@@ -478,7 +478,7 @@ def __exit__(self, *args):
478478# User visible methods.
479479#
480480def setnchannels (self ,nchannels ):
481- if self ._datawritten :
481+ if self ._datawritten and self . _nchannels != nchannels :
482482raise Error ('cannot change parameters after starting to write' )
483483if nchannels < 1 :
484484raise Error ('bad # of channels' )
@@ -490,7 +490,7 @@ def getnchannels(self):
490490return self ._nchannels
491491
492492def setsampwidth (self ,sampwidth ):
493- if self ._datawritten :
493+ if self ._datawritten and self . _sampwidth != sampwidth :
494494raise Error ('cannot change parameters after starting to write' )
495495if sampwidth < 1 or sampwidth > 4 :
496496raise Error ('bad sample width' )
@@ -502,19 +502,20 @@ def getsampwidth(self):
502502return self ._sampwidth
503503
504504def setframerate (self ,framerate ):
505- if self ._datawritten :
505+ rounded_framerate = int (round (framerate ))
506+ if self ._datawritten and self ._framerate != rounded_framerate :
506507raise Error ('cannot change parameters after starting to write' )
507- if framerate <= 0 :
508+ if rounded_framerate <= 0 :
508509raise Error ('bad frame rate' )
509- self ._framerate = int ( round ( framerate ))
510+ self ._framerate = rounded_framerate
510511
511512def getframerate (self ):
512513if not self ._framerate :
513514raise Error ('frame rate not set' )
514515return self ._framerate
515516
516517def setnframes (self ,nframes ):
517- if self ._datawritten :
518+ if self ._datawritten and self . _nframes != nframes :
518519raise Error ('cannot change parameters after starting to write' )
519520self ._nframes = nframes
520521
@@ -537,8 +538,8 @@ def getcompname(self):
537538
538539def setparams (self ,params ):
539540nchannels ,sampwidth ,framerate ,nframes ,comptype ,compname = params
540- if self . _datawritten :
541- raise Error ( 'cannot change parameters after starting to write' )
541+ # no check for value change required: either the properties have the same
542+ # value or they throw the exception them selfs
542543self .setnchannels (nchannels )
543544self .setsampwidth (sampwidth )
544545self .setframerate (framerate )