A standard Python 2.6+ LF Audio Oscilloscope.

Bazza — Wed Apr 06, 2011 10:41 pm

Author: Bazza

Posted: Wed Apr 06, 2011 10:41 pm

Hi all...

I think this may well be a first for both Python and LXF.

I am building a kids level seismometer and wanted to use standard Python
inside Linux.

This DEMO code was my starter idea and looks as though using standard
ASCII only might just work a real treat.

I've issued it to LXF under the MIT licence for future reasons.

It doesn't look much on screen except that the waveform(s) shown is/are a
crude electrical representation of your voice. ;o)

It is possible to link the earphone socket on this notebook to the mic
input and start the Audio Function Generator, elsewhere in this forum,
in a separate Python terminal and see those waveforms inside the
AudioScope.py`s own Python terminal.

Enjoy finding simple solutions to often very difficult problems.

Be aware of wordwrapping, etc...

Code:

#!/usr/bin/python
#
# AudioScope.py
#
# DEMO LF Audio Oscilloscope using /dev/dsp inside Linux.
# Original copyright, (C)2011, B.Walker, G0LCU.
# Issued to LXF under the MIT licence.
#
# The timebase runs vertically and the waveform amplitude horizontally.
# It grabs a sample for about 1 second and displays the results AFTER
# the sample; technically a basic LF Storage Audio Oscilloscope.
#
# The display only uses standard ASCII characters.
#
# To run just type from the prompt ">>>"...
# >>> execfile("/full/path/to/AudioScope.py")<RETURN/ENTER>
#
# Tested on Python 2.6.x only but should work on other versions of 2.x.x.
# Ensure /dev/dsp exists; if not install oss-compat from your distro`s
# repository. Also ensure the sound card is not already in use.
#
# Enjoy finding simple solutions to often very difficult problems... ;o)
#
# If you are just trying this out and have an internal mic, just talk
# loudly into the microphone and see your vocal wavefrom on screen...
# Needless to say using the external microphone input as an input this
# becomes a single channel uncalibrated LF Audio Oscilloscope.
#
# Press Ctrl-C to STOP.

# Import any necessary modules.
import os

# Do a basic screen clear.
os.system("clear")
# Turn the cursor off to look prettier... ;o)
os.system("setterm -cursor off")

def main():
# Set special variables global.
global audioscope
global chardisplay
global offset
global timebase
global record

# Known variables.
audioscope = 0
chardisplay = "(C)2011, B.Walker, G0LCU."
offset = 0
timebase = 1
record = "Initial issue to LXF under the MIT licence"

# Throw away local variables.
n = 0

while 1:
   # Sample the microphone/external_microphone_input for approximately 1 second.
   audio = file('/dev/dsp', 'rb')
   record = audio.read(8192)
   audio.close()

   # This value points to a character in the 8192 byte string.
   # "offset" can be any value from 0 to 191.
   offset = 0
   # Start the loop from character at position 0.
   while offset <= 8191:
      # Convert the character to a decimal number.
      audioscope = ord(record[offset])
      # Now convert to 6 bit depth to fit one terminal line.
      audioscope = int(audioscope/4)
      # This should never occur but don`t allow an error.
      if audioscope >= 63: audioscope = 63
      if audioscope <= 0: audioscope = 0
      # Invert to correct the trace shown.
      audioscope = 63 - audioscope

      # Loop count to get the correct position to print the plot.
      n = 0
      # Set the trace position for each line and......
      chardisplay = " "
      while n <= audioscope:
         # ......add the required spaces until completed then......
         chardisplay = chardisplay + " "
         n = n + 1
      # ......print the plot point using *.
      print chardisplay + "*"
      # Point to the next character to character in the 8192 string.
      # "timebase" can be any value from 1 to 360.
      offset = offset + timebase

# Assuming a Ctrl-C arrives here enable the cursor again.
os.system("setterm -cursor off")

main()

# End of DEMO.
# Enjoy finding simple solutions to often very difficult problems.

Linux Format forums

A standard Python 2.6+ LF Audio Oscilloscope.