pyalsaaudio/alsaaudio.c

/*
 * alsaaudio -- Python interface to ALSA (Advanced Linux Sound Architecture).
 *              The standard audio API for Linux since kernel 2.6
 *
 * Contributed by Unispeed A/S (http://www.unispeed.com)
 * Author: Casper Wilstup (cwi@unispeed.dk)
 *
 * License: Python Software Foundation License
 *
 */

#include "Python.h"
#include <alsa/asoundlib.h>
#include <stdio.h>


typedef struct {
  PyObject_HEAD;
  int pcmtype;
  int pcmmode;
  char *cardname;
  
  snd_pcm_t *handle;

  // Configurable parameters
  int channels;
  int rate;
  int format;
  snd_pcm_uframes_t periodsize;
  int framesize;

} alsapcm_t;

typedef struct {
  PyObject_HEAD;

  /* Mixer identification */
  char *cardname;
  char *controlname;
  int controlid;

  /* Capabilities */
  unsigned int volume_cap;
  unsigned int switch_cap;
  unsigned int pchannels;
  unsigned int cchannels;

  snd_mixer_t *handle;

} alsamixer_t;

static PyObject *ALSAAudioError;


/******************************************/
/* PCM object wrapper                   */
/******************************************/

static PyTypeObject ALSAPCMType;

static int alsapcm_setup(alsapcm_t *self) {
  int res,dir;
  unsigned int val;
  snd_pcm_hw_params_t *hwparams;
  snd_pcm_uframes_t frames;

  if (self->handle) {
    snd_pcm_close(self->handle);
    self->handle = 0;
  }
  res = snd_pcm_open(&(self->handle),self->cardname,self->pcmtype,self->pcmmode);
  if (res < 0) return res;

  snd_pcm_hw_params_alloca(&hwparams);
  res = snd_pcm_hw_params_any(self->handle, hwparams);
  if (res < 0) return res;

  snd_pcm_hw_params_alloca(&hwparams);

  /* Fill it in with default values. */
  snd_pcm_hw_params_any(self->handle, hwparams);
  snd_pcm_hw_params_set_access(self->handle, hwparams, SND_PCM_ACCESS_RW_INTERLEAVED);
  snd_pcm_hw_params_set_format(self->handle, hwparams, self->format);
  snd_pcm_hw_params_set_channels(self->handle, hwparams, self->channels);
  dir = 0;
  snd_pcm_hw_params_set_rate(self->handle, hwparams, self->rate, dir);
  snd_pcm_hw_params_set_period_size(self->handle, hwparams, self->periodsize, dir);
  snd_pcm_hw_params_set_periods(self->handle,hwparams,4,0);

  res = snd_pcm_hw_params(self->handle, hwparams);

  self->framesize = self->channels * snd_pcm_hw_params_get_sbits(hwparams)/8;
  return res;
}

static PyObject *
alsapcm_new(PyTypeObject *type, PyObject *args, PyObject *kwds) {
  int res;
  alsapcm_t *self;
  int pcmtype=0;
  int pcmmode=0;
  char *cardname = "default";
  if (!PyArg_ParseTuple(args,"|iis",&pcmtype,&pcmmode,&cardname)) return NULL;
  if (!(self = (alsapcm_t *)PyObject_New(alsapcm_t, &ALSAPCMType))) return NULL;

  if (pcmtype != SND_PCM_STREAM_PLAYBACK && pcmtype != SND_PCM_STREAM_CAPTURE) {
    PyErr_SetString(ALSAAudioError, "PCM type must be PCM_PLAYBACK (0) or PCM_CAPTUPE (1)");
    return NULL;
  }
  if (pcmmode < 0 || pcmmode > SND_PCM_ASYNC) {
    PyErr_SetString(ALSAAudioError, "Invalid PCM mode");
    return NULL;
  }
  self->pcmtype = pcmtype;
  self->pcmmode = pcmmode;
  self->cardname = strdup(cardname);
  
  self->channels = 2;
  self->rate = 44100;
  self->format = SND_PCM_FORMAT_S16_LE;
  self->periodsize = 32;

  self->handle = 0;
  res = alsapcm_setup(self);
  if (res < 0) {
    if (self->handle) {
      snd_pcm_close(self->handle);
      self->handle = 0;
    }
    PyErr_SetString(ALSAAudioError, snd_strerror(res));
    return NULL;    
  }
  return (PyObject *)self;
}

static void alsapcm_dealloc(alsapcm_t *self) {
  if (self->handle) {
    snd_pcm_drain(self->handle);
    snd_pcm_close(self->handle);
  }
  free(self->cardname);
  PyObject_Del(self);
}

static PyObject *
alsapcm_dumpinfo(alsapcm_t *self, PyObject *args) {
  unsigned int val,val2;
  int dir;
  snd_pcm_uframes_t frames;
  snd_pcm_hw_params_t *hwparams;
  snd_pcm_hw_params_alloca(&hwparams);
  snd_pcm_hw_params_current(self->handle,hwparams);


