Java How to Program Fourth Edition - DCC

Chapter 22 Java Media Framework and Java Sound (on CD) 1263
ponent to obtain the GUI component that displays the monitored media. MonitorControls
typically have a checkbox to enable or disable displaying media. Also, audio
devices have a volume control and video devices have a control for setting the preview
frame rate. Line 301 invokes method showSaveMonitor (lines 245–261) to display the
monitoring GUI in a dialog box. To terminate capturing, users can press the OK button or
close the dialog box (lines 254–261). For some video capture devices, the Processor
needs to be in a Stopped state to enable monitoring of the saving and capturing process.
Thus far, we have discussed JMF’s capabilities to access, present and save media content.
Our final JMF example demonstrates how to send media between computers using
JMF’s streaming capabilities.
22.4 RTP Streaming
Streaming media refers to media that is transferred from a server to a client in a continuous
stream of bytes. The client can begin playing the media while still downloading the media
from the server. Audio and video media files are often many megabytes in size. Live events,
such as concerts or football game broadcasts, may have indeterminable sizes. Users could
wait until a recording of a concert or game is posted, then download the entire recording.
However, at today’s Internet connection speeds, downloading such a broadcast could take
days and typically users prefer to listen to live broadcasts as they occur. Streaming media
enables client applications to play media over the Internet or over a network without downloading
the entire media file at once.
In a streaming media application, the client typically connects to a server that sends a
stream of bytes containing the media back to the client. The client application buffers (i.e.
stores locally) a portion of the media, which the client begins playing after a certain portion
has been received. The client continually buffers additional media, providing users with an
uninterrupted clip, as long as network traffic does not prevent the client application from
buffering additional bytes. With buffering, users experience the media within seconds of
when the streaming begins, even though all of the material has not been received.
Performance Tip 22.3
Streaming media to a client enables the client to experience the media faster than if the client
must wait for an entire media file to download. 22.3
Demand for real-time, robust multimedia is rising dramatically as the speed of Internet
connections increase. Broadband Internet access, which provides high-speed network connections
to the Internet for so many home users, is becoming more popular, though the
number of users remains relatively small compared to the total number of Internet users.
With faster connections, streaming media can provide a better multimedia experience.
Users with slower connections can still experience the multimedia, though with lesser
quality. The wide range of applications that use streaming media is growing. Applications
that stream video clips to clients have expanded to provide real-time broadcast feeds. Thousands
of radio stations stream music continuously over the Internet. Client applications
such as RealPlayer have focused on streaming media content with live radio broadcasts.
Applications are not limited to audio and video server-to-client streaming. For example,
teleconferencing and video conferencing applications increase efficiency in everyday business
by reducing the need for business people to travel great distances to attend meetings.