Rendering Multimedia Content - Beginning Java ME Platform - page 441

Controlling the Rendering Process

For all but the simplest of media players, you will want to have additional control over
media playback. While the Player interface itself lets you start and stop playback, you can
do a lot more by obtaining instances of specific Control subclasses that let you change the
Player 's behavior. To get an instance of a specific kind of control, you pass the name of
the desired class (with the package name, if it's not javax.microedition.media.control )to
the Player 's getControl method, like this:

VolumeControl vc = (VolumeControl)player.getControl("VolumeControl");

Each Control subclass has different methods, reflecting the kind of control over the
media rendering process it offers. Table 16-3 describes some Control subinterfaces that
come in handy when writing multimedia applications. Of course, not every subinterface
is available for a Player instance rendering every media type; it would make little sense,
for example, to be able to obtain a VideoControl for an audio file, or a TempoControl for a
video file.

Table 16-3. Implementors of Control You Can Use to Control Media Rendering

Interface Purpose Example Methods

FramePositioningControl Seek to a specific video frame seek

skip
mapFrameToTime
mapTimeToFrame

GUIControl initDisplayMode Provide an object to render the

media to the GUI

MetaDataControl getKeys

getKeyValue

Obtain metadata in a media file

MIDIControl

Controlling an internal synthesizer various

PitchControl getMaxPitch

Shift pitch of synthesized or sampled

getMinPitch
getPitch
setPitch

audio without changing playback speed

RateControl getMaxRate

getMinRate
getRate
setRate

Shift playback rate

RecordControl commit

setRecordLocation
setRecordStream
startRecord
stopRecord

Record media from a player