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ALSA_IO(1)		    General Commands Manual		    ALSA_IO(1)

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

       alsa_in [options]
       alsa_out	[options]

       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	inter-
       face  (potentially  for capture); alsa_out will deliver data to it (for

       The audio interface used	by alsa_in/alsa_out does not need to  be  syn-
       chronized  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)

       -j  jack_client_name
	      Set Client Name.

       -d  alsa_device
	      Use this Soundcard.

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

	      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 pa-
	      rameters,	to make	it work.  Find me on #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.  (de-
	      fault 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  signifi-
	      canly  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	suffi-

       -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	resam-
	      pling so this will not be	much.

       -C  P Control Clamp
	      If you have a PCI	card, then the default value (15) of this  pa-
	      rameter  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 resampler-
	      ate, 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

       Torben Hohn

0-125-0rc1			  August 2020			    ALSA_IO(1)


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