Audio Frequency in Python

Question

I have made a script which checks the frequency of the sound from a wave file. But I keep getting an error in the 24 line which is while len(data) == chunk*swidth: . Can anyone help me ?? I am using PyAudio, wave and Numpy to do this.

# Read in a WAV and find the freq's
import pyaudio
import wave
import numpy as np

chunk = 2048

# open up a wave
wf = wave.open('output.wav', 'rb')
swidth = wf.getsampwidth()
RATE = wf.getframerate()
# use a Blackman window
window = np.blackman(chunk)
# open stream
p = pyaudio.PyAudio()
stream = p.open(format =
                p.get_format_from_width(wf.getsampwidth()),
                channels = wf.getnchannels(),
                rate = RATE,
                output = True)

# read some data data = wf.readframes(chunk)
# play stream and find the frequency of each chunk
while len(data) == chunk*swidth:
    # write data out to the audio stream
    stream.write(data)
    # unpack the data and times by the hamming window
    indata = np.array(wave.struct.unpack("%dh"%(len(data)/swidth),\
                                         data))*window
    # Take the fft and square each value
    fftData=abs(np.fft.rfft(indata))**2
    # find the maximum
    which = fftData[1:].argmax() + 1
    # use quadratic interpolation around the max
    if which != len(fftData)-1:
        y0,y1,y2 = np.log(fftData[which-1:which+2:])
        x1 = (y2 - y0) * .5 / (2 * y1 - y2 - y0)
        # find the frequency and output it
        thefreq = (which+x1)*RATE/chunk
        print ("The freq is %f Hz." % (thefreq))
    else:
        thefreq = which*RATE/chunk
        print ("The freq is %f Hz." % (thefreq))
    # read some more data
    data = wf.readframes(chunk)
if data:
    stream.write(data)
stream.close()
p.terminate()

This is the error message Traceback (most recent call last): File "C:\\Users\\Admin\\Desktop\\Ishan\\Python\\Sublime Text Projects\\Sound Frequencies second.py", line 23, in <module> while len(data) == chunk*swidth: NameError: name 'data' is not defined

Answer 1

you use data in while, which defined later. use flag in while with post check, whittled preset as True to start while 1st round:

# Read in a WAV and find the freq's
import pyaudio
import wave
import numpy as np

chunk = 2048

# open up a wave
wf = wave.open('output.wav', 'rb')
swidth = wf.getsampwidth()
RATE = wf.getframerate()
# use a Blackman window
window = np.blackman(chunk)
# open stream
p = pyaudio.PyAudio()
stream = p.open(format =
                p.get_format_from_width(wf.getsampwidth()),
                channels = wf.getnchannels(),
                rate = RATE,
                output = True)

# play stream and find the frequency of each chunk

flag = True # << define flag and set to True to make while 1st stap

while flag:

    # read some data << move under while to this plase
    data = wf.readframes(chunk)

    # write data out to the audio stream
    stream.write(data)
    # unpack the data and times by the hamming window
    indata = np.array(wave.struct.unpack("%dh"%(len(data)/swidth),\
                                         data))*window
    # Take the fft and square each value
    fftData=abs(np.fft.rfft(indata))**2
    # find the maximum
    which = fftData[1:].argmax() + 1
    # use quadratic interpolation around the max
    if which != len(fftData)-1:
        y0,y1,y2 = np.log(fftData[which-1:which+2:])
        x1 = (y2 - y0) * .5 / (2 * y1 - y2 - y0)
        # find the frequency and output it
        thefreq = (which+x1)*RATE/chunk
        print ("The freq is %f Hz." % (thefreq))
    else:
        thefreq = which*RATE/chunk
        print ("The freq is %f Hz." % (thefreq))
    # read some more data
    # data = wf.readframes(chunk) << comment this line

    if (len(data) != chunk*swidth): # << put check while condition
        flag=False

if data:
    stream.write(data)
# ^^^ I think you need to put in to the while loop upper

stream.close()
p.terminate()

I didn't watch working capacity as a whole, and only logical mistake at this stage with the cycle while and an entry condition.