def _sampleCalculator(self, channels, pos, sampwidth, factors, attenuator):
"""
Return the sample value, applying a factor and an attenuator.
@param channels (Channel[]) the list of channels
@param pos (int) the position of the sample to calculate
@param sampwidth (int) the sample width
@param factors (float[]) the list of factors to apply to each sample of a channel (1 channel = 1 factor)
@param attenuator (float) a factor to apply to each sum of samples
@return the value of the sample calculated (float)
"""
#variables to compare the value of the result sample to avoid clipping
minval = audioutils.get_minval(sampwidth)
maxval = audioutils.get_maxval(sampwidth)
#the result sample is the sum of each sample with the application of the factors
sum = 0
for factor,channel in zip(factors,channels):
data = channel.frames[pos:pos+sampwidth]
data = unpack_data(data, sampwidth)
# without a cast, sum is a float!
sum += data[0]*factor*attenuator
#truncate the values if there is clipping
if sum < 0:
return max(sum,minval)
elif sum > 0:
return min(sum,maxval)
return 0
if verbose > 0:
p = TextProgress()
p.set_new()
p.set_header("Getting the factor to avoid clipping")
if verbose > 1:
print "\nBegin getting factor at %s"%time.strftime('%d/%m/%y %H:%M:%S',time.localtime())
if p: p.update(0.1, "Left")
maxleft = mixerleft.get_max()
if p: p.update(0.5, "Right")
maxright = mixerright.get_max()
if p: p.update(0.9, "Attenuator estimation")
maxval = max(maxleft, maxright)
maxvalth = audioutils.get_maxval( sampleswidth )
if maxval > maxvalth:
attenuator = float(maxvalth)/maxval*0.95
else:
attenuator = 1
if verbose > 0:
p.update(1, "")
del p
if verbose > 1:
print "\nEnd getting factor at %s"%time.strftime('%d/%m/%y %H:%M:%S',time.localtime())
# what's for????
#attenuator = 1