Release notes for the Zefiro Acoustics ZA2
------------------------------------------

There are known limitations in the ZA2 driver of OSS which are
listed at the end of this document. For this reason we recommend
using RME Digi32 family or Sonorus STUDI/O instead of ZA2 since
the OSS drivers for these cards are significantly better.


NOTICE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
The ZA2 driver is a separately priced option of OSS. You should
select the ZA2 option when ordering the OSS license. The base
price of OSS doesn't contain driver for ZA2.
NOTICE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Due to nature of ZA2 (and digital I/O cards in general) there
are some features that should be remembered when using the card:

1) Only 16 bit stereo sampling format is supported. This means that
mu-Law and/or mono is not supported. However 8 bit format is
handled by software conversion between 16 and 8 bits.
For the above reasons /dev/audio doesn't work like expected
(8 kHz/mono/mu-Law is impossible).

2) Recording speed is always locked to the frequency reported
by the input source (DAT, CD player, etc). This happens when the device file
is opened with O_RDONLY option. Setting the frequency is possible
only when the device is opened with O_WRONLY or O_RDWR flags. In O_RDWR mode
the sampling rate reported by the digital source is ignored. The application
has freedom to set the sampling rate as it wish. It's possible that it doesn't
match actual rate of data sent by the input source so be carefull.

There are two important exceptions to this rule. The ZA2 driver supports
automatic sample rate conversions when recording. This rate compression will
be activated automaticly in the following two cases (with O_RDONLY):

- The input rate reported by the digital input source is 48000 Hz
and the rate requested by the application is 44100 Hz. In this case
the input will be automaticly converted to 44100 Hz using a digital
resampling filter running on the DSP chip of the card.

- The input rate reported by the digital input source is 44100 Hz
and the rate requested by the application is 40500 Hz. In this case
the input will be automaticly converted to 40500 Hz.

If you want to ensure that no conversions are done the recording application
should check the original sampling rate by calling the following ioctl().

int rate = 0; /* It's important to initialize this to 0 */
ioctl(dev_dsp_fd, SNDCTL_DSP_SPEED, &rate);

After this call the detected input rate will be reported in "rate". This
call must done before the program changes the sampling rate.

System lockups when using ZA2
-----------------------------

When ZA2 is in the external clock mode the DSP chip stops running
when the input signal disappears (for example the cable is disconnected).
With the current version of the ZA2 driver this may cause system lockup
in some cases. To recover from the lockup you just need to reconnect the
digital input signal (the lockup situation clears after a relatively long
timeout even if the signal is not reconnected). AVOID RECORDING IF YOUR
INPUT SOURCE IS NOT CONNECTED TO THE SELECTED INPUT.

Selecting the input source
--------------------------

It's possible to select the digital input source using the mixer program
included in this package in the following way:

mixer +rec dig1 - Selects Toslink
mixer +rec dig2 - Selects Coax
mixer +rec dig3 - Selects XLR

Known problems in the ZA2 driver
--------------------------------

In addition to the possible lockups during recording (above) there are few
known problems with the driver. There are no plans to fix these problems
in future OSS versions.

1) The playback rate is fixed to 48000 Hz.
2) There is no support for setting the control bits (generation, etc.) of
the digital playback.
3) Stereo channels may get swapped in rare cases.
4) The driver doesn't support full duplex.

For more information contact info@4front-tech.com