Capturing Audio to Disk
Typically, you
don’t just capture media and immediately dispose of
it—you want to save the media to disk as you capture so that
you can use it later. Fortunately, the
SequenceGrabber
makes this pretty easy.
How do I do that?
Adding to the previous labs’ code, the calls to set
up the SequenceGrabber
need to be changed to
prepare for grabbing to disk. Specifically, the
SGSoundChannel
’s setUsage()
call gets a flag to indicate that it will be
writing the captured audio to disk:
soundChannel.setUsage (StdQTConstants.seqGrabPreview | StdQTConstants.seqGrabRecord);
Next, add a call to give the user an opportunity to configure the audio capture:
soundChannel.settingsDialog( );
Warning
The settingsDialog( )
call will crash Java 1.4.2
on Mac OS X if called from the AWT event-dispatch thread. Yes,
it’s a bug. To work around this until the bug is
fixed, you can stash the call in another thread and block on it. For
instance, in this example you could replace the
settingsDialog( )
call with the following:
final SGSoundChannel sc = soundChannel; Thread t = new Thread( ) { public void run( ) { try { sc.settingsDialog( ); } catch (QTException qte) { qte.printStackTrace( ); } } }; t.start( ); while (t.isAlive( )) Thread.yield( );
After starting the preview, tell the
SequenceGrabber
where it should save the captured
audio:
// create output file grabFile = new QTFile (new java.io.File ("audiograb.mov")); if (grabFile.exists( )) grabFile.delete( ); grabber.setDataOutput(grabFile, ...
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