En bref:

Pré-requis

• Un kernel compilé avec le module snd-aloop
• jackd2
• python 3

Script python

• jack-aloop-daemon
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  #!/usr/bin/env python
  # -*- coding: utf-8 -*-
  
  # Imports (Global)
  from ctypes import *
  from os import system
  from sys import version_info
  from signal import signal, SIGINT, SIGTERM
  from time import sleep
  
  # --------------------------------------------------
  # Test for python 3.x
  if (version_info >= (3,0)):
    PYTHON3 = True
  else:
    PYTHON3 = False
  
  # --------------------------------------------------
  # Global loop check
  global doLoop, doRunNow
  doLoop   = True
  doRunNow = True
  
  # --------------------------------------------------
  # Global JACK variables
  global sample_rate, buffer_size
  sample_rate = 44100
  buffer_size = 1024
  
  # --------------------------------------------------
  # JACK ctypes implementation
  jacklib = cdll.LoadLibrary("libjack.so.0")
  
  class jack_client_t(Structure):
    _fields_ = []
  
  jack_nframes_t = c_uint32
  
  JackBufferSizeCallback = CFUNCTYPE(c_int, jack_nframes_t, c_void_p)
  JackShutdownCallback = CFUNCTYPE(None, c_void_p)
  
  def jack_client_open(client_name, options, status):
    if (PYTHON3): client_name = client_name.encode("ascii")
    jacklib.jack_client_open.argtypes = [c_char_p, c_int, POINTER(c_int)]
    jacklib.jack_client_open.restype = POINTER(jack_client_t)
    return jacklib.jack_client_open(client_name, options, status)
  
  def jack_client_close(client):
    jacklib.jack_client_close.argtypes = [POINTER(jack_client_t)]
    jacklib.jack_client_close.restype = c_int
    return jacklib.jack_client_close(client)
  
  def jack_activate(client):
    jacklib.jack_activate.argtypes = [POINTER(jack_client_t)]
    jacklib.jack_activate.restype = c_int
    return jacklib.jack_activate(client)
  
  def jack_deactivate(client):
    jacklib.jack_deactivate.argtypes = [POINTER(jack_client_t)]
    jacklib.jack_deactivate.restype = c_int
    return jacklib.jack_deactivate(client)
  
  def jack_connect(client, source_port, destination_port):
    if (PYTHON3): source_port = source_port.encode("ascii")
    if (PYTHON3): destination_port = destination_port.encode("ascii")
    jacklib.jack_connect.argtypes = [POINTER(jack_client_t), c_char_p, c_char_p]
    jacklib.jack_connect.restype = c_int
    return jacklib.jack_connect(client, source_port, destination_port)
  
  def jack_get_sample_rate(client):
    jacklib.jack_get_sample_rate.argtypes = [POINTER(jack_client_t)]
    jacklib.jack_get_sample_rate.restype = jack_nframes_t
    return jacklib.jack_get_sample_rate(client)
  
  def jack_get_buffer_size(client):
    jacklib.jack_get_buffer_size.argtypes = [POINTER(jack_client_t)]
    jacklib.jack_get_buffer_size.restype = jack_nframes_t
    return jacklib.jack_get_buffer_size(client)
  
  def jack_on_shutdown(client, shutdown_callback, arg):
    global _shutdown_callback
    _shutdown_callback = JackShutdownCallback(shutdown_callback)
    jacklib.jack_on_shutdown.argtypes = [POINTER(jack_client_t), JackShutdownCallback, c_void_p]
    jacklib.jack_on_shutdown.restype = None
    jacklib.jack_on_shutdown(client, _shutdown_callback, arg)
  
  def jack_set_buffer_size_callback(client, bufsize_callback, arg):
    global _bufsize_callback
    _bufsize_callback = JackBufferSizeCallback(bufsize_callback)
    jacklib.jack_set_buffer_size_callback.argtypes = [POINTER(jack_client_t), JackBufferSizeCallback, c_void_p]
    jacklib.jack_set_buffer_size_callback.restype = c_int
    return jacklib.jack_set_buffer_size_callback(client, _bufsize_callback, arg)
  
  # --------------------------------------------------
  # quit on SIGINT or SIGTERM
  def signal_handler(sig, frame=0):
    global doLoop
    doLoop = False
  
  # --------------------------------------------------
  # listen to jack shutdown
  def shutdown_callback(arg):
    global doLoop
    doLoop = False
  
