Im trying to identify the musical note of a sound from a .wav file using python, but im getting the error above when using "struct" I couldn't gather a lot of info from the documents for struct or other websites on how to resolve this issue.
I have seen errors like:
struct.error: unpack requires a buffer of 4 bytes
struct.error: unpack requires a buffer of 1024 bytes
but the error seems to be for a different reason.
import numpy as np
import math
import wave
import os
import struct
import matplotlib.pyplot as plt
def note_detect(audio_file):
#-------------------------------------------
#here we are just storing our sound file as a numpy array
#you can also use any other method to store the file as an np array
file_length=audio_file.getnframes()
f_s=audio_file.getframerate() #sampling frequency
sound = np.zeros(file_length) #blank array
for i in range(file_length) :
wdata=audio_file.readframes(1)
data=struct.unpack("<h",wdata)
sound[i] = int(data[0])
plt.plot(sound)
plt.show()
sound=np.divide(sound,float(2**15)) #scaling it to 0 - 1
counter = audio_file.getnchannels() #number of channels mono/sterio
#-------------------------------------------
plt.plot(sound)
plt.show()
#fourier transformation from numpy module
fourier = np.fft.fft(sound)
fourier = np.absolute(fourier)
imax=np.argmax(fourier[0:int(file_length/2)]) #index of max element
plt.plot(fourier)
plt.show()
#peak detection
i_begin = -1
threshold = 0.3 * fourier[imax]
for i in range (0,imax+100):
if fourier[i] >= threshold:
if(i_begin==-1):
i_begin = i
if(i_begin!=-1 and fourier[i]<threshold):
break
i_end = i
imax = np.argmax(fourier[0:i_end+100])
freq=(imax*f_s)/(file_length*counter) #formula to convert index into sound frequency
#frequency database
note=0
name = np.array(["C0","C#0","D0","D#0","E0","F0","F#0","G0","G#0","A0","A#0","B0","C1","C#1","D1","D#1","E1","F1","F#1","G1","G#1","A1","A#1","B1","C2","C#2","D2","D#2","E2","F2","F#2","G2","G2#","A2","A2#","B2","C3","C3#","D3","D3#","E3","F3","F3#","G3","G3#","A3","A3#","B3","C4","C4#","D4","D4#","E4","F4","F4#","G4","G4#","A4","A4#","B4","C5","C5#","D5","D5#","E5","F5","F5#","G5","G5#","A5","A5#","B5","C6","C6#","D6","D6#","E6","F6","F6#","G6","G6#","A6","A6#","B6","C7","C7#","D7","D7#","E7","F7","F7#","G7","G7#","A7","A7#","B7","C8","C8#","D8","D8#","E8","F8","F8#","G8","G8#","A8","A8#","B8","Beyond B8"])
frequencies = np.array([16.35,17.32,18.35,19.45,20.60,21.83,23.12,24.50,25.96 ,27.50 ,29.14 ,30.87 ,32.70 ,34.65 ,36.71 ,38.89 ,41.20 ,43.65 ,46.25 ,49.00 ,51.91 ,55.00 ,58.27 ,61.74 ,65.41 ,69.30 ,73.42 ,77.78 ,82.41 ,87.31 ,92.50 ,98.00 ,103.83 ,110.00 ,116.54 ,123.47 ,130.81 ,138.59 ,146.83 ,155.56 ,164.81 ,174.61 ,185.00 ,196.00 ,207.65 ,220.00 ,233.08 ,246.94 ,261.63 ,277.18 ,293.66 ,311.13 ,329.63 ,349.23 ,369.99 ,392.00 ,415.30 ,440.00 ,466.16 ,493.88 ,523.25 ,554.37 ,587.33 ,622.25 ,659.26 ,698.46 ,739.99 ,783.99 ,830.61 ,880.00 ,932.33 ,987.77 ,1046.50 ,1108.73 ,1174.66 ,1244.51 ,1318.51 ,1396.91 ,1479.98 ,1567.98 ,1661.22 ,1760.00 ,1864.66 ,1975.53 ,2093.00 ,2217.46 ,2349.32 ,2489.02 ,2637.02 ,2793.83 ,2959.96 ,3135.96 ,3322.44 ,3520.00 ,3729.31 ,3951.07 ,4186.01 ,4434.92 ,4698.64 ,4978.03 ,5274.04 ,5587.65 ,5919.91 ,6271.93 ,6644.88 ,7040.00 ,7458.62 ,7902.13,8000])
#searching for matched frequencies
for i in range(0,frequencies.size-1):
if(freq<frequencies[0]):
note=name[0]
break
if(freq>frequencies[-1]):
note=name[-1]
break
if freq>=frequencies[i] and frequencies[i+1]>=freq :
if freq-frequencies[i]<(frequencies[i+1]-frequencies[i])/2 :
note=name[i]
else :
note=name[i+1]
break
return note
if __name__ == "__main__":
path = os.getcwd()
file_name = path + "\\" + "recording0.wav"
audio_file = wave.open(file_name)
Detected_Note = note_detect(audio_file)
print("\n\tDetected Note = " + str(Detected_Note))
The full error on line 23:
Traceback (most recent call last):
File "C:\Users\m8\Desktop\programing_stuff\python-stuff\minecraft_flute_player - 12-08-2022\app.py", line 86, in <module>
Detected_Note = note_detect(audio_file)
File "C:\Users\m8\Desktop\programing_stuff\python-stuff\minecraft_flute_player - 12-08-2022\app.py", line 23, in note_detect
data=struct.unpack("<h",wdata)
struct.error: unpack requires a buffer of 2 bytes
Thanks for the help.
What I assume is happening here is the size of the frame isn't 2 bytes as you expected.
When stating <h you are stating that you are going to extract 2 bytes from each frame. See the stuct documentation for more on that.
You can use the getparams function to better understand the structure of the wav file.
>>> audio_file.getparams()
_wave_params(nchannels=1, sampwidth=2, framerate=44100, nframes=22050, comptype='NONE', compname='not compressed')
The parameters which are interesting are nchannels and sampwidth.
You can calculate sampwidth * nchannels to understand the amount of bytes you need to extract from the frame for this WAV file.
In this example, you have sampwidth * nchannels = 1 * 2 = 2 bytes per frame.
More information can be found in this answer which shows different cases of frame sizes.