Altera Serial Digital Interface (SDI) MegaCore Function - Manual (Page 109)

Chapter 4: SDI Audio IP Cores 4–21
AES Format
February 2013 Altera Corporation Serial Digital Interface (SDI) MegaCore Function
User Guide
AES Format
The SDI cores use the AES standard. The Audio Engineering Society (AES), together
with the European Broadcasting Union (EBU), created a digital audio transmission
standard known as the AES/EBU standard. The AES standard is a digital audio
standard for transporting digital audio signals serially between devices.
Using the AES format requires the entire 64-bit AES frame to be sent serially. As the
AES defines the preambles as biphase mark codes, which cannot be directly decoded
to 4 bits, you must replace the preambles with X = 0000b, Y = 0001b, and Z = 0010b.
This internal AES format serializes the bit-parallel data words by sending the least
significant bits (LSB) first, with the audio sample (up to 24 bits).
Figure 4–4 shows the timing diagram of the internal AES format.
Avalon-ST Audio Interface
To allow the standard components inside SOPC Builder to interconnect, you must
define the Avalon-ST audio interface. The Avalon-ST audio interface must carry audio
to and from physical AES3 interfaces; which means to support the AES3 outputs, the
interface must transport the extra V, U, and C bits. You may create the P bit.
Each audio block consists of 192 frames, and each frame has channels 1 and 2. Each
frame has a combination of the bits shown in
Figure 4–5 .
The Avalon-ST is a packet-based interface, which carries audio information as a
sequence of data packets. The functions define the types of packets as audio data
packets and audio control packets.
Figure 4–4. Internal AES Format Timing Diagram
clock
aud_de
aud_ws
aud_data
Channel
Status
Parity
Y Preamble
LSB = 1
Z/X Preamble
1/0
Word n - Left Channel
32 bits
Z/X Preamble
LSB = 0
Figure 4–5. AES Format
P Preamble 4 bit U C V
AUX data
or
Audio data 4 bit
AES channel pair 1, sub-frame 2 (CH2)
Audio data 20 bit