javax.microedition.media

Class Manager

java.lang.Object

javax.microedition.media.Manager

public final class Manager
extends 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 [ "?" media_encodings ]
 

To identify the type or the specific name of the device:

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

The syntax for specifying the media encodings are defined in Media Encoding Strings.

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"
 

Example:

     rtp://224.1.2.3:12344/audio
 

3. Locators for Radio Tuner

To create a Player to tune into a radio program, the following locator syntax is used:

     "capture://radio" [ "?" tuner_params ]
 

where:

     tuner_params = tuner_param *( "&" tuner_param )
     tuner_param  = "f=" freq /
                    "mod=" modulation /
                    "st=" stereo_mode /
                    "id=" program_id /
                    "preset=" preset
     freq         = megahertz /
                    kilohertz /
                    hertz
     megahertz    = pos_integer "M" /
                    pos_integer "." pos_integer "M"
     kilohertz    = pos_integer "k" /
                    pos_integer "." pos_integer "k"
     hertz        = pos_integer
     modulation   = "fm" / "am"
     stereo_mode  = "mono" / "stereo" / "auto"
     program_id   = alpanumeric ; identifies an FM channel by its
                                  program service name (PS) delivered
                                  via Radio Data System (RDS)**.
     preset       = pos_integer ; predefined tuning number
 

** The RDS specification is available from http://bsonline.techindex.co.uk, id BSEN 50067:1998.

Examples:

     capture://radio?f=91.9M&st=auto
               (91.9 MHz with automatic stereo setting)
     capture://radio?f=558k&mod=am
               (558 kHz with amplitude modulation)
     capture://radio?id=yleq
               (FM channel that has "yleq" as its program service name
                delivered via Radia Data System)
 

Media Encoding Strings

There are a few places where media encodings are specified as strings, e.g. in the capture media locator. Sections A to E define the encoding syntax. Section F defines the rules for how they should be handled.

A. Describing media encodings:

     media_encodings = audio_encodings /
                       video_encodings /
                       mixed_encodings /
                       custom_encodings
 

B. Describing the audio encodings:

     audio_encodings = audio_enc_param *( "&" audio_param )
     audio_enc_param = "encoding=" audio_enc
     audio_enc       = "pcm" / "ulaw" / "gsm" / content_type
     audio_param     = "rate=" rate /
                       "bits=" bits /
                       "channels=" channels /
                       "endian=" endian /
                       "signed=" signed /
                       "type=" audio_type
     rate            = "96000" / "48000" / "44100" /
                       "22050" / "16000" / "11025" /
                       "8000" / other_rate
     other_rate      = pos_integer
     bits            = "8" / "16" / "24" / other_bits
     other_bits      = pos_integer
     channels        = pos_integer
     endian          = "little" / "big"
     signed          = "signed" / "unsigned"
     audio_type      = bitrate_variable / other_type
     other_type      = alphanumeric
     pos_integer     = 1*DIGIT

   and
     content type is given in the MIME syntax.
 

Example:

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

C. Describing the video or image encodings:

     video_encodings   = video_enc_param *( "&" video_param )
     video_enc_param   = "encoding=" video_enc
     video_enc         = "gray8" / "rgb888" / "bgr888" /
                         "rgb565" / "rgb555" / "yuv444" /
                         "yuv422" / "yuv420" / "jpeg" / "png" /
                         content_type
     video_param       = "width=" width /
                         "height=" height /
                         "fps=" fps /
                         "colors=" colors /
                         "progressive=" progressive /
                         "interlaced=" interlaced /
                         "type=" video_type
     width             = pos_integer
     height            = pos_integer
     fps               = pos_number
     quality           = pos_integer
     colors            = "p" colors_in_palette /
                       = "rgb" r_bits g_bits b_bits /
                       = "gray" gray_bits
     colors_in_palette = pos_integer
     r_bits            = pos_integer
     g_bits            = pos_integer
     b_bits            = pos_integer
     gray_bits         = pos_integer
     progressive       = boolean
     video_type        = jfif / exif / other_type
     other_type        = alphanumeric
     interlaced        = boolean
     pos_number        = 1*DIGIT [ "." 1*DIGIT ]
     boolean           = "true" / "false"

   and
     content type is given in the MIME syntax.
 

Examples:

     encoding=gray8&width=160&height=120
     encoding=jpeg&quality=80&progressive=true&type=jfif
         (progressive JPEG with quality 80 in jfif format)
     encoding=jpeg&type=exif
         (JPEG in exif format)
     encoding=png&colors=rgb888
         (24 bits/pixel PNG)
     encoding=rgb888
         (raw 24-bit rgb image)
     encoding=rgb&colors=rgb888
         (raw 24-bit rgb image)
 

D. Describing mixed audio and video encodings:

     mixed_encodings = audio_encodings "&" video_encodings
 

Example:

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

E. Describing custom media encodings:

     custom_encodings = custom_enc_param *( "&" param )
     custom_enc_param = "encoding=" value
     param            = key "=" value
     key              = alphanumeric
     value            = alphanumeric
 

F. Rules for handling the encodings strings:

• If a given parameter is a custom parameter and is not recognizable by the implementation, the parameter is treated as an illegal parameter and the method must throw an appropriate Exception to denote that.
• If the value for a given parameter is incorrect because it is syntactically wrong or illegal (e.g. out of range), the method must throw an appropriate Exception to denote that.

See Also:

javax.microedition.media.protocol.DataSource, Player, TimeBase

Field Summary

Fields

Modifier and Type	Field and Description
static String	TONE_DEVICE_LOCATOR The locator to create a tone Player to play back tone sequences.

Method Summary

Methods

Modifier and Type	Method and Description
static Player	createPlayer(InputStream stream, String type) Create a Player to play back media from an InputStream.
static Player	createPlayer(String locator) Create a Player from an input locator.
static String[]	getSupportedContentTypes(String protocol) Return the list of supported content types for the given protocol.
static String[]	getSupportedProtocols(String content_type) Return the list of supported protocols given the content type.
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 String TONE_DEVICE_LOCATOR

The locator to create a tone Player to play back tone sequences. For example,

 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.

See Also:

Constant Field Values

Method Detail

getSupportedContentTypes

public static String[] getSupportedContentTypes(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 String[] getSupportedProtocols(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(String locator)
                           throws 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:

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

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

createPlayer

public static Player createPlayer(InputStream stream,
                  String type)
                           throws 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:

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

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

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:

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