Handbook for Sound Engineers

Digital Audio Interfacing and Networking 1485

Each 32 bit channel data is broken down into eight
words of 4 bits each following this scheme:

The 4 bit words are turned into 5 bit words as
follows:

The now 5 bit words are transmitted (left to right) as

follows:

Unlike the coding used for AES3, this coding allows

dc on the link.

AES10 uses a synchronization symbol, 11000 10001

transmitted left to right, which is inserted at least once

per frame to ensure synchronization of the receiver and

transmitter. There are no defined locations for the inser-

tion of this symbol, but it may only be inserted at the 40

bit boundaries between data words. Enough synchroni-

zation symbols should be interleaved between channels

transmitted, and after the last channel has been trans-

mitted, to fill up the total link capacity.

39.7.1 NRZI Encoding

The 5 bit link channel data is encoded using NRZI

polarity free encoding. Each high bit is converted into a

transition from the bit before, while each low bit results

in no transition. In other words a 1 turns into a 1 to 0 or

0 to 1 transition, while a 0 results in a static 1 or 0.

39.7.2 Sample Frequencies and Rates

MADI allows operation with sampling rates in any of

three ranges:

• 32 to 48 kHz, r12.5%, 56 channels.


• 32 to 48 kHz nominal, 64 channels.


• 64 to 96 kHz, r12.5%, 28 channels from the nominal
  frequency.

Higher sampling rates such as 192 kHz require the use

of multiple audio channels per sample.

Data is transmitted across the link at a constant 125

megabits per second irrespective of the number of chan-

nels in use. The data transfer rate is 100 megabits per

second. The difference is due to the 4 data bit to 5 link

bit encoding used.

3 MADI channel block

sync

Channel block start 1 = true

4–27 AES3 audio data bits (bit 27 is MSB)

28 AES3 V Validity bit

29 AES3 U User data bit

30 AES3 C Status data bit

31 AES3 P Parity bit (excludes bits

0–3)

Even

Word Channel Data Bits

00123

14567

2891011

3 12 13 14 15

4 16171819

5 20212223

6 24252627

7 28293031

4 Bit Data 5 Bit Encoded Data

0000 11110

0001 01001

0010 10100

0011 10101

0100 01010

0101 01011

0110 01110

0111 01111

1000 10010

1001 10011

1010 10110

1011 10111

1100 11010

1101 11011

1110 11100

1111 11101

Table 39-5. AES10 MADI (Continued)

Word Channel Link Bits

001234

156789

2 1011121314

3 1516171819

4 2021222324

5 2526272829

6 3031323334

7 3536373839