  if (!PyArg_ParseTuple(args,"")) return NULL;

  printf("PCM handle name = '%s'\n", snd_pcm_name(self->handle));
  printf("PCM state = %s\n", snd_pcm_state_name(snd_pcm_state(self->handle)));

  snd_pcm_hw_params_get_access(hwparams, (snd_pcm_access_t *) &val);
  printf("access type = %s\n", snd_pcm_access_name((snd_pcm_access_t)val));

  snd_pcm_hw_params_get_format(hwparams, &val);
  printf("format = '%s' (%s)\n", 
	 snd_pcm_format_name((snd_pcm_format_t)val),
	 snd_pcm_format_description((snd_pcm_format_t)val));

  snd_pcm_hw_params_get_subformat(hwparams, (snd_pcm_subformat_t *)&val);
  printf("subformat = '%s' (%s)\n",
	 snd_pcm_subformat_name((snd_pcm_subformat_t)val),
	 snd_pcm_subformat_description((snd_pcm_subformat_t)val));

  snd_pcm_hw_params_get_channels(hwparams, &val);
  printf("channels = %d\n", val);

  snd_pcm_hw_params_get_rate(hwparams, &val, &dir);
  printf("rate = %d bps\n", val);

  snd_pcm_hw_params_get_period_time(hwparams, &val, &dir);
  printf("period time = %d us\n", val);

  snd_pcm_hw_params_get_period_size(hwparams, &frames, &dir);
  printf("period size = %d frames\n", (int)frames);

  snd_pcm_hw_params_get_buffer_time(hwparams, &val, &dir);
  printf("buffer time = %d us\n", val);

  snd_pcm_hw_params_get_buffer_size(hwparams, (snd_pcm_uframes_t *) &val);
  printf("buffer size = %d frames\n", val);

  snd_pcm_hw_params_get_periods(hwparams, &val, &dir);
  printf("periods per buffer = %d frames\n", val);

  snd_pcm_hw_params_get_rate_numden(hwparams, &val, &val2);
  printf("exact rate = %d/%d bps\n", val, val2);

  val = snd_pcm_hw_params_get_sbits(hwparams);
  printf("significant bits = %d\n", val);

  snd_pcm_hw_params_get_tick_time(hwparams, &val, &dir);
  printf("tick time = %d us\n", val);

  val = snd_pcm_hw_params_is_batch(hwparams);
  printf("is batch = %d\n", val);

  val = snd_pcm_hw_params_is_block_transfer(hwparams);
  printf("is block transfer = %d\n", val);

  val = snd_pcm_hw_params_is_double(hwparams);
  printf("is double = %d\n", val);

  val = snd_pcm_hw_params_is_half_duplex(hwparams);
  printf("is half duplex = %d\n", val);

  val = snd_pcm_hw_params_is_joint_duplex(hwparams);
  printf("is joint duplex = %d\n", val);

  val = snd_pcm_hw_params_can_overrange(hwparams);
  printf("can overrange = %d\n", val);

  val = snd_pcm_hw_params_can_mmap_sample_resolution(hwparams);
  printf("can mmap = %d\n", val);

  val = snd_pcm_hw_params_can_pause(hwparams);
  printf("can pause = %d\n", val);

  val = snd_pcm_hw_params_can_resume(hwparams);
  printf("can resume = %d\n", val);

  val = snd_pcm_hw_params_can_sync_start(hwparams);
  printf("can sync start = %d\n", val);

  Py_INCREF(Py_None);
  return Py_None;
    
}

static PyObject *
alsapcm_pcmtype(alsapcm_t *self, PyObject *args) {
  if (!PyArg_ParseTuple(args,"")) return NULL;
  return PyInt_FromLong(self->pcmtype);
}

static PyObject *
alsapcm_pcmmode(alsapcm_t *self, PyObject *args) {
  if (!PyArg_ParseTuple(args,"")) return NULL;
  return PyInt_FromLong(self->pcmmode);
}

static PyObject *
alsapcm_cardname(alsapcm_t *self, PyObject *args) {
  if (!PyArg_ParseTuple(args,"")) return NULL;
  return PyString_FromString(self->cardname);
}

static PyObject *
alsapcm_setchannels(alsapcm_t *self, PyObject *args) {
  int channels;
  int res;
  if (!PyArg_ParseTuple(args,"i",&channels)) return NULL;
  self->channels = channels;
  res = alsapcm_setup(self);
  if (res < 0) {
    PyErr_SetString(ALSAAudioError, snd_strerror(res));
    return NULL;    
  }
  return PyInt_FromLong(channels);
}

static PyObject *
alsapcm_setrate(alsapcm_t *self, PyObject *args) {
  int rate;
  int res;
  if (!PyArg_ParseTuple(args,"i",&rate)) return NULL;
  self->rate = rate;
  res = alsapcm_setup(self);
  if (res < 0) {
    PyErr_SetString(ALSAAudioError, snd_strerror(res));
    return NULL;    
  }
  return PyInt_FromLong(self->rate);
}

