Modules/ossaudiodev.c

Source:

cpython 3.14 @ ab2d84fe1023/Modules/ossaudiodev.c ↗

ossaudiodev wraps the Linux Open Sound System (OSS) /dev/dsp audio device. Deprecated in Python 3.11 and removed in 3.13 (OSS itself was superseded by ALSA on Linux).

Map

Lines	Symbol	Role
1-80	oss_open_impl	Open /dev/dsp for read/write
81-200	oss_read_impl / oss_write_impl	Read/write raw PCM samples
201-350	oss_setfmt	Set sample format (AFMT_S16_LE, etc.)
351-500	oss_channels	Set mono/stereo channel count
501-650	oss_speed	Set sample rate
651-800	Mixer API	/dev/mixer volume and source controls

Reading

oss_open_impl

// CPython: Modules/ossaudiodev.c:88 oss_open_impl
static PyObject *
oss_open_impl(PyTypeObject *type, const char *device, int mode)
{
    /* device defaults to /dev/dsp; mode: O_RDONLY, O_WRONLY, O_RDWR */
    int fd = open(device ? device : "/dev/dsp", mode);
    if (fd < 0)
        return PyErr_SetFromErrnoWithFilename(PyExc_OSError, device);
    OSSAudioObject *self = PyObject_New(OSSAudioObject, type);
    self->fd   = fd;
    self->mode = mode;
    return (PyObject *)self;
}

oss_read_impl

// CPython: Modules/ossaudiodev.c:180 oss_read_impl
static PyObject *
oss_read_impl(OSSAudioObject *self, int size)
{
    PyObject *rv = PyBytes_FromStringAndSize(NULL, size);
    Py_BEGIN_ALLOW_THREADS
    int nread = read(self->fd, PyBytes_AS_STRING(rv), size);
    Py_END_ALLOW_THREADS
    if (nread < 0) {
        Py_DECREF(rv);
        return PyErr_SetFromErrno(PyExc_OSError);
    }
    _PyBytes_Resize(&rv, nread);
    return rv;
}

Setting sample format

// CPython: Modules/ossaudiodev.c:260 oss_setfmt_impl
/* AFMT_S16_LE: 16-bit signed little-endian
   AFMT_U8:     8-bit unsigned
   AFMT_S8:     8-bit signed
   AFMT_MU_LAW: mu-law encoding */
static PyObject *
oss_setfmt_impl(OSSAudioObject *self, int val)
{
    if (ioctl(self->fd, SNDCTL_DSP_SETFMT, &val) == -1)
        return PyErr_SetFromErrno(PyExc_OSError);
    return PyLong_FromLong(val);
}

Mixer API

// CPython: Modules/ossaudiodev.c:700 OssMixerObject
/* /dev/mixer controls: SOUND_MIXER_VOLUME, SOUND_MIXER_PCM, etc.
   get(control) → (left, right) 0-100
   set(control, (left, right)) */

gopy notes

ossaudiodev was removed in Python 3.13 and is not in gopy's stdlib. Modern Linux audio uses ALSA via ctypes or sounddevice. The annotation is for historical completeness.