1ALSA_IO(1)                  General Commands Manual                 ALSA_IO(1)
2
3
4

NAME

6       alsa_in, alsa_out - Jack clients that perform I/O with an alternate au‐
7       dio interface
8

SYNOPSIS

10       alsa_in [options]
11       alsa_out [options]
12
13

DESCRIPTION

15       A JACK client that opens a specified audio interface (different to  the
16       one  used  by the JACK server, if any) and moves audio data between its
17       JACK ports and the interface. alsa_in will provide data from the inter‐
18       face  (potentially  for capture); alsa_out will deliver data to it (for
19       playback).
20
21       The audio interface used by alsa_in/alsa_out does not need to  be  syn‐
22       chronized  with  JACK  backend  (or  the  hardware  it might be using).
23       alsa_in/alsa_out tries to resample the output stream in an  attempt  to
24       compensate for drift between the two clocks.
25
26       As  of jack-0.116.3 this works almost perfectly. It takes some time, to
27       reach absolute resample-rate stability. So give it  some  minutes  (its
28       intended to be running permanently anyways)
29
30

OPTIONS

32       -j  jack_client_name
33              Set Client Name.
34
35       -d  alsa_device
36              Use this Soundcard.
37
38       -v
39              Verbose,  prints  out  resample coefficient and other parameters
40              useful for debugging, every 500ms.  also reports soft xruns.
41
42       -i
43              Instrumentation. This logs the 4  important  parameters  of  the
44              samplerate  control algorithm every 1ms.  You can pipe this into
45              a file, and plot it. Should only be necessary, if  it  does  not
46              work  as expected, and we need to adjust some of the obscure pa‐
47              rameters, to make it work.  Find me on irc.freenode.org #jack in
48              order to set this up correctly.
49
50       -c  channels
51              Set Number of channels.
52
53       -r  sample_rate
54              Set sample_rate. The program resamples as necessary.  So you can
55              connect a 44100 jackd to a soundcard only supporting 48000. (de‐
56              fault is jack sample_rate)
57
58       -p  period_size
59              Set the period size. It is not related to the jackd period_size.
60              Sometimes it affects the  quality  of  the  delay  measurements.
61              Setting this lower than the jackd period_size will only work, if
62              you use a higher number of periods.
63
64       -n  num_period
65              Set number of periods. See note for period_size.
66
67       -q  quality
68              Set the quality of the resampler from 0 to 4.  can  significanly
69              reduce cpu usage.
70
71       -m  max_diff
72              The  value  when  a  soft  xrun occurs. Basically the window, in
73              which the dma pointer may jitter. I don't think its necessary to
74              play with this anymore.
75
76       -t  target_delay
77              The  delay alsa_io should try to approach. Same as for max_diff.
78              It will be setup based on -p and -n which  is  generally  suffi‐
79              cient.
80
81       -s  smooth_array_size
82              This parameter controls the size of the array used for smoothing
83              the delay measurement. Its default is 256.  If you use a  pretty
84              low period size, you can lower the CPU usage a bit by decreasing
85              this parameter.  However most CPU time is spent  in  the  resam‐
86              pling so this will not be much.
87
88       -C  P Control Clamp
89              If  you have a PCI card, then the default value (15) of this pa‐
90              rameter is too high for -p64 -n2... Setting it to 5  should  fix
91              that.  Be aware that setting this parameter too low, lets the hf
92              noise on the delay measurement come through onto the  resampler‐
93              ate, so this might degrade the quality of the output. (but its a
94              threshold value, and it has been chosen, to mask the noise of  a
95              USB  card,  which has an amplitude which is 50 times higher than
96              that of a PCI card, so 5 won't lose you any  quality  on  a  PCI
97              card)
98
99       -S  server_name
100              Server  to  connect to. This option permits to attach to a named
101              jack2 server.
102
103

AUTHOR

105       Torben Hohn
106
107
108
1091.9.17                            April 2021                        ALSA_IO(1)
Impressum