def extract_channel_fragment(channel, fromtime, totime, silence=0.):
"""
Extract a fragment of a channel in the interval [fromtime,totime].
Eventually, surround it by silences.
@param channel (Channel - IN)
@param fromtime (float - IN) From time value in seconds.
@param totime (float - IN) To time value in seconds.
@param silence (float - IN) Duration value in seconds.
"""
framerate = channel.get_framerate()
# Extract the fragment of the channel
startframe = int(fromtime*framerate)
toframe = int(totime*framerate)
fragmentchannel = channel.extract_fragment(begin=startframe, end=toframe)
# Get all the frames of this fragment
nbframes = fragmentchannel.get_nframes()
cf = ChannelFrames( fragmentchannel.get_frames( nbframes ) )
# surround by silences
if silence > 0.:
cf.prepend_silence( silence*framerate )
cf.append_silence( silence*framerate )
return Channel( 16000, 2, cf.get_frames() )
def test_CreateSilence(self):
self._sample_1.extract_channel(0)
self._sample_2.extract_channel(0)
channel = self._sample_1.get_channel(0)
monofrag = ChannelFrames(channel.frames)
monofrag.append_silence(1000)
self.assertEqual(channel.get_nframes()+1000, len(monofrag.get_frames())/channel.get_sampwidth())
def norm_length(self):
"""
Normalize the number of frames of all the channels by appending silence at the end.
"""
nframes = 0
for i in xrange(len(self.channels)):
nframes = max(nframes, self.channels[i].get_nframes())
for i in xrange(len(self.channels)):
if self.channels[i].get_nframes() < nframes:
fragment = ChannelFrames(self.channels[i].frames)
fragment.append_silence(nframes - self.channels[i].get_nframes())
self.channels[i] = Channel(self.channels[i].get_framerate(), self.channels[i].get_sampwidth(), fragment.get_frames())