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dCS 954 User Manual Manual for Standard Software Version 1.5x
dCS Ltd June 2000
Manual part no: DOC136954 iss 2B1
Page 55
file 135954ma2b1.pdf available from website
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dCS
on + 44 1799 531 999 email to: more@dcsltd.co.uk
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P3D Behaviour
Mute on CRC Error
The P3D format includes error checking. Data is packed into AES3 subframes,
and each subframe is checked for integrity before it is converted to analogue. In
the event of an error being detected in a subframe, the unit mutes the entire
subframe, and passes control over to a more complex control mechanism. This
looks for a long run of error free subframes before it unmutes – v1.36 software
looks for 150 msecs – and displays the message “CRC”. A single data error
can cause quite long mutes.
The reason for the presence of this test is to detect input data of the wrong
format, which will cause full scale white noise, and can potentially damage
equipment. Statistically, the wrong format data can cause a few subframes to
pass the error check occasionally, so muting a single subframe is quite suspect.
Bit Error Rates
The bit error rate (BER) for a dCS 904/dCS 954 running P3D is below 5x10
-14
, (0
errors over 64 hours). The same error rate is likely to hold for all AES3 type
formats.