Ch. 10 – Physical

Figure 10.3. Waveform, loudness, and onset strengths (black curve) and estimated beats (dashed lines) of the intro to Help! by The Beatles.

Libraries

Show the code 
import numpy as np
import librosa
import librosa.display
import IPython.display as ipd
from matplotlib import pyplot as plt

1. Read audio file

x, sr = librosa.load('data/help.mp3', offset=1.05, duration=10.087)
ipd.display(ipd.Audio(data=x, rate=sr))

2. Plot waveform

fig, ax = plt.subplots(nrows=1,figsize=(7.5, 2.75))
librosa.display.waveshow(x, sr=sr, ax=ax, color='indigo')

ax.set_title("Waveform")
ax.set_xlabel("Time (s)")
ax.set_ylabel("Amplitude")
ax.set_xticks(range(0, 11, 1))
ax.set_xlim([0, 10])
ax.grid()
fig.tight_layout()
plt.show()

3. Plot loudness

fig, ax = plt.subplots(nrows=1, figsize=(7.5, 2.75))
rms = librosa.feature.rms(y=x)                 # Extra dynamics (RMS)
db = librosa.amplitude_to_db(rms, ref=np.max)   # Convert into dB. Note that this is a relative measure (loudest is now 0) 
times = librosa.times_like(rms)

ax.plot(times, db[0], color='darkblue')
ax.set_title("Loudness")
ax.set_ylim([-15,0])
ax.set_ylabel("Decibel")
ax.set_xlabel("Time (s)")
ax.set_xticks(range(0, 11, 1))
ax.set_xlim([0, 10])
ax.grid()
fig.tight_layout()
plt.show()

4. Plot onset strength, estimated and annotated beats

fig, ax = plt.subplots(nrows=1, figsize=(7.5, 2.75))


onset_subbands = librosa.onset.onset_strength_multi(y=x, 
                                                    sr=sr, 
                                                    channels=[0, 32, 64, 96, 128])

onset_subbands_s = sum(onset_subbands, 1)
ax.plot(times, onset_subbands_s, 'maroon')

tempo, beats = librosa.beat.beat_track(y=x, sr=sr, trim=False)
plt.vlines(times[beats], 0, onset_subbands_s.max(), color='0.40', alpha=0.80,
           linestyle='--', label='Beats')

o_env = librosa.onset.onset_strength(y=x, sr=sr)
times = librosa.times_like(o_env, sr=sr)
onset_frames = librosa.onset.onset_detect(onset_envelope=o_env, sr=sr)

ax.set_title("Onset strength and estimated beats")
ax.set_ylabel("Strength")
ax.set_xlabel("Time (s)")
ax.set_ylim([0, 60])
ax.set_xticks(range(0, 11, 1))
ax.set_xlim([0, 10])
ax.grid()
fig.tight_layout()

data = np.loadtxt('data/Help_beats.csv')  
ann_time = data[0:16, 0]-1.05
ann_label = data[0:16, 1]
for x in range(16):
    ax.text(ann_time[x], 53, int(ann_label[x]), size=6, 
            backgroundcolor='0.8', weight='bold', ha='center')

plt.show()

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