ALSA_IO(1)                           General Commands Manual                           ALSA_IO(1)

NAME
       alsa_in, alsa_out - Jack clients that perform I/O with an alternate audio interface

SYNOPSIS
       alsa_in [options]
       alsa_out [options]

DESCRIPTION
       A  JACK  client  that  opens a specified audio interface (different to the one used by the
       JACK server, if any) and moves audio data  between  its  JACK  ports  and  the  interface.
       alsa_in  will provide data from the interface (potentially for capture); alsa_out will de‐
       liver data to it (for playback).

       The audio interface used by alsa_in/alsa_out does not need to be  synchronized  with  JACK
       backend  (or the hardware it might be using).  alsa_in/alsa_out tries to resample the out‐
       put stream in an attempt to compensate for drift between the two clocks.

       As of jack-0.116.3 this works almost perfectly. It takes some time, to reach absolute  re‐
       sample-rate  stability.  So  give  it some minutes (its intended to be running permanently
       anyways)

OPTIONS
       -j  jack_client_name
              Set Client Name.

       -d  alsa_device
              Use this Soundcard.

       -v
              Verbose, prints out resample coefficient and other parameters useful for debugging,
              every 500ms.  also reports soft xruns.

       -i
              Instrumentation. This logs the 4 important parameters of the samplerate control al‐
              gorithm every 1ms.  You can pipe this into a file, and plot it. Should only be nec‐
              essary,  if it does not work as expected, and we need to adjust some of the obscure
              parameters, to make it work.  Find me on irc.freenode.org #jack  in  order  to  set
              this up correctly.

       -c  channels
              Set Number of channels.

       -r  sample_rate
              Set  sample_rate.  The  program  resamples as necessary.  So you can connect a 44k1
              jackd to a soundcard only supporting 48k. (default is jack sample_rate)

       -p  period_size
              Set the period size. It is not related to the jackd period_size.  Sometimes it  af‐
              fects the quality of the delay measurements.  Setting this lower than the jackd pe‐
              riod_size will only work, if you use a higher number of periods.

       -n  num_period
              Set number of periods. See note for period_size.

       -q  quality
              Set the quality of the resampler from 0 to 4. can significanly reduce cpu usage.

       -m  max_diff
              The value when a soft xrun occurs. Basically the window, in which the  dma  pointer
              may jitter. I don't think its necessary to play with this anymore.

       -t  target_delay
              The  delay  alsa_io  should try to approach. Same as for max_diff. It will be setup
              based on -p and -n which is generally sufficient.

       -s  smooth_array_size
              This parameter controls the size of the array used for smoothing the delay measure‐
              ment.  Its  default is 256.  If you use a pretty low period size, you can lower the
              CPU usage a bit by decreasing this parameter.  However most CPU time  is  spent  in
              the resampling so this will not be much.

       -C  P Control Clamp
              If  you  have a PCI card, then the default value (15) of this parameter is too high
              for -p64 -n2... Setting it to 5 should fix that.  Be aware that setting this param‐
              eter  too low, lets the hf noise on the delay measurement come through onto the re‐
              samplerate, so this might degrade the quality of the output. (but its  a  threshold
              value, and it has been chosen, to mask the noise of a USB card, which has an ampli‐
              tude which is 50 times higher than that of a PCI card, so  5  won't  lose  you  any
              quality on a PCI card)

AUTHOR
       Torben Hohn

1.9.12                                    February 2018                                ALSA_IO(1)

usage: alsa_out [options]

  -j <jack name> - client name
  -d <alsa_device>
  -c <channels>
  -p <period_size>
  -n <num_period>
  -r <sample_rate>
  -q <sample_rate quality [0..4]
  -m <max_diff>
  -t <target_delay>
  -i  turns on instrumentation
  -v  turns on printouts