#!/usr/bin/env python
# coding: utf-8

# In[1]:


# http://nbviewer.jupyter.org/github/librosa/librosa/blob/master/examples/LibROSA%20demo.ipynb
import librosa
import librosa.display

import IPython.display

get_ipython().run_line_magic('matplotlib', 'inline')
import matplotlib.pyplot as plt
import numpy as np

def player(audio_path):
    return IPython.display.Audio(audio_path)

def spectrogram(audio_path, title):
    y, sr = librosa.load(audio_path, sr=None)
    S = librosa.feature.melspectrogram(y, sr=sr, n_mels=256)
    log_S = librosa.power_to_db(S, ref=np.max)
    plt.figure(figsize=(12,4))
    librosa.display.specshow(log_S, sr=sr, x_axis='time', y_axis='mel', fmax=22050)
    plt.title(title)
    plt.colorbar(format='%+02.0f dB')
    plt.tight_layout()


# ## Opus 16 kbps
# 
# ```console
# $ ffmpeg -i rains.flac -c:a libopus -b:a 16k 16k.opus
# ```

# In[2]:


audio_path = '16k.opus'
player(audio_path)


# In[3]:


spectrogram(audio_path, 'Opus 16kbps')


# ## Opus 8 kbps
# 
# ```console
# $ ffmpeg -i rains.flac -c:a libopus -b:a 8k 8k.opus
# ```

# In[4]:


audio_path = '8k.opus'
player(audio_path)


# In[5]:


spectrogram(audio_path, 'Opus 8kbps')


# ## Opus 4 kbps
# 
# ```console
# $ ffmpeg -i rains.flac -c:a libopus -b:a 4k 4k.opus
# ```

# In[6]:


audio_path = '4k.opus'
player(audio_path)


# In[7]:


spectrogram(audio_path, 'Opus 4kbps')


# ## Opus 2 kbps
# 
# ```console
# $ ffmpeg -i rains.flac -c:a libopus -b:a 2k 2k.opus
# ```

# In[8]:


audio_path = '2k.opus'
player(audio_path)


# In[9]:


spectrogram(audio_path, 'Opus 2kbps')