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• aubio documentation about initiating a pitch detector, https://aubio.org/doc/latest/pitch_8h.html#a962561ea270e0308ed26ac9bab554550.
• The 1st parameter is the method of the pitch detection. Up to now, I only know "DEFAULT" method. I am not sure if there is other methods and if those other methods better for my case. Nevertheless, I will keep using "DEFAULT" for now on.
• The 2nd parameter is a buffer before the sound sent to be processed.
• The 3rd parameter is said to be the interval between two consecutive sound analysis. The variable used is called hop_size. Other than these, I am not sure on what does this parameter do.
  • In the example code hop_size is buffer divided by 2 and rounded up.
• The last parameter is the sample size. I do not know what does sample size do.

• This website shows an example of initiating alsaaudio PCM object in Python, http://larsimmisch.github.io/pyalsaaudio/libalsaaudio.html?highlight=alsaaudio.pcm#alsaaudio.PCM.
• alsaaudio PCM object can be used to either read or record/stream from microphone.
• Because I am going to use alsaaudio for audio recording I need to set type = alsaaudio.PCM_CAPTURE.
• Here is an example of code of my alsaaudio object in Python.

self.recorder = alsaaudio.PCM(
    type = alsaaudio.PCM_CAPTURE
)

• PCM.read() returns a length and data tuple, http://larsimmisch.github.io/pyalsaaudio/libalsaaudio.html?highlight=alsaaudio.pcm#alsaaudio.PCM.

• I was wondering what does PCM means. PCM means Pulse-code Modulation. PCM is used to digitally represent analog signals, https://en.wikipedia.org/wiki/Pulse-code_modulation.

• Sharing variable across modules in Python, https://docs.python.org/2/faq/programming.html#how-do-i-share-global-variables-across-modules.
• Example.

#variable.py
variable_text = "Hello world!"

#other.py
import variable
variable.variable_text = variable.variable_text + " Hello world again!"
#This print will result in "Hello world! Hello world again!"
print(variable.variable_text)

• Example of constant in Python. Although, Python has no specific method on how to make constant, http://stackoverflow.com/questions/10672419/class-constants-in-python.

• So, constant can be treated as other normal Python variables. So, make sure to have use prefix self in variable that is class wide available.
• Screenshot to the StackOverflow Python discussion.

• My Python thread in StackOverflow, http://stackoverflow.com/questions/40686640/alsaaudio-pcm-capture-does-not-work-with-opencvs-cv2-videocapture0-read. Seems there is no one that understand the problem. Although, I think I put too specific title.
• Nevertheless, the problem is now solved by only using face detection in appropriate moment. Before, face detection is always on and it makes the program takes more RAM.
• Here is the screenshot of the thread.

• Example of using global variable in Python, http://stackoverflow.com/questions/423379/using-global-variables-in-a-function-other-than-the-one-that-created-them.
• However, for now I will not using this and use the sharing variable across module.