ZITA-REV1(1)						      General Commands Manual						      ZITA-REV1(1)

NAME

       zita-j2a - Use ALSA capture device as a Jack client, with resampling.

SYNOPSIS

       zita-j2a [options]

DESCRIPTION

       This  tool allows to use an ALSA device as a Jack client, to provide additional capture channels. Functionally it is equivalent to alsa_out
       that comes with Jack, but provides much better audio quality.

       The resampling ratio will typically be stable within 1 PPM and change only very smoothly. Delay will be stable as  well	even  under  worse
       case conditions, e.g. the Jack client running near the end of the cycle.

       The  alsa  device  should  be  a  'hw:' one, i.e. direct access to a soundcard and not an ALSA 'plug' device. A well-working Jack system is
       assumed, running in real-time mode.

       The sample rate can be the same as Jack's one, or different.  Minimum delay is obtained by running the alsa device at a lower  period  size
       than  Jack.  This can be done safely as the alsa thread will run at a higher priority, and apart from copying to/from an internal buffer no
       work is done there. There are no restrictions on the product of period_size and number_of_periods as there are for alsa_in and alsa_out.

       zita-j2a will optionally print some information four times per second. The first number is the average loop error  over	the  last  quarter
       second, in samples. It should be reduced to small randowm values close to zero after 15 seconds or so. The second is the dynamic correction
       factor of the nominal resampling ratio. This should converge to a value close to one and not move much.

       You may observe small variations in these numbers when Jack apps are started or stopped. This is  normal.  Anything  else  isn't  -  please
       report.

       When starting, and in case of major trouble, you will see the
	'Starting  synchronisation'  message.  This  can happen if there is a timeout on the Jack server, e.g. a client crashed or terminated in a
       dirty way. Jack1 will skip one or more cycles when new apps are started, or when a large number of port connections  is	done  in  a  short
       time.  his may interrupt the audio signal, but should otherwise not have any ill consequences nor require a restart.

       zita-a2j and zita-j2a will suspend operation while Jack is in
	'freewheeling' mode.

OPTIONS

       -h     Display this text

       -d <device>
	      ALSA playback device [none]

       -r <rate>
	      Sample rate [48000]

       -p <period>
	      Period size [256]

       -n <nfrags>
	      Number of fragments [2]

       -c <nchannels>
	      Number of channels [2]

       -Q <quality>
	      Resampling quality [48]

       -v     Print tracing information [off]

	      Use '-h' to see all options.

SEE ALSO

       A quick guide is available at <http://kokkinizita.linuxaudio.org/linuxaudio/zita-rev1-doc/quickguide.html>

AUTHOR

       zita-ajbridge was written by Fons Adriaensen <fons@linuxaudio.org>.

       This  manual  page  was	written by Robin Gareus <robin@gareus.org> for the Debian project (but may be used by others).	It is based on the
       original README and announce message by Fons Adriaensen.

								    March 2012							      ZITA-REV1(1)