Python binding allowing to retrieve audio levels by frequency bands given audio samples, on a raspberry pi (aka power spectrum). It uses the GPU FFT lib (see http://www.aholme.co.uk/GPU_FFT/Main.htm).
I compared implementations using cython and ctypes, and the ctypes solution was slower (overhead due to the input data transformation for the C call).
In my case it's 7 times faster than using pure python with Numpy.
The GPU FFT lib sources which can be found here http://www.aholme.co.uk/GPU_FFT/Main.htm. It is also directly in raspbian. You will also need Cython.
$ python setup.py build_ext --inplace
This generates the rpi_audio_levels.so, be sure to add its directory to the PYTHONPATH
(or install it using sudo python setup.py install instead of the above command).
from rpi_audio_levels import AudioLevels
DATA_SIZE = 11 # -> we will give chunks of 2**11 audio samples
BANDS_COUNT = 6 # -> we will give 6 ranges of band indexes for each computation
# Preliminary call to prepare things
audio_levels = AudioLevels(DATA_SIZE, BANDS_COUNT)
# example of 6 arbitrary frequency bands. Indexes must be between 0 and 2**(DATA_SIZE - 1)
bands_indexes = [[0,100], [100,200], [200,600], [600,700], [700,800], [800,1024]]
# Then retrieve audio levels each time you have new data
levels = audio_levels.compute(data, bands_indexes)
# data must be an numpy array of 2**DATA_SIZE real data with float dtype (np.float32), with only 1 dimmension.