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