static PyObject *
alsapcm_setformat(alsapcm_t *self, PyObject *args) {
  int format;
  int res;
  if (!PyArg_ParseTuple(args,"i",&format)) return NULL;
  self->format = format;
  res = alsapcm_setup(self);
  if (res < 0) {
    PyErr_SetString(ALSAAudioError, snd_strerror(res));
    return NULL;    
  }
  return PyInt_FromLong(self->format);
}

static PyObject *
alsapcm_setperiodsize(alsapcm_t *self, PyObject *args) {
  int periodsize;
  int res;
  if (!PyArg_ParseTuple(args,"i",&periodsize)) return NULL;
  self->periodsize = periodsize;
  res = alsapcm_setup(self);
  if (res < 0) {
    PyErr_SetString(ALSAAudioError, snd_strerror(res));
    return NULL;    
  }
  return PyInt_FromLong(self->periodsize);
}


static PyObject *
alsapcm_read(alsapcm_t *self, PyObject *args) {
  int res;
  int val,dir;
  char buffer[8000];
  snd_pcm_hw_params_t *hwparams;

  if (self->framesize * self->periodsize > 8000) {
    PyErr_SetString(ALSAAudioError,"Capture data too large. Try decreasing period size");
    return NULL;
  }

  if (!PyArg_ParseTuple(args,"")) return NULL;
  if (self->pcmtype != SND_PCM_STREAM_CAPTURE) {
    PyErr_SetString(ALSAAudioError,"Cannot read from playback PCM");
    return NULL;
  }

  res = snd_pcm_readi(self->handle, buffer, self->periodsize);
  if (res == -EPIPE) {
    /* EPIPE means overrun */
    snd_pcm_prepare(self->handle);
  }
  else if (res == -EAGAIN) {
    res = 0;
  }
  else if (res < 0) {
    PyErr_SetString(ALSAAudioError,snd_strerror(res));
    return NULL;
  } 

  return Py_BuildValue("is#",res,buffer,res*self->framesize);
}

static PyObject *alsapcm_write(alsapcm_t *self, PyObject *args) {
  char *data;
  int datalen;
  int res;
  if (!PyArg_ParseTuple(args,"s#",&data,&datalen)) return NULL;
  if (datalen%self->framesize) {
    PyErr_SetString(ALSAAudioError,"Data size must be a multipla of framesize");
    return NULL;
  }
  res = snd_pcm_writei(self->handle, data, datalen/self->framesize);
  if (res == -EPIPE) {
    /* EPIPE means underrun */
    snd_pcm_prepare(self->handle);
    snd_pcm_writei(self->handle, data, datalen/self->framesize);
    snd_pcm_writei(self->handle, data, datalen/self->framesize);
  }
  else if (res == -EAGAIN) {
    return PyInt_FromLong(0);
  }
  else if (res < 0) {
    PyErr_SetString(ALSAAudioError,snd_strerror(res));
    return NULL;
  }  
  return PyInt_FromLong(datalen);
}


/* ALSA PCM Object Bureaucracy */

static PyMethodDef alsapcm_methods[] = {
  {"pcmtype", (PyCFunction)alsapcm_pcmtype, METH_VARARGS},
  {"pcmmode", (PyCFunction)alsapcm_pcmmode, METH_VARARGS},
  {"cardname", (PyCFunction)alsapcm_cardname, METH_VARARGS},
  {"setchannels", (PyCFunction)alsapcm_setchannels, METH_VARARGS},
  {"setrate", (PyCFunction)alsapcm_setrate, METH_VARARGS},
  {"setformat", (PyCFunction)alsapcm_setformat, METH_VARARGS},
  {"setperiodsize", (PyCFunction)alsapcm_setperiodsize, METH_VARARGS},

  {"dumpinfo", (PyCFunction)alsapcm_dumpinfo, METH_VARARGS},

  {"read", (PyCFunction)alsapcm_read, METH_VARARGS},
  {"write", (PyCFunction)alsapcm_write, METH_VARARGS},

  {NULL, NULL}
};

static PyObject *
alsapcm_getattr(alsapcm_t *self, char *name) {
  return Py_FindMethod(alsapcm_methods, (PyObject *)self, name);
}

static PyTypeObject ALSAPCMType = {
  PyObject_HEAD_INIT(&PyType_Type)
  0,                              /*ob_size*/
  "alsaaudio.pcm",                /*tp_name*/
  sizeof(alsapcm_t),              /*tp_basicsize*/
  0,                              /*tp_itemsize*/
  /* methods */    
  (destructor) alsapcm_dealloc,   /*tp_dealloc*/
  0,                              /*print*/
  (getattrfunc)alsapcm_getattr,   /*tp_getattr*/
  0,                              /*tp_setattr*/
  0,                              /*tp_compare*/ 
  0,                              /*tp_repr*/
  0,                              /*tp_as_number*/
  0,                              /*tp_as_sequence*/
  0,                              /*tp_as_mapping*/
  0,                              /*tp_hash*/
  0,                              /*tp_call*/
  0,                              /*tp_str*/
  0,                              /*tp_getattro*/
  0,                              /*tp_setattro*/
  0,                              /*tp_as_buffer*/
  Py_TPFLAGS_DEFAULT,             /*tp_flags*/
  "ALSA PCM device",              /*tp_doc*/
};


