[LAU] open hw soundcard (was Re: status usb2 for sound)

Giso Grimm gg3137 at vegri.net
Thu Nov 12 03:11:48 EST 2009

Hans Wilmers wrote:
> I guess that jack is too big a burden for the small kind of system we
> are talking about, so the question is, if netjack could be implemented
> standalone - or maybe another suitable mechanism?

It should be possible to implement the netjack protocol also for a
standalone application, but with that I would wait until there are
decisions on the 'final' netjack version. The jack_netsource code is
approximately 2000 lines of C code (including "netjack_packet.c", with
CELT support and transport control).

Since packet loss is probably not acceptable in a 'sound card', it may
be worth to go for a TCP based solution. Also the clock protocol is not
included in netjack.

I see two different scenarios (OSHw = OpenSoundHardware, <---> audio
transport, <===> audio and clock transport, <~~~> audio transport with
drift control/resampling):

a) netjack based solution, one OSHw, no clock protocol, no sync:

alsa_{in,out} <~~~> jackd -dnet <---> OSHw

b) own protocol, multiple OSHw, master clock:

Master Clock
Host sound card
jackd <===> OSHw
      <===> OSHw
      <===> OSHw

c) 'classical' sound card concept:

ALSA driver <---> OSHw
ALSA driver <---> OSHw
ALSA driver <---> OSHw

(ok, that is three). From a recording studio point of view I think that
version (b) is the best. It would require to implement a driver which
itself is a jack client. As a jack client it is platform independent.

- Giso

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