration.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

TONE_DEVICE_LOCATOR

public static final java.lang.String TONE_DEVICE_LOCATOR

The locator to create a tone Player to play back tone sequences. e.g.

 try {
     Player p = Manager.createPlayer(Manager.TONE_DEVICE_LOCATOR);
     p.realize();
     ToneControl tc = (ToneControl)p.getControl("ToneControl");
     tc.setSequence(mySequence);
     p.start();
 } catch (IOException ioe) {
 } catch (MediaException me) {}
 

If a tone sequence is not set on the tone Player via its ToneControl, the Player does not carry any sequence. getDuration returns 0 for this Player.

The content type of the Player created from this locator is audio/x-tone-seq.

A Player for this locator may not be supported for all implementations.

Value "device://tone" is assigned to TONE_DEVICE_LOCATOR.

MIDI_DEVICE_LOCATOR

public static final java.lang.String MIDI_DEVICE_LOCATOR

The locator to create a MIDI Player which gives access to the MIDI device by making MIDIControl available. e.g.

 try {
     Player p = Manager.createPlayer(Manager.MIDI_DEVICE_LOCATOR);
     p.prefetch(); // opens the MIDI device
     MIDIControl m = (MIDIControl)p.getControl("MIDIControl");
 } catch (IOException ioe) {
 } catch (MediaException me) {}
 

The MIDI Player returned does not carry any media data. getDuration returns 0 for this Player.

The content type of the Player created from this locator is audio/midi.

A Player for this locator may not be supported for all implementations.

Value "device://midi" is assigned to MIDI_DEVICE_LOCATOR.

Method Detail

getSupportedContentTypes

public static java.lang.String[] getSupportedContentTypes(java.lang.String protocol)

Return the list of supported content types for the given protocol.

See content types for the syntax of the content types returned. See protocol name for the syntax of the protocol used.

For example, if the given protocol is "http", then the supported content types that can be played back with the http protocol will be returned.

If null is passed in as the protocol, all the supported content types for this implementation will be returned. The returned array must be non-empty.

If the given protocol is an invalid or unsupported protocol, then an empty array will be returned.

Parameters:

protocol - The input protocol for the supported content types.

Returns:

The list of supported content types for the given protocol.

getSupportedProtocols

public static java.lang.String[] getSupportedProtocols(java.lang.String content_type)

Return the list of supported protocols given the content type. The protocols are returned as strings which identify what locators can be used for creating Player's.

See protocol name for the syntax of the protocols returned. See content types for the syntax of the content type used.

For example, if the given content_type is "audio/x-wav", then the supported protocols that can be used to play back audio/x-wav will be returned.

If null is passed in as the content_type, all the supported protocols for this implementation will be returned. The returned array must be non-empty.

If the given content_type is an invalid or unsupported content type, then an empty array will be returned.

Parameters:

content_type - The content type for the supported protocols.

Returns:

The list of supported protocols for the given content type.

createPlayer

public static Player createPlayer(java.lang.String locator)
                           throws java.io.IOException,
                                  MediaException

Create a Player from an input locator.

Parameters:

locator - A locator string in URI syntax that describes the media content.

Returns:

A new Player.

Throws:

IllegalArgumentException - Thrown if locator is null.

MediaException - Thrown if a Player cannot be created for the given locator.

java.io.IOException - Thrown if there was a problem connecting with the source pointed to by the locator.

SecurityException - Thrown if the caller does not have security permission to create the Player.

createPlayer

public static Player createPlayer(DataSource source)
                           throws java.io.IOException,
                                  MediaException

Create a Player for a DataSource.

Parameters:

source - The DataSource that provides the media content.

Returns:

A new Player.

Throws:

IllegalArgumentException - Thrown if source is null.

MediaException - Thrown if a Player cannot be created for the given DataSource.

java.io.IOException - Thrown if there was a problem connecting with the source.

SecurityException - Thrown if the caller does not have security permission to create the Player.

createPlayer

public static Player createPlayer(java.io.InputStream stream,
                                  java.lang.String type)
                           throws java.io.IOException,
                                  MediaException

Create a Player to play back media from an InputStream.

The type argument specifies the content-type of the input media. If null is given, Manager will attempt to determine the type. However, since determining the media type is non-trivial for some media types, it may not be feasible in some cases. The Manager may throw a MediaException to indicate that.

Parameters:

stream - The InputStream that delivers the input media.

type - The ContentType of the media.

Returns:

A new Player.

Throws:

IllegalArgumentException - Thrown if stream is null.

MediaException - Thrown if a Player cannot be created for the given stream and type.

java.io.IOException - Thrown if there was a problem reading data from the InputStream.

SecurityException - Thrown if the caller does not have security permission to create the Player.

playTone

public static void playTone(int note,
                            int duration,
                            int volume)
                     throws MediaException

Play back a tone as specified by a note and its duration. A note is given in the range of 0 to 127 inclusive. The frequency of the note can be calculated from the following formula:

     SEMITONE_CONST = 17.31234049066755 = 1/(ln(2^(1/12)))
     note = ln(freq/8.176)*SEMITONE_CONST
     The musical note A = MIDI note 69 (0x45) = 440 Hz.
 

This call is a non-blocking call. Notice that this method may utilize CPU resources significantly on devices that don't have hardware support for tone generation.

Parameters:

note - Defines the tone of the note as specified by the above formula.

duration - The duration of the tone in milli-seconds. Duration must be positive.

volume - Audio volume range from 0 to 100. 100 represents the maximum volume at the current hardware level. Setting the volume to a value less than 0 will set the volume to 0. Setting the volume to greater than 100 will set the volume to 100.

Throws:

IllegalArgumentException - Thrown if the given note or duration is out of range.

MediaException - Thrown if the tone cannot be played due to a device-related problem.

getSystemTimeBase

public static TimeBase getSystemTimeBase()

Get the time-base object for the system.

Returns:

The system time base.