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@dbrady
Created Nov 12, 2010
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Interleaved Unpacking...
# This takes about 2s for a 53Mb file.
bytes = audio_file.read_into(audio_buffer)
# This takes less than a second, BUT the data is interleaved
# (left, right, left, right, left, right, etc)
self.audio_data = audio_buffer.unpack('s*')
# Less than a second.
self.left_channel = NArray.float(2, audio_data.size)
self.right_channel = NArray.float(2, audio_data.size)
# This loop takes about 40-50 seconds. Rewriting it to eliminate
# all division and multiplication shaves about 10s off that time.
0.upto(audio_data.size/2-1) do |i|
time = i.to_f / audio_file.rate
# First array stores time offset of sample
left_channel[0, i] = time
right_channel[0, i] = time
# Second array stores sampled data
left_channel[1, i] = audio_data[i*2]
right_channel[1, i] = audio_data[i*2+1]
end
# BUT!
#
# If I could avoid the Ruby loop altogether, and let something
# like NArray's constructors handle it, it's a 10x speedup. For
# example:
#
# interleaved_data = NArray[self.audio_data]
#
# Takes less than 4 seconds! This is because we're not looping in
# Ruby, but letting C handle the grindy stuff. However, the data
# is interleaved, making it useless for processing rationally. :-/
# I can separate it back out with another loop, but guess how long
# that takes....
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