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)