Sun audio blocks, even when run in a thread

[Bruce Bon]

The class below is intended to play a Sun audio file (.au) in the
background while the main thread, which is servicing a GUI, continues
without impact.  It doesn't work.  For a sound file that takes 3-5
seconds to play, the main thread hangs for that long.  I have run this
many times, with changes in printouts and insertion of strategic
sleeps to try to make sure that the player thread gives up control,
but apparently the call to audioObj.write( audioString ) is atomic --
NOTHING happens in the  main thread until it returns.  I have tested
this with print statements and sleeps in the main thread instead of a
GUI, and you can see the program's output simply halt while the sound
is audible.  I have also looked for delays at dataLock.acquire() and
not found any.

Help, suggestions, explanation or work-around??

Thanks.

                Bruce Bon

_______________________________

import time
import sunaudiodev
from thread import *

class AudioPlayer:

    def __init__( self, owner ):
        '''Constructor.'''
        self.soundQueue = []
        self.terminateFlag = False
        self.dataLock = allocate_lock()
        print 'AudioPlayer:  starting playerThread...'
        print '              main thread ID = ', get_ident()
        self.playerThread = start_new_thread( self.__playerThread, ()
)
        

    def playAudio( self, audio ):
        self.dataLock.acquire()
        self.soundQueue.append( audio ) # put to end of list
        self.dataLock.release()

    def terminate( self ):
        self.dataLock.acquire()
        self.terminateFlag = True
        self.dataLock.release()
        time.sleep(1)

    def __playerThread( self ):
        '''Function to be executed in background thread, to play
sounds.'''
        print '__playerThread() starting: ID = ', get_ident()
        while True:    
            # Check terminateFlag and soundQueue
            audio = None
            self.dataLock.acquire()
            if self.terminateFlag:
                self.dataLock.release()
                print '__playerThread(): terminating playerThread...'
                exit()
            l = len(self.soundQueue)
            if  l > 0:
                audio = self.soundQueue.pop(0)  # get from beginning
of list
            self.dataLock.release()

            if  audio == None:
                time.sleep( 1.0 )               # poll queue 1/second
            else:
                # Read the .au file
                auReadObj = open( audio, 'r' )
                audioString = auReadObj.read()
                auReadObj.close()

                # Open the audio device and play the sound
                try:
                    audioObj = sunaudiodev.open('w')
                except sunaudiodev.error:
                    print 'ERROR __playerThread:  ' + \
                                'Failed to open Sun audio device.'
                else:
                    audioObj.write( audioString )
                    audioObj.close()