def main(source, target='', pca='', start=0, seconds=10.):
b = audio.Builder()
mels = b.read(source, pca, start, seconds)
if b.log:
mels = np.exp(mels)
# reconstruct the linearly-spaced spectrum by inverting the triangular
# mel-spaced filterbank. since the filterbank converter is a rectangular
# matrix, this will inevitably result in some loss, but by keeping the
# number of mel filters relatively large we can minimize that loss.
filters, _ = mel.filterbank(b.width // 2 + 1, mels.shape[1])
finv = np.linalg.pinv(filters)
mags = np.dot(mels, finv)
logging.info('inverting mels %s x inverse %s => mags %s',
mels.shape, finv.shape, mags.shape)
#lmj.plot.axes(211, spines=False).imshow(np.log(mels).T, origin='lower')
#lmj.plot.axes(212, spines=False).imshow(np.log(mags).T, origin='lower')
#lmj.plot.show()
b.reconstruct(mags)
b.write(target or source.replace('.npy', '.wav'))
