Feature for device selection

README.rst

@@ -73,19 +73,20 @@ For validation, run::
 
     $ export BITRATE=48  # explicitly select high MODEM bit rate (assuming good SNR).
     $ amodem -h
-    usage: amodem [-h] {send,recv} ...
+    usage: amodem [-h] {send,recv,lsdev} ...
 
-    Audio OFDM MODEM: 48.0 kb/s (64-QAM x 8 carriers) Fs=32.0 kHz
+    Audio OFDM MODEM v1.15.4: 48.0 kb/s (64-QAM x 8 carriers) Fs=32.0 kHz
 
     positional arguments:
-      {send,recv}
-        send         modulate binary data into audio signal.
-        recv         demodulate audio signal into binary data.
+    {send,recv,lsdev}
+        send             modulate binary data into audio signal.
+        recv             demodulate audio signal into binary data.
+        lsdev            list all devices. (portaudio only)
 
     optional arguments:
-      -h, --help     show this help message and exit
+    -h, --help         show this help message and exit
 
-On, Windows you may download the `portaudio` library from `MinGW <https://packages.msys2.org/base/mingw-w64-portaudio>`_.
+On Windows you may download the `portaudio` library from `MinGW <https://packages.msys2.org/base/mingw-w64-portaudio>`_.
 Then, you should specify the DLL using the following command-line flag::
 
     -l AUDIO_LIBRARY, --audio-library AUDIO_LIBRARY
@@ -136,6 +137,21 @@ and send me the resulting ``audio.raw`` file for debugging::
 
 You can see a screencast of the `calibration process <https://asciinema.org/a/25065?autoplay=1>`_.
 
+Devices
+-------
+To specify an input/output device other than default, set the following environment variables::
+
+    ~/sender $ export OUTAUDIODEVICE=2  # Set output device using device id.
+    ~/sender $ export INAUDIODEVICE=2   # Set input device using device id.
+
+To list input/output devices, use the following command::
+
+    ~/sender $ amodem lsdev
+
+To see details of a specific i/o device, specify the device id using ``-d`` as shown below::
+
+    ~/sender $ amodem lsdev -d 2
+
 Usage
 -----
 

amodem/__main__.py

@@ -12,6 +12,7 @@
 from . import audio
 from . import calib
 from . import main
+from . import lsdev
 from .config import bitrates
 
 
@@ -25,6 +26,9 @@
 bitrate = os.environ.get('BITRATE', 1)
 config = bitrates.get(int(bitrate))
 
+input_device = os.environ.get('INAUDIODEVICE')
+output_device = os.environ.get('OUTAUDIODEVICE')
+
 
 class Compressor:
     def __init__(self, stream):
@@ -71,10 +75,10 @@ def opener(fname):
         if fname is None:
             assert audio_interface is not None
             if 'r' in mode:
-                s = audio_interface.recorder()
+                s = audio_interface.recorder(int(input_device))
                 return async_reader.AsyncReader(stream=s, bufsize=s.bufsize)
             if 'w' in mode:
-                return audio_interface.player()
+                return audio_interface.player(int(output_device))
 
         if fname == '-':
             if 'r' in mode:
@@ -177,6 +181,24 @@ def create_parser(description, interface_factory):
         g.add_argument('-v', '--verbose', default=0, action='count')
         g.add_argument('-q', '--quiet', default=False, action='store_true')
 
+    device_lister = subparsers.add_parser(
+        'lsdev', help='list all devices. (portaudio only)')
+    device_lister.add_argument(
+        '-d', '--device', help='get details of a single device')
+    device_lister.add_argument(
+        '-l', '--audio-library', default='libportaudio.so',
+        help='File name of PortAudio shared library.')
+    device_lister.set_defaults(
+        input_type=FileType('rb'),
+        output_type=FileType('wb'),
+        input=None,
+        output=None,
+        verbose=0,
+        quiet=False,
+        calibrate=False,
+        command='lsdev'
+    )
+
     if argcomplete:
         argcomplete.autocomplete(p)
 
