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VS1005 VSOS A
UDIO
S
UBSYSTEM
VS1005g
8.5
Noise Killer Audio Drivers
Because of the way stereo information is transmitted on FM radio, stereo reception is
always more suscept to white noise and other artifacts than mono reception. A way to
reduce or remove the noise is to either dampen the stereo effect at the receiver, or to just
turn FM stereo reception off. The FtNoiseKiller package offers an adaptive FM stereo
radio noise killer algorithm that doesn’t destroy the stereo image.
8.5.1
Driver FTINOISE
Features and limitations:
•
Optimized for 32 kHz operation.
•
Requires about 25 MIPS at 32 kHz 16 bits.
•
Can only handle 16-bit audio (if audio is set to 32 bits, the noise killer is disabled).
The noise killer driver FTINOISE.DL3 connects to
stdaudioin
as shown in Figure 10 on
page 28.
The driver may be controlled either through C ioctl() function calls as described in the
README.TXT file for the driver itself, or from the VSOS Shell using the SETNOISE.DL3
command.
Note: To easily test how the algorithm works, you can start the RDS Radio receiver
(v1.05 or higher) after activating the noise killer driver:
S:>ftinoise
S:>rdsradio
Now you can turn the noise killer off by pushing ’0’, and back on by pushing ’5’ (or ’4’ or
’3’ if reception is poor).
8.5.2
Control Program SETNOISE
Usage: SetNoise [-i|-o] [-v|+v] [-nx] [-h]
-i
Set stdaudioin (default)
-o
Set stdaudioout
-nx
Set noise killer level (default: 50 dB, 0 = off)
-v|+v
Verbose on/off
-h
Show this help
S:>setnoise
Rev. 3.57
2019-04-10
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