  # --------------------------------------------------
  # listen to jack buffer size changes
  def buffer_size_callback(new_buffer_size, arg):
    global doRunNow, buffer_size
    buffer_size = new_buffer_size
    doRunNow = True
    return 0
  
  # --------------------------------------------------
  # run alsa_in and alsa_out
  def run_alsa_bridge():
    global sample_rate, buffer_size
    system("killall alsa_in alsa_out pulseaudio")
    system("env JACK_SAMPLE_RATE=%i JACK_PERIOD_SIZE=%i alsa_in -j alsa_in -dcloop -q 1 2>&1 1> /dev/null &" % (sample_rate, buffer_size))
    system("env JACK_SAMPLE_RATE=%i JACK_PERIOD_SIZE=%i alsa_out -j alsa_out -dploop -q 1 2>&1 1> /dev/null &" % (sample_rate, buffer_size))
  
    # Pause it for a bit, and connect to the proper system ports
    sleep(1)
    jack_connect(client, "alsa_in:capture_1", "system:playback_1")
    jack_connect(client, "alsa_in:capture_2", "system:playback_2")
    jack_connect(client, "system:capture_1", "alsa_out:playback_1")
    jack_connect(client, "system:capture_2", "alsa_out:playback_2")
  
  #--------------- main ------------------
  if __name__ == '__main__':
  
    # Init JACK client
    client = jack_client_open("jack-aloop-daemon", 0, None)
  
    if (not client):
      quit()
  
    jack_on_shutdown(client, shutdown_callback, None)
    jack_set_buffer_size_callback(client, buffer_size_callback, None)
    jack_activate(client)
  
    # Quit when requested
    signal(SIGINT, signal_handler)
    signal(SIGTERM, signal_handler)
  
    # Get initial values
    sample_rate = jack_get_sample_rate(client)
    buffer_size = jack_get_buffer_size(client)
  
    # Keep running until told otherwise
    while (doLoop):
      if (doRunNow):
        run_alsa_bridge()
        doRunNow = False
      sleep(1)
  
    # Close JACK client
    jack_deactivate(client)
    jack_client_close(client)

.asoundrc

• .asoundrc
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  # ------------------------------------------------------
  # Custom asoundrc file for use with snd-aloop and JACK
  #
  # use it like this:
  # env JACK_SAMPLE_RATE=44100 JACK_PERIOD_SIZE=1024 alsa_in (...)
  #
  
  # ------------------------------------------------------
  # playback device
  pcm.aloopPlayback {
    type dmix
    ipc_key 1
    ipc_key_add_uid true
    slave {
      pcm "hw:Loopback,0,0"
      format S32_LE
      rate {
        @func igetenv
        vars [ JACK_SAMPLE_RATE ]
        default 44100
      }
      period_size {
        @func igetenv
        vars [ JACK_PERIOD_SIZE ]
        default 1024
      }
      buffer_size 4096
    }
  }
  
  # capture device
  pcm.aloopCapture {
    type dsnoop
    ipc_key 2
    ipc_key_add_uid true
    slave {
      pcm "hw:Loopback,0,1"
      format S32_LE
      rate {
        @func igetenv
        vars [ JACK_SAMPLE_RATE ]
        default 44100
      }
      period_size {
        @func igetenv
        vars [ JACK_PERIOD_SIZE ]
        default 1024
      }
      buffer_size 4096
    }
  }
  
  # duplex device
  pcm.aloopDuplex {
    type asym
    playback.pcm "aloopPlayback"
    capture.pcm "aloopCapture"
  }
  
  # ------------------------------------------------------
  # default device
  pcm.!default {
    type plug
    slave.pcm "aloopDuplex"
  }
  
  # ------------------------------------------------------
  # alsa_in -j alsa_in -dcloop -q 1
  pcm.cloop {
    type dsnoop
    ipc_key 3
    ipc_key_add_uid true
    slave {
      pcm "hw:Loopback,1,0"
      channels 2
      format S32_LE
      rate {
        @func igetenv
        vars [ JACK_SAMPLE_RATE ]
        default 44100
      }
      period_size {
        @func igetenv
        vars [ JACK_PERIOD_SIZE ]
        default 1024
      }
      buffer_size 32768
    }
  }
  
  # ------------------------------------------------------
  # alsa_out -j alsa_out -dploop -q 1
  pcm.ploop {
    type plug
    slave.pcm "hw:Loopback,1,1"
  }

Action !

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Liens et commentaires

• :
  snd_aloop - snd-aloop
  Alternative à PuseAudio ancien nom de page