@@ -251,7 +273,12 @@ def interface_factory():
         args.src = args.input_type(args.input)
         args.dst = args.output_type(args.output)
         try:
-            if args.calibrate is False:
+            if args.command == 'lsdev':
+                if args.device:
+                    lsdev.getParticularDevice(interface, int(args.device))
+                else:
+                    lsdev.getDevices(interface)
+            elif args.calibrate is False:
                 args.main(config=config, args=args)
             else:
                 args.calib(config=config, args=args)

amodem/audio.py

@@ -46,11 +46,15 @@ def __exit__(self, *args):
             s.close()
         self.call('Terminate')
 
-    def recorder(self):
-        return Stream(self, config=self.config, read=True)
+    def recorder(self, preferred_device=None):
+        return Stream(
+            self, config=self.config, read=True,
+            preferred_device=preferred_device)
 
-    def player(self):
-        return Stream(self, config=self.config, write=True)
+    def player(self, preferred_device=None):
+        return Stream(
+            self, config=self.config, write=True,
+            preferred_device=preferred_device)
 
 
 class Stream:
@@ -66,7 +70,9 @@ class Parameters(ctypes.Structure):
             ('hostApiSpecificStreamInfo', ctypes.POINTER(None))
         ]
 
-    def __init__(self, interface, config, read=False, write=False):
+    def __init__(
+            self, interface, config,
+            read=False, write=False, preferred_device=None):
         self.interface = interface
         self.stream = ctypes.POINTER(ctypes.c_void_p)()
         self.user_data = ctypes.c_void_p(None)
@@ -80,11 +86,14 @@ def __init__(self, interface, config, read=False, write=False):
         write = bool(write)
         assert read != write  # don't support full duplex
 
-        direction = 'Input' if read else 'Output'
-        api_name = f'GetDefault{direction}Device'
-        index = interface.call(api_name, restype=ctypes.c_int)
+        # use default device if preferred_device is undefined
+        if preferred_device is None:
+            direction = 'Input' if read else 'Output'
+            api_name = f'GetDefault{direction}Device'
+            preferred_device = interface.call(api_name, restype=ctypes.c_int)
+
         self.params = Stream.Parameters(
-            device=index,               # choose default device
+            device=preferred_device,
             channelCount=1,             # mono audio
             sampleFormat=0x00000008,    # 16-bit samples (paInt16)
             suggestedLatency=self.latency,

amodem/lsdev.py

@@ -0,0 +1,39 @@
+from ctypes import *
+
+
+class PADeviceInfo(Structure):
+    _fields_ = [
+        ("structVersion", c_int),
+        ("name", c_char_p),
+        ("hostApi", c_int),
+        ("maxInputChannels", c_int),
+        ("maxOutputChannels", c_int),
+        ("defaultLowInputLatency", c_double),
+        ("defaultLowOutputLatency", c_double),
+        ("defaultHighInputLatency", c_double),
+        ("defaultHighOutputLatency", c_double),
+        ("defaultSampleRate", c_double)
+    ]
+
+
+def printDeviceDetails(device):
+    contents = device.contents
+    print(str(contents.name, 'ascii'))
+    print(f"Input Channels: {contents.maxInputChannels}")
+    print(f"Output Channels: {contents.maxOutputChannels}")
+    print(f"Default Sample Rate: {contents.defaultSampleRate}")
+
+
+def getDevices(interface):
+    num_devices = interface.call('GetDeviceCount', restype=c_int)
+    for i in range(num_devices):
+        device_i = interface.call(
+            'GetDeviceInfo', i, restype=POINTER(PADeviceInfo))
+        device_str = str(device_i.contents.name, 'ascii')
+        print(f"Device #{i}: {device_str}")
+
+
+def getParticularDevice(interface, device_id):
+    device = interface.call(
+        'GetDeviceInfo', device_id, restype=POINTER(PADeviceInfo))
+    printDeviceDetails(device)

setup.py

@@ -2,6 +2,7 @@
 from setuptools import setup
 from setuptools.command.test import test as TestCommand
 
+
 class PyTest(TestCommand):
 
     def finalize_options(self):
@@ -13,6 +14,7 @@ def run_tests(self):
         import pytest
         sys.exit(pytest.main(['.']))
 
+
 setup(
     name='amodem',
     version='1.15.4',