#! /usr/bin/env python # Implementation of the timescale algorithm according to Dan Ellis, *A Phase# Vocoder in Matlab*.  http://www.ee.columbia.edu/~dpwe/resources/matlab/pvoc/ # This file follows the original implementation, with analysis in a first pass,# and synthesis in a second pass. import sysfrom aubio import source, sink, pvoc, cvecfrom aubio import unwrap2pi, float_typeimport numpy as np win_s = 1024hop_s = win_s // 8 # 87.5 % overlap warmup = win_s // hop_s - 1 if len(sys.argv) < 3:    print("Usage: {:s} <source_filename> <output_filename> <rate> [samplerate]".format(sys.argv[0]))    print("""Examples:    # twice faster    {0} track_01.mp3 track_01_faster.wav 2.0    # twice slower    {0} track_02.flac track_02_slower.wav 0.5    # one and a half time faster, resampling first the input to 22050    {0} track_02.flac track_02_slower.wav 1.5 22050""".format(sys.argv[0]))    sys.exit(1) source_filename = sys.argv[1]output_filename = sys.argv[2]rate = float(sys.argv[3]) samplerate = 0 if len(sys.argv) < 5 else int(sys.argv[4])source_in = source(source_filename, samplerate, hop_s)samplerate = source_in.sampleratep = pvoc(win_s, hop_s) # allocate memory to store norms and phasesn_blocks = source_in.duration // hop_s + 1# adding an empty frame at end of spectrogramnorms  = np.zeros((n_blocks + 1, win_s // 2 + 1), dtype = float_type)phases = np.zeros((n_blocks + 1, win_s // 2 + 1), dtype = float_type) block_read = 0while True:    # read from source    samples, read = source_in()    # compute fftgrain    spec = p(samples)    # store current grain    norms[block_read] = spec.norm    phases[block_read] = spec.phas    # until end of file    if read < hop_s: break    # increment block counter    block_read += 1 # just to make sure#source_in.close() sink_out = sink(output_filename, samplerate) # interpolated time steps (j = alpha * i)steps = np.arange(0, n_blocks, rate, dtype = float_type)# initial phasephas_acc = phases[0]# excepted phase advance in each binphi_advance = np.linspace(0, np.pi * hop_s, win_s / 2 + 1).astype (float_type) new_grain = cvec(win_s) for (t, step) in enumerate(steps):     frac = 1. - np.mod(step, 1.0)    # get pair of frames    t_norms = norms[int(step):int(step+2)]    t_phases = phases[int(step):int(step+2)]     # compute interpolated frame    new_grain.norm = frac * t_norms[0] + (1. - frac) * t_norms[1]    new_grain.phas = phas_acc    #print t, step, new_grain.norm    #print t, step, phas_acc     # psola    samples = p.rdo(new_grain)    if t > warmup: # skip the first few frames to warm up phase vocoder        # write to sink        sink_out(samples, hop_s)     # calculate phase advance    dphas = t_phases[1] - t_phases[0] - phi_advance    # unwrap angle to [-pi; pi]    dphas = unwrap2pi(dphas)    # cumulate phase, to be used for next frame    phas_acc += phi_advance + dphas for t in range(warmup + 1): # purge the last frames from the phase vocoder    new_grain.norm[:] = 0    new_grain.phas[:] = 0    samples = p.rdo(new_grain)    sink_out(samples, read if t == warmup else hop_s) # just to make sure#sink_out.close() format_out = "read {:d} blocks from {:s} at {:d}Hz and rate {:f}, wrote {:d} blocks to {:s}"print (format_out.format(block_read, source_filename, samplerate, rate,    len(steps), output_filename))