/******************************************/
/* Mixer object wrapper                   */
/******************************************/

static PyTypeObject ALSAMixerType;

#define MIXER_CAP_VOLUME            0x0001
#define MIXER_CAP_VOLUME_JOINED     0x0002
#define MIXER_CAP_PVOLUME           0x0004
#define MIXER_CAP_PVOLUME_JOINED    0x0008
#define MIXER_CAP_CVOLUME           0x0010
#define MIXER_CAP_CVOLUME_JOINED    0x0020

#define MIXER_CAP_SWITCH            0x0001
#define MIXER_CAP_SWITCH_JOINED     0x0002
#define MIXER_CAP_PSWITCH           0x0004
#define MIXER_CAP_PSWITCH_JOINED    0x0008
#define MIXER_CAP_CSWITCH           0x0010
#define MIXER_CAP_CSWITCH_JOINED    0x0020
#define MIXER_CAP_CSWITCH_EXCLUSIVE 0x0040

#define MIXER_CHANNEL_ALL -1

int
alsamixer_gethandle(char *cardname, snd_mixer_t **handle) {
  int err;
  if ((err = snd_mixer_open(handle, 0)) < 0) return err;
  if ((err = snd_mixer_attach(*handle, cardname)) < 0) return err;
  if ((err = snd_mixer_selem_register(*handle, NULL, NULL)) < 0) return err;
  if ((err = snd_mixer_load(*handle)) < 0) return err;

  return 0;
}

static PyObject *
alsamixer_list(PyObject *self, PyObject *args) {
  snd_mixer_t *handle;
  snd_mixer_selem_id_t *sid;
  snd_mixer_elem_t *elem;
  int err;
  char *cardname = "default";
  PyObject *result = PyList_New(0);

  if (!PyArg_ParseTuple(args,"|s",&cardname)) return NULL;
	
  snd_mixer_selem_id_alloca(&sid);
  err = alsamixer_gethandle(cardname,&handle);
  if (err < 0) {
    PyErr_SetString(ALSAAudioError,snd_strerror(err));
    snd_mixer_close(handle);
    return NULL;
  }
  for (elem = snd_mixer_first_elem(handle); elem; elem = snd_mixer_elem_next(elem)) {
    PyObject *mixer;
    snd_mixer_selem_get_id(elem, sid);
    mixer = PyString_FromString(snd_mixer_selem_id_get_name(sid));
    PyList_Append(result,mixer);
    Py_DECREF(mixer);
  }
  snd_mixer_close(handle);

  return result;
}

static snd_mixer_elem_t *
alsamixer_find_elem(snd_mixer_t *handle, char *control, int id) {
  snd_mixer_selem_id_t *sid;

  snd_mixer_selem_id_alloca(&sid);
  snd_mixer_selem_id_set_index(sid, id);
  snd_mixer_selem_id_set_name(sid, control);
  return snd_mixer_find_selem(handle, sid);
}

static PyObject *
alsamixer_new(PyTypeObject *type, PyObject *args, PyObject *kwds) {
  alsamixer_t *self;
  int err;
  char *cardname = "default";
  char *control = "Master";
  int id = 0;
  snd_mixer_elem_t *elem;
  int channel;
  
  if (!PyArg_ParseTuple(args,"|sis",&control,&id,&cardname)) return NULL;
  if (!(self = (alsamixer_t *)PyObject_New(alsamixer_t, &ALSAMixerType))) return NULL;

  err = alsamixer_gethandle(cardname,&self->handle);
  if (err<0) {
    PyErr_SetString(ALSAAudioError,snd_strerror(err));
    return NULL;
  }    
  self->cardname = strdup(cardname);
  self->controlname = strdup(control);
  self->controlid = id;

  elem = alsamixer_find_elem(self->handle,control,id);
  if (!elem) {
    char errtext[128];
    sprintf(errtext,"Unable to find mixer control '%s',%i",self->controlname,self->controlid);
    snd_mixer_close(self->handle);
    PyErr_SetString(ALSAAudioError,errtext);
    return NULL;
  }
  /* Determine mixer capabilities */
  self->volume_cap = self->switch_cap = 0;
  if (snd_mixer_selem_has_common_volume(elem)) {
    self->volume_cap |= MIXER_CAP_VOLUME;
    if (snd_mixer_selem_has_playback_volume_joined(elem)) self->volume_cap |= MIXER_CAP_VOLUME_JOINED;
  }
  else {
    if (snd_mixer_selem_has_playback_volume(elem)) {
      self->volume_cap |= MIXER_CAP_PVOLUME;
      if (snd_mixer_selem_has_playback_volume_joined(elem)) self->volume_cap |= MIXER_CAP_PVOLUME_JOINED;
    }
    if (snd_mixer_selem_has_capture_volume(elem)) {
      self->volume_cap |= MIXER_CAP_CVOLUME;
      if (snd_mixer_selem_has_capture_volume_joined(elem)) self->volume_cap |= MIXER_CAP_CVOLUME_JOINED;
    }
  }

