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 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)

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 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.

       -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 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.

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

       -q  quality
              Set  the  quality  of  the  resampler  from 0 to 4. This can significanly reduce CPU usage. Higher
              values give better quality and more 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  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.

       -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 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 wont loose you any
              quality on a PCI card)

AUTHOR

       Torben Hohn