adds media-related functionality to its superinterface,
. This functionality includes transport-control methods that start, stop, drain, and flush the audio data that passes through the line. A data line can also report the current position, volume, and audio format of the media. Data lines are used for output of audio by means of the subinterfaces
, which allow an application program to write data. Similarly, audio input is handled by the subinterface
, which allows data to be read.
A data line has an internal buffer in which the incoming or outgoing audio data is queued. The
drain() method blocks until this internal buffer becomes empty, usually because all queued data has been processed. The
flush() method discards any available queued data from the internal buffer.
A data line produces
STOP events whenever it begins or ceases active presentation or capture of data. These events can be generated in response to specific requests, or as a result of less direct state changes. For example, if
start() is called on an inactive data line, and data is available for capture or playback, a
START event will be generated shortly, when data playback or capture actually begins. Or, if the flow of data to an active data line is constricted so that a gap occurs in the presentation of data, a
STOP event is generated.
Mixers often support synchronized control of multiple data lines. Synchronization can be established through the
synchronize method. See the description of the
Mixer interface for a more complete description.