Digital Audio Interfacing and Networking 148339.6.1 Electrical and Optical Interface
Two types of interface are specified, unbalanced elec-
trical and optical fiber.
Three levels of timing accuracy are specified and
indicated in the Channel Status. Level I is the high accu-
racy mode, requiring a tolerance of r50 ppm. Level II is
the normal accuracy mode, requiring a tolerance of
±1000 ppm. Level III is the variable pitch mode. An
exact frequency range is under discussion, but may be
±12.5%.
By default, receivers should be capable of locking to
signals of a Level II accuracy. If a receiver has a
narrower locking range, it must be capable of locking to
signals of a Level I accuracy, and must be specified as a
Level I receiver. If a receiver is capable of normal oper-
ation over the Level III range, it should be specified as a
Level III receiver.
Table 39-4. IEC 60958 Edition 2 StandardChannel Status General Format
Byte 0
Bit 0 0 Contents of the channel status block conform
to IEC 60958-3 “consumer use” Standard.
1 Contents of the channel status block at to the
AES3 “professional use” Standard. Ignore the
rest of this table. (See Note 1.)
Bit 1 0 Audio words consist of linear PCM samples.
1 Audio words consist of something other than
linear PCM samples.
Bit 2 0 Software copyrighted. (See note 2.)
1 Software copyright not claimed.
Bits 3–5 Additional format information, depending on the state
of bit 1.
If bit 1 = 0, linear PCM mode:
Bit 3 4 5
State 0 0 0 2 audio channels not using pre-emphasis.
1 0 0 2 audio channels using 50/15μs pre-emphasis.
0 1 0 Reserved (for 2 audio channels using
pre-emphasis).
1 1 0 Reserved (for 2 audio channels using
pre-emphasis).
All other possible states of bits 3–5 are reserved and
are not to be used unless defined by the IEC in the
future.
If bit 1 = 1, other than linear PCM mode:
Bit 3 4 5
State 0 0 0 Default state.
All other possible states of bits 3–5 are reserved and
are not to be used unless defined by the IEC in the
future.Bits 6 – 7 Channel Status Mode.
Bit 6 7
State 0 0 Mode 0, Consumer use.
All other possible states of bits 6–7 are reserved and
are not to be used unless defined by the IEC in the
future.
Note 1. Other than the use of the Channel Status block of informa-
tion, the rest of the data format is identical between the AES3
“professional use” Standard and the IEC 60958-3 “consumer use”
Standard. The electrical format is different, however. For these
reasons it should never be assumed that a “consumer use”
receiver would function correctly with a “professional use” trans-
mitter, or vice-versa.
Note 2. If the copyright status is unknown for this application, the
state of this bit may alternate at a rate between 4 Hz and 10 Hz.
Channel Status Format for Consumer Use Digital Audio
If Byte 0 bit 1, and bits 6–7 are all 0, then the following applies.
Byte 1—Category Code
Contains the category code indicating the type of equipment gen-
erating the signal. Category codes are given in the annexes to the
Standard. Bit 0 contains the LSB and bit 7 the MSB. Used in con-
junction with the copyright bit to control allowable copying of
material.
Byte 2—Source and Channel Number.
Bits 0–3 Source Number
Bit 0 1 2 3
State 0 0 0 0 Don’t care.
1 0 0 0 1.
0 1 0 0 2.
1 1 0 0 3.1 1 1 1 15.
Bits 4–7 Audio Channel Number.
Bit 4 5 6 7
State 0 0 0 0 Don’t care.
1 0 0 0 A (Left channel of stereo).
0 1 0 0 B (Right channel of stereo).
1 1 0 0 C.
1 1 1 1 O.
Byte 3—Sampling Frequency and Clock Accuracy.
Bits 0–3 Sampling Frequency
Bit 0 1 2 3
State 0 0 0 0 44.1 kHz.
0 1 0 0 48 kHz.
1 1 0 0 32 kHz.
All other possible states of bits 0–3 are reserved and
are not to be used unless defined by the IEC in the
future.
Bits 4–5 Clock Accuracy.
Table 39-4. IEC 60958 Edition 2 Standard
(Continued)