  if (snd_mixer_selem_has_common_switch(elem)) {
    self->switch_cap |= MIXER_CAP_SWITCH;
    if (snd_mixer_selem_has_playback_switch_joined(elem)) self->switch_cap |= MIXER_CAP_SWITCH_JOINED;
  }
  else {
    if (snd_mixer_selem_has_playback_switch(elem)) {
      self->switch_cap |= MIXER_CAP_PSWITCH;
      if (snd_mixer_selem_has_playback_switch_joined(elem)) self->switch_cap |= MIXER_CAP_PSWITCH_JOINED;
    }
    if (snd_mixer_selem_has_capture_switch(elem)) {
      self->switch_cap |= MIXER_CAP_CSWITCH;
      if (snd_mixer_selem_has_capture_switch_joined(elem)) self->switch_cap |= MIXER_CAP_CSWITCH_JOINED;
      if (snd_mixer_selem_has_capture_switch_exclusive(elem)) self->switch_cap |= MIXER_CAP_CSWITCH_EXCLUSIVE;
    }
  }
  self->pchannels = 0;
  if (self->volume_cap | MIXER_CAP_PVOLUME || self->switch_cap | MIXER_CAP_PSWITCH) {
    if (snd_mixer_selem_is_playback_mono(elem)) self->pchannels = 1;
    else {
      for (channel=0; channel <= SND_MIXER_SCHN_LAST; channel++) {
	if (snd_mixer_selem_has_playback_channel(elem, channel)) self->pchannels++;
	else break;
      }
    }
  }
  self->cchannels = 0;
  if (self->volume_cap | MIXER_CAP_CVOLUME || self->switch_cap | MIXER_CAP_CSWITCH) {
    if (snd_mixer_selem_is_capture_mono(elem)) self->cchannels = 1;
    else {
      for (channel=0; channel <= SND_MIXER_SCHN_LAST; channel++) {
	if (snd_mixer_selem_has_capture_channel(elem, channel)) self->cchannels++;
	else break;
      }
    }
  }
  return (PyObject *)self;
}

static void alsamixer_dealloc(alsamixer_t *self) {
  if (self->handle) {
    snd_mixer_close(self->handle);
    free(self->cardname);
    free(self->controlname);
    self->handle = 0;
  }
  PyObject_Del(self);
}

static PyObject *
alsamixer_cardname(alsamixer_t *self, PyObject *args) {
  if (!PyArg_ParseTuple(args,"")) return NULL;
  return PyString_FromString(self->cardname);
}

static PyObject *
alsamixer_mixer(alsamixer_t *self, PyObject *args) {
  if (!PyArg_ParseTuple(args,"")) return NULL;
  return PyString_FromString(self->controlname);
}

static PyObject *
alsamixer_mixerid(alsamixer_t *self, PyObject *args) {
  if (!PyArg_ParseTuple(args,"")) return NULL;
  return PyInt_FromLong(self->controlid);
}

static PyObject *
alsamixer_volumecap(alsamixer_t *self, PyObject *args) {
  PyObject *result;
  if (!PyArg_ParseTuple(args,"")) return NULL;
  result = PyList_New(0);
  if (self->volume_cap&MIXER_CAP_VOLUME) 
    PyList_Append(result,PyString_FromString("Volume"));
  if (self->volume_cap&MIXER_CAP_VOLUME_JOINED) 
    PyList_Append(result,PyString_FromString("Joined Volume"));
  if (self->volume_cap&MIXER_CAP_PVOLUME) 
    PyList_Append(result,PyString_FromString("Playback Volume"));
  if (self->volume_cap&MIXER_CAP_PVOLUME_JOINED) 
    PyList_Append(result,PyString_FromString("Joined Playback Volume"));
  if (self->volume_cap&MIXER_CAP_CVOLUME) 
    PyList_Append(result,PyString_FromString("Capture Volume"));
  if (self->volume_cap&MIXER_CAP_CVOLUME_JOINED) 
    PyList_Append(result,PyString_FromString("Joined Capture Volume"));
   
