192 NALOOP(8)
NAME
naloop – run a loop-back test on a DAT-Link interface.
SYNOPSIS
naloop [ –A][–c ][–i input_source ][–l ][–r][–p precision ][–t seconds ][–s srate ][–u unit ]
DESCRIPTION
naloop performs a loop-back test using the NetAudio server with a DAT-Link interface. See netau-
s
diod(8) for details on the server. The server hardware is put into a mode where it generates a ramp
ignal on all of its digital outputs. Meanwhile, data read from the digital inputs is transferred to the
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host computer where it is verified by naloop to be the same ramp signal. By connecting loop-back
ables between the digital inputs and outputs of the DAT-Link, its data transfer capabilities can be
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easily tested.
aloop can also be run while the DAT-Link is connected to a digital audio tape (DAT) machine. When
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the DAT machine is placed in paused-record mode, with the digital input selected as it’s source, th
igital data from the DAT-Link should be passed back to the DAT-Link allowing naloop to function.
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With this setup, a clicking sound should be heard on any headphone or analog outputs from the DAT
achine.
The only subsystem of the DAT-Link not tested by naloop is the remote control capabilities. These
OPTIONS
can be tested using the loop-back option of rctrain(1)
–A Normally, naloop generates channel status bits using the consumer (also known as S/P DIF, or
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f
IEC) standard. By giving the –A option, the channel status will agree with the AES/EBU pro
essional standard which uses 3 pin, XLR connections. The consumer standard is carried on
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the IEC Type II (RCA connectors) and the fiber-optic interconnects, in which case the –A
ption should not be used.
–c When this mode is used, control words including channel status and user bits are also
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transferred to the host where they are also verified. Note that this option doubles the dat
ransfer rate.
–i input_source
Specify the digital input source used by the DAT-Link. The input_source argument may be
i
AES, RCA, fiber or every. This argument may be abbreviated to a single letter. If this option
s not supplied, all three sources are connected together and the result is used as input. If more
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than one source is connected to the DAT-Link, then this option must be used. The every
ption instructs naloop to cycle through all 3 input sources.
–
–l Transfer and verify only left channel data.
r Transfer and verify only right channel data. If neither –r or –l is given, stereo data is
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transferred and verified. Note that the ramp signals generated by naloop on each channel are
lightly different, allowing it to detect channel reversals.
,–q Run in quick test mode. For hosts which cannot verify the input data as fast as it is generated
this option can be used to skip some of the checking.
–p precision
Set number of bits per sample to precision. By default, 16 bit precision is used.
–t seconds
Run each test for seconds seconds. If seconds is zero, then naloop will be run forever, repeat-
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edly using each possible input condition and sampling rate. If not time is given, or if multiple
onditions are tested repeatedly, each test is run for 10 seconds.
–s DAT_sampling_rate
Specify the sampling rate that will be used to generate the digital output data. Legal values
l
t
are 32000, 44100, 48000. If this option is not specified, then naloop will cycle through al
hree sampling rates.
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