NAME

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

SYNOPSIS

       zita-j2a [options]

DESCRIPTION

       This  tool  allows  one  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-ajbridge-
       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)