
           VIA VT8233 SouthBridge audio driver for QNX 6.2

     This driver is intended  for  VIA's  southbridge  VT8233  (VT8233C,
VT8233, VT8233A, VT8235), for the AC'97 codec controller built in  these
southbridges in particular. This driver was ported with the use  of  the
ALSA's 0.9.0-rc3  current  branch  sources. The  sources  of VIA  82C686
driver, shipped as examples with the Audio DDK in QNX 6.1, were used  as
information base.
     The driver for QNX RTP detects VIA's southbridges VT8233 by PCI ID.
Vendor ID for VIA is 0x1106 and Device ID for this southbridge series is
0x3059. The chips a classified by revision number (PCI Revision ID):

     - 0x10 - VT8233 pre-release (not in market).
     - 0x20 - VT8233C.
     - 0x30 - VT8233.
     - 0x40 - VT8233A.
     - 0x50 - VT8235.

     The driver uses Multi-Playback mode, because this mode is supported
by all the given revisions of the chips. There exists  the  multichannel
playback mode (upto 4 simultaneous channels), but the VT8233A lacks  it,
that's  why  Multi-Playback  mode  is  used. Theoretically  the   driver
supports simultaneous 6 channel playback in the interleave  mode  by the
applications which can prepare data for it in the necessary format. 
     AC'97  controller  in  VIA's  VT8233  series  southbridges  doesn't
support VRA (Variable Sampling Rate PCM Audio), that's why this function
fulfilled by the AC'97 codec. Depending on the type  of  the  codec  the
step of sampling rate change  may  vary  by  step  in 1KHz (e.g. ICE1232
AC'97 codec)  upto  hardcoded  rates,  e.g.  8000Hz,  11025Hz,  22050Hz,
44100Hz, 48000Hz .Also depending of the  type  of  the  codec  built  in
motherboard, there can be cases of installation of codec , which doesn't
support  VRA  (these  codecs  work  only  at  48000Hz).  In  such  cases
resampling of audio stream will be done by io-audio  manager  (some  CPU
usage can be felt while  audio  stream  resampling). Processing  of  the
audio stream and checking for needed conditions for audio stream is done
by io-audio  manager. There  are  cases  when  the  AC'97  driver  can't
recognize codec by identifier then instead of its name the its  32bit ID
will be used. ICE1232 (VT1616A) has 0x49434511 identifier.