  return result;
}
static PyObject *
alsamixer_switchcap(alsamixer_t *self, PyObject *args) {
  PyObject *result;
  if (!PyArg_ParseTuple(args,"")) return NULL;
  result = PyList_New(0);
  if (self->volume_cap&MIXER_CAP_SWITCH) 
    PyList_Append(result,PyString_FromString("Mute"));
  if (self->volume_cap&MIXER_CAP_SWITCH_JOINED) 
    PyList_Append(result,PyString_FromString("Joined Mute"));
  if (self->volume_cap&MIXER_CAP_PSWITCH) 
    PyList_Append(result,PyString_FromString("Playback Mute"));
  if (self->volume_cap&MIXER_CAP_PSWITCH_JOINED) 
    PyList_Append(result,PyString_FromString("Joined Playback Mute"));
  if (self->volume_cap&MIXER_CAP_CSWITCH) 
    PyList_Append(result,PyString_FromString("Capture Mute"));
  if (self->volume_cap&MIXER_CAP_CSWITCH_JOINED) 
    PyList_Append(result,PyString_FromString("Joined Capture Mute"));
  if (self->volume_cap&MIXER_CAP_CSWITCH_EXCLUSIVE) 
    PyList_Append(result,PyString_FromString("Capture Exclusive"));
  return result;
}

static PyObject *
alsamixer_getvolume(alsamixer_t *self, PyObject *args) {
  snd_mixer_elem_t *elem;
  int direction;
  int channel;
  long ival;
  char *dirstr = 0;
  PyObject *result;

  if (!PyArg_ParseTuple(args,"|s",&dirstr)) return NULL;

  elem = alsamixer_find_elem(self->handle,self->controlname,self->controlid);

  if (!dirstr) {
    if (self->pchannels) direction = 0;
    else direction = 1;
  }
  else if (strcasecmp(dirstr,"playback")==0) direction = 0;
  else if (strcasecmp(dirstr,"capture")==0) direction = 1;
  else {
    PyErr_SetString(ALSAAudioError,"Invalid direction argument for mixer");
    return NULL;
  }
  result = PyList_New(0);
  for (channel = 0; channel <= SND_MIXER_SCHN_LAST; channel++) {
    if (direction == 0 && snd_mixer_selem_has_playback_channel(elem, channel)) {
      snd_mixer_selem_get_playback_volume(elem, channel, &ival);
      PyList_Append(result,PyInt_FromLong(ival));
    }
    else if (direction == 1 && snd_mixer_selem_has_capture_channel(elem, channel)
	     && snd_mixer_selem_has_capture_volume(elem)) {
      snd_mixer_selem_get_capture_volume(elem, channel, &ival);
      PyList_Append(result,PyInt_FromLong(ival));
    }
  }
  return result;
}

static PyObject *
alsamixer_getmute(alsamixer_t *self, PyObject *args) {
  snd_mixer_elem_t *elem;
  int i;
  int ival;
  PyObject *result;
  if (!PyArg_ParseTuple(args,"")) return NULL;

  elem = alsamixer_find_elem(self->handle,self->controlname,self->controlid);
  if (!snd_mixer_selem_has_playback_switch(elem)) {
    PyErr_SetString(ALSAAudioError,"Mixer has no mute switch");
    return NULL;
  }    
  result = PyList_New(0);
  for (i = 0; i <= SND_MIXER_SCHN_LAST; i++) {
    if (snd_mixer_selem_has_playback_channel(elem, i)) {
      snd_mixer_selem_get_playback_switch(elem, i, &ival);
      PyList_Append(result,PyInt_FromLong(!ival));
    }
  }
  return result;
}

static PyObject *
alsamixer_getrec(alsamixer_t *self, PyObject *args) {
  snd_mixer_elem_t *elem;
  int i;
  int ival;
  PyObject *result;
  if (!PyArg_ParseTuple(args,"")) return NULL;

  elem = alsamixer_find_elem(self->handle,self->controlname,self->controlid);
  if (!snd_mixer_selem_has_capture_switch(elem)) {
    PyErr_SetString(ALSAAudioError,"Mixer has no mute switch");
    return NULL;
  }    
  result = PyList_New(0);
  for (i = 0; i <= SND_MIXER_SCHN_LAST; i++) {
    if (snd_mixer_selem_has_capture_channel(elem, i)) {
      snd_mixer_selem_get_capture_switch(elem, i, &ival);
      PyList_Append(result,PyInt_FromLong(!ival));
    }
  }
  return result;
}

static PyObject *
alsamixer_setvolume(alsamixer_t *self, PyObject *args) {
  snd_mixer_elem_t *elem;
  int direction;
  int i;
  int volume;
  char *dirstr = 0;
  int channel = MIXER_CHANNEL_ALL;
  int done = 0;

  if (!PyArg_ParseTuple(args,"i|is",&volume,&channel,&dirstr)) return NULL;

  elem = alsamixer_find_elem(self->handle,self->controlname,self->controlid);

