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

       Torben Hohn

4                                                     2022                                            ALSA_IO(1)

       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 deliver 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  output  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 resample-rate
       stability. So give it some minutes (its intended to be running permanently anyways)

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

-jjack_client_name
              Set Client Name.

       -dalsa_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 algorithm every
              1ms.  You can pipe this into a file, and plot it. Should only be necessary, 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.

       -cchannels
              Set Number of channels.

       -rsample_rate
              Set  sample_rate.  The  program  resamples  as  necessary.   So you can connect a 44100 jackd to a
              soundcard only supporting 48000. (default is jack sample_rate)

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

       -nnum_period
              Set number of periods. See note for period_size.

       -qquality
              Set the quality of the resampler from 0 to 4. can significantly reduce cpu usage.

       -mmax_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.

       -ttarget_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.

       -ssmooth_array_size
              This  parameter  controls  the  size  of  the  array used for smoothing the delay measurement. 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.

       -CPControlClamp
              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 parameter too low, lets the hf noise
              on the delay measurement come through onto the resamplerate, 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 amplitude which is 50 times higher than that of a PCI card, so 5 won't lose  you  any
              quality on a PCI card)

       -Sserver_name
              Server to connect to. This option permits to attach to a named jack2 server.

alsa_in [options]
       alsa_out [options]