HH
VS1005 VSOS A
UDIO
S
UBSYSTEM
VS1005g
7.6
S/PDIF Audio Drivers
S/PDIF drivers allow receiving and transmitting audio using a coaxial or optical S/PDIF
bus.
S/PDIF is a one-way channels, so the transmitter always controls the clocking of the
audio. For this reason, and for certain hardware resons, those drivers that need to either
support synchronizing S/PDIF output to input, or to support 44.1 ot 88.2 kHz sample
rates, need to set VS1005’s master clock to either 56.448 or 61.440 MHz.
With the exception of AUOXSPDA.DL3, all drivers connect to
stdaudioin
and/or
stdau-
dioout
if started with parameter “s”. Otherwise, the drivers need to be opened and
accessed manually.
Only one S/PDIF driver may be in use at any given time. It is not possible to run one
input and one output driver, and expect the system to do anything sensible.
Summary of S/PDIF drivers
Name
Sample rates / kHz
Modifies
Exact
Notes
44.1
48
88.2
96
SysClk
1
rates
2
AUOSPDA
X
X
X
3
Automatic output
AUISPD
X
X
X
X
X
Generic input
AUXSPD
X
X
X
X
X
Generic I/O, sync in & out
AUXSPD48
X
X
X
Limited I/O, sync in & out
AUOSP48S
X
X
Output, sync with input
AUOSPD48
X
X
Output at exactly 48 kHz
1
The driver modifies System Clock either 56.448 MHz (for 44.1 or 88.2 kHz operation)
or 61.440 MHz (for 48 or 96 kHz operation). The driver is incompatible with any USB
drivers, or FM receiver software.
2
The driver sample rate is as accurate as the input clock’s 12.288 MHz is.
3
Audio sample rate may be anything up to 96 kHz. It is converted by hardware to the
target sample rate.
7.6.1
Driver AUOSPDA.DL3
AUOSPDA.DL3 captures audio that is being sent to the DAC audio path, and copies it
automatically to the S/PDIF output.
Figure 9 shows the automatic audio path built by the driver. The driver copies the audio
going to the DAC driver, and sends it through a software volume control to the S/PDIF
output. To function, it needs a DAC (e.g. AUODAC.DL3) driver to be installed.
The sample rate is set by default to 96000 Hz, and anything played back is converted to
the target sample rate by the high-quality VS1005 Filterless sample rate downconverter,
then through a software volume control to the SP_LDATA/SP_RDATA registers. As long
Rev. 3.57
2019-04-10
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