  if (!dirstr) {
    if (self->pchannels) direction = 0;
    else direction = 1;
  }
  else if (strcasecmp(dirstr,"playback")==0) direction = 0;
  else if (strcasecmp(dirstr,"capture")==0) direction = 1;
  else {
    PyErr_SetString(ALSAAudioError,"Invalid direction argument. Use 'playback' or 'capture'");
    return NULL;
  }
  for (i = 0; i <= SND_MIXER_SCHN_LAST; i++) {
    if (channel == -1 || channel == i) {
      if (direction == 0 && snd_mixer_selem_has_playback_channel(elem, i)) {
	snd_mixer_selem_set_playback_volume(elem, i, volume);
	done++;
      }
      else if (direction == 1 && snd_mixer_selem_has_capture_channel(elem, channel)
	       && snd_mixer_selem_has_capture_volume(elem)) {
	snd_mixer_selem_set_capture_volume(elem, i, volume);
	done++;
      }
    }
  }
  if(!done) {
    PyErr_SetString(ALSAAudioError,"No such channel");
    return NULL;
  }
  Py_INCREF(Py_None);
  return Py_None;
}

static PyObject *
alsamixer_setmute(alsamixer_t *self, PyObject *args) {
  snd_mixer_elem_t *elem;
  int i;
  int mute = 0;
  int done = 0;
  int channel = MIXER_CHANNEL_ALL;
  if (!PyArg_ParseTuple(args,"i|i",&mute,&channel)) return NULL;

  elem = alsamixer_find_elem(self->handle,self->controlname,self->controlid);
  if (!snd_mixer_selem_has_playback_switch(elem)) {
    PyErr_SetString(ALSAAudioError,"Mixer has no mute switch");
    return NULL;
  }    
  for (i = 0; i <= SND_MIXER_SCHN_LAST; i++) {
    if (channel == MIXER_CHANNEL_ALL || channel == i) {
      if (snd_mixer_selem_has_playback_channel(elem, i)) {
	snd_mixer_selem_set_playback_switch(elem, i, !mute);
	done++;
      }
    }
  }
  if (!done) {
    PyErr_SetString(ALSAAudioError,"Invalid channel number");
    return NULL;
  }
  Py_INCREF(Py_None);
  return Py_None;
}

static PyObject *
alsamixer_setrec(alsamixer_t *self, PyObject *args) {
  snd_mixer_elem_t *elem;
  int i;
  int rec = 0;
  int done = 0;
  int channel = MIXER_CHANNEL_ALL;
  if (!PyArg_ParseTuple(args,"i|i",&rec,&channel)) return NULL;

  elem = alsamixer_find_elem(self->handle,self->controlname,self->controlid);
  if (!snd_mixer_selem_has_capture_switch(elem)) {
    PyErr_SetString(ALSAAudioError,"Mixer has no record switch");
    return NULL;
  }    
  for (i = 0; i <= SND_MIXER_SCHN_LAST; i++) {
    if (channel == MIXER_CHANNEL_ALL || channel == i) {
      if (snd_mixer_selem_has_capture_channel(elem, i)) {
	snd_mixer_selem_set_playback_switch(elem, i, rec);
	done++;
      }
    }
  }
  if (!done) {
    PyErr_SetString(ALSAAudioError,"Invalid channel number");
    return NULL;
  }
  Py_INCREF(Py_None);
  return Py_None;
}

static PyMethodDef alsamixer_methods[] = {
  {"cardname", (PyCFunction)alsamixer_cardname, METH_VARARGS},
  {"mixer", (PyCFunction)alsamixer_mixer, METH_VARARGS},
  {"mixerid", (PyCFunction)alsamixer_mixerid, METH_VARARGS},
  {"switchcap", (PyCFunction)alsamixer_switchcap, METH_VARARGS},
  {"volumecap", (PyCFunction)alsamixer_volumecap, METH_VARARGS},
  {"getvolume", (PyCFunction)alsamixer_getvolume, METH_VARARGS},
  {"getmute", (PyCFunction)alsamixer_getmute, METH_VARARGS},
  {"getrec", (PyCFunction)alsamixer_getrec, METH_VARARGS},
  {"setvolume", (PyCFunction)alsamixer_setvolume, METH_VARARGS},
  {"setmute", (PyCFunction)alsamixer_setmute, METH_VARARGS},
  {"setrec", (PyCFunction)alsamixer_setrec, METH_VARARGS},
  {NULL, NULL}
};


static PyObject *
alsamixer_getattr(alsapcm_t *self, char *name) {
  return Py_FindMethod(alsamixer_methods, (PyObject *)self, name);
}

static PyTypeObject ALSAMixerType = {
  PyObject_HEAD_INIT(&PyType_Type)
  0,                              /*ob_size*/
  "alsaaudio.mixer",              /*tp_name*/
  sizeof(alsamixer_t),            /*tp_basicsize*/
  0,                              /*tp_itemsize*/
  /* methods */    
  (destructor) alsamixer_dealloc, /*tp_dealloc*/
  0,                              /*print*/
  (getattrfunc)alsamixer_getattr, /*tp_getattr*/
  0,                              /*tp_setattr*/
  0,                              /*tp_compare*/ 
  0,                              /*tp_repr*/
  0,                              /*tp_as_number*/
  0,                              /*tp_as_sequence*/
  0,                              /*tp_as_mapping*/
  0,                              /*tp_hash*/
  0,                              /*tp_call*/
  0,                              /*tp_str*/
  0,                              /*tp_getattro*/
  0,                              /*tp_setattro*/
  0,                              /*tp_as_buffer*/
  Py_TPFLAGS_DEFAULT,             /*tp_flags*/
  "ALSA Mixer Control",           /*tp_doc*/
};


