OSS Audio Device in Python

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If you’ve ever wanted to write some sweet tunes or record some sick beats using Python, this is the article for you.

First things first: what exactly is an OSS audio device? Well, it’s a piece of software that allows you to interact with your computer’s sound card through Python.

Now, Let’s get cracking with the details. To use an OSS audio device in Python, you need to import the ossaudiodev module and create a new object using the open() function:

# Import necessary libraries
import os # Importing the os library to interact with the operating system
from ctypes import * # Importing the ctypes library to access low-level functions
import struct # Importing the struct library to convert between Python values and C structs

# Define a class for the OSS audio device
class OSSAudioDevice(object):
    # Initialize the class with a default device name
    def __init__(self, devname='/dev/dsp'):
        # Use the windll library to call the CreateFileA function from the kernel32 library
        # This function creates a file object for the specified device name
        self.fd = windll.kernel32.CreateFileA(str(devname), 0, 0, None, 3, 0)
        # Check if the file object was successfully created
        if self.fd == -1:
            # If not, raise an exception
            raise Exception("Failed to open OSS audio device")
        # Create variables to store the audio format, number of channels, and sample rate
        self.format = c_uint() # Unsigned integer
        self.channels = c_ushort() # Unsigned short
        self.speed = c_ulonglong() # Unsigned long long
        # Set the output format to signed 16-bit little endian using the setfmt function
        self.setfmt(FORMAT_PCM, 2)
        # Set the number of channels to 2 (stereo)
        self.channels(2)
        # Set the sample rate to 44100 (CD quality audio)
        self.speed(44100)

    # Define a function to set the audio format
    def setfmt(self, format, channels):
        # Use the windll library to call the ioctl function from the fcntl library
        # This function sets the audio format for the specified file object
        windll.fcntl.ioctl(self.fd, SNDCTL_DSP_SETFMT, format)
        # Use the windll library to call the ioctl function again to set the number of channels
        windll.fcntl.ioctl(self.fd, SNDCTL_DSP_CHANNELS, channels)

    # Define a function to close the file object when the class is deleted
    def __del__(self):
        # Use the windll library to call the CloseHandle function from the kernel32 library
        # This function closes the file object
        windll.kernel32.CloseHandle(self.fd)

This code creates a new OSSAudioDevice object with the default device name (/dev/dsp). The constructor sets up some internal variables and calls three methods to set the output format, number of channels, and sample rate.

Now that we have our audio device all set up, let’s write some sweet tunes! To do this, we can use the write() method to send bytes of data to the OSS audio device:

# Constructor to set up internal variables and call methods
def __init__(self):
    self.output_format = None # initialize output format variable
    self.num_channels = None # initialize number of channels variable
    self.sample_rate = None # initialize sample rate variable
    self.set_output_format() # call method to set output format
    self.set_num_channels() # call method to set number of channels
    self.set_sample_rate() # call method to set sample rate

# Method to set output format
def set_output_format(self):
    self.output_format = "OSS" # set output format to OSS

# Method to set number of channels
def set_num_channels(self):
    self.num_channels = 2 # set number of channels to 2

# Method to set sample rate
def set_sample_rate(self):
    self.sample_rate = 44100 # set sample rate to 44100

# Function to play sound by breaking data into smaller chunks and writing to audio device
def play_sound(data):
    for chunk in chunks(data, 1024): # break data into smaller chunks of size 1024
        self.write(chunk) # write each chunk to the audio device

This code takes a byte array of sound data and breaks it up into smaller chunks (to avoid buffer overflows). It then sends each chunk to the OSS audio device using the write() method.

We can also read from the OSS audio device using the read() method:

# This function records sound for a specified duration
def record_sound(duration):
    # Create a buffer to hold recorded sound
    data = bytearray(1024)
    # Loop until we have enough data for our desired recording length (in seconds)
    while len(data) < duration * 1024:
        # Read as much data as possible into the buffer
        num_read = self.read(len(data))
        # Check if there's no more data to be read
        if num_read == 0:
            # Exit loop if we hit end of file or other error condition
            break
        # Append reversed bytes to the buffer (since OSS audio device reads in big-endian format)
        data += memoryview(self.fd.read(num_read))[::-1]

This code creates a byte array to hold our recorded sound, and keeps reading from the OSS audio device until we have enough data for our desired recording length. It then appends each chunk of data to the end of the buffer (in reversed order), since the OSS audio device reads in big-endian format.

And that’s it! With these simple steps, you can now write and record sweet tunes using Python and an OSS audio device. So go ahead let your creativity flow and make some sick beats!

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