dCS 954 User Manual | Manual for Standard Software Version 1.5x |
dCS Ltd | June 2000 |
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AES3 (AES/EBU) Format
Message HandlingThe AES/EBU interface decodes a data structure that conforms to the dCS version of
•preambles, to allow the receiver to sync up
•up to 24 bits of audio data, transmitted lsb first
•V, a validity bit
•U, a user bit, for the "User Message"
•C, a Channel Status bit, for the "System Message"
•P, a parity bit
The message attached to the AES Reference Out depends on the Ref In setting. In Loop or Loop.t modes, it is copied from the Reference In data. When set to Route, the message is copied from the lowest numbered AES input selected. When set to ddC with a PCM input, the message is as follows:
Professional: | On |
Emphasis: | Off |
Off | |
Mode: | Not indicated |
Sample rate: | (Correctly stated) |
Source: | DCS1 |
Destination: | null |
For more information on the way dCS implement the AES3 system message to handle higher sample rates, see the Appendix to this manual. For the formal definition of the AES3 interface, see footnote6, from the AES.
How Far will AES3 Go?The AES/EBU format was designed to go reasonable distances, at 44.1 kS/s and 48 kS/s. Figure 28 and Figure 29 below show it over 16 m and 94 m using average cables. The waveform at 94 m can still be decoded, although it is quite degraded. Cable delay is about 5.6 ns/metre.
At 96 kS/s (twice the data rate the format was designed for) the allowed cable length is less. Figure 30 and Figure 31 below show this over 16 m and 94 m. At 16 m the waveforms are still very good, but at 94 m they are really quite unreliable.
We recommend restricting 96 kS/s cable runs to 20 m or less, and using good cable near this length.
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Manual part no: DOC136954 iss 2B1 | Page 49 | file 135954ma2b1.pdf available from website |
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