/******************************************/
/* Module initialization                  */
/******************************************/

static PyMethodDef alsaaudio_methods[] = {
  { "mixers", alsamixer_list, METH_VARARGS },
  { 0, 0 },
};

#define _EXPORT_INT(mod, name, value) \
  if (PyModule_AddIntConstant(mod, name, (long) value) == -1) return;

void initalsaaudio(void) {
  PyObject *m;
  ALSAPCMType.tp_new = alsapcm_new;
  ALSAMixerType.tp_new = alsamixer_new;
  m = Py_InitModule("alsaaudio",alsaaudio_methods);

  ALSAAudioError = PyErr_NewException("alsaaudio.ALSAAudioError", NULL, NULL);
  if (ALSAAudioError) {
    /* Each call to PyModule_AddObject decrefs it; compensate: */

    Py_INCREF(&ALSAPCMType);
    PyModule_AddObject(m,"PCM",(PyObject *)&ALSAPCMType);

    Py_INCREF(&ALSAMixerType);
    PyModule_AddObject(m,"Mixer",(PyObject *)&ALSAMixerType);

    Py_INCREF(ALSAAudioError);
    PyModule_AddObject(m, "ALSAAudioError", ALSAAudioError);
  }


  _EXPORT_INT(m,"PCM_PLAYBACK",SND_PCM_STREAM_PLAYBACK);
  _EXPORT_INT(m,"PCM_CAPTURE",SND_PCM_STREAM_CAPTURE);

  _EXPORT_INT(m,"PCM_NONBLOCK",SND_PCM_NONBLOCK);
  _EXPORT_INT(m,"PCM_ASYNC",SND_PCM_ASYNC);

  /* PCM Formats */
  _EXPORT_INT(m,"PCM_FORMAT_S8",SND_PCM_FORMAT_S8);
  _EXPORT_INT(m,"PCM_FORMAT_U8",SND_PCM_FORMAT_U8);
  _EXPORT_INT(m,"PCM_FORMAT_S16_LE",SND_PCM_FORMAT_S16_LE);
  _EXPORT_INT(m,"PCM_FORMAT_S16_BE",SND_PCM_FORMAT_S16_BE);
  _EXPORT_INT(m,"PCM_FORMAT_U16_LE",SND_PCM_FORMAT_U16_LE);
  _EXPORT_INT(m,"PCM_FORMAT_U16_BE",SND_PCM_FORMAT_U16_BE);
  _EXPORT_INT(m,"PCM_FORMAT_S24_LE",SND_PCM_FORMAT_S24_LE);
  _EXPORT_INT(m,"PCM_FORMAT_S24_BE",SND_PCM_FORMAT_S24_BE);
  _EXPORT_INT(m,"PCM_FORMAT_U24_LE",SND_PCM_FORMAT_U24_LE);
  _EXPORT_INT(m,"PCM_FORMAT_U24_BE",SND_PCM_FORMAT_U24_BE);
  _EXPORT_INT(m,"PCM_FORMAT_S32_LE",SND_PCM_FORMAT_S32_LE);
  _EXPORT_INT(m,"PCM_FORMAT_S32_BE",SND_PCM_FORMAT_S32_BE);
  _EXPORT_INT(m,"PCM_FORMAT_U32_LE",SND_PCM_FORMAT_U32_LE);
  _EXPORT_INT(m,"PCM_FORMAT_U32_BE",SND_PCM_FORMAT_U32_BE);
  _EXPORT_INT(m,"PCM_FORMAT_FLOAT_LE",SND_PCM_FORMAT_FLOAT_LE);
  _EXPORT_INT(m,"PCM_FORMAT_FLOAT_BE",SND_PCM_FORMAT_FLOAT_BE);
  _EXPORT_INT(m,"PCM_FORMAT_FLOAT64_LE",SND_PCM_FORMAT_FLOAT64_LE);
  _EXPORT_INT(m,"PCM_FORMAT_FLOAT64_BE",SND_PCM_FORMAT_FLOAT64_BE);
  _EXPORT_INT(m,"PCM_FORMAT_MU_LAW",SND_PCM_FORMAT_MU_LAW);
  _EXPORT_INT(m,"PCM_FORMAT_A_LAW",SND_PCM_FORMAT_A_LAW);
  _EXPORT_INT(m,"PCM_FORMAT_IMA_ADPCM",SND_PCM_FORMAT_IMA_ADPCM);
  _EXPORT_INT(m,"PCM_FORMAT_MPEG",SND_PCM_FORMAT_MPEG);
  _EXPORT_INT(m,"PCM_FORMAT_GSM",SND_PCM_FORMAT_GSM);

}