Altera SDI Audio IP Cores User Manual
Page 18
audio data size is configurable at compile time and matches the audio data sample size. Including the aux,
the audio data word would be 24 bits.
In Avalon-ST audio, the data is packed as 24 bit symbols, typically with 1 symbol per beat [23:0]. The core
transmits the audio control data as a packet after the audio data to meet the latency requirements.
The packet type identifier defines the packet type. The packet type identifier is the first value of any packet,
when the start of packet signal is high. The audio data packet identifier is 0×A and the audio control data
packet identifier is 0×E.
The table below lists the packet types.
Table 3-5: Avalon-ST Packet Types
Description
