jack1/man/alsa_in.0

.TH ALSA_IO "1" "!DATE!" "!VERSION!"
.SH NAME
\fBalsa_in\fR, \fBalsa_out\fR \- Jack clients that perform I/O with an alternate audio interface
.SH SYNOPSIS
\fBalsa_in\fR [\fIoptions\fR]
.br
\fBalsa_out\fR [\fIoptions\fR]

.SH 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.

.SH OPTIONS
.TP
\fB\-j \fI jack_client_name\fR
.br
Set Client Name.
.TP
\fB\-d \fI alsa_device\fR  
.br
Use this Soundcard.
.TP
\fB\-c \fI channels\fR  
.br
Set Number of channels.
.TP
\fB\-r \fI sample_rate\fR  
.br
Set sample_rate. The program resamples as necessary.
So you can connect a 44k1 jackd to a soundcard only supporting
48k.
.TP
\fB\-m \fI max_diff\fR  
.br
The value when a soft xrun occurs. Basically the window, in which
the dma pointer may jitter. If you see "delay=" in the output of alsa_out
this is too small.
.br
Make sure target_delay is bigger than this.
.TP
\fB\-t \fI target_delay\fR  
.br
The delay alsa_io should try to approach. Tune this to get lower latency.
Must be bigger than max_diff for alsa_out, and should be bigger than max_diff+jackd_period
for alsa_in. 
.TP
\fB\-f \fI catch_factor\fR  
.br
This value sets how fast the samplerate will change.
default is 1000. Try 10000 when you have good relation between
your clocksources. This will make resampling inaudible for example.
.TP
\fB\-p \fI period_size\fR  
.br
Set the period size. It is not related to the jackd period_size.
Sometimes it affects the quality of the delay measurements.
Thats why its configurable.
.TP
\fB\-n \fI num_period\fR  
.br
Set number of periods. See note for period_size.

.SH AUTHOR
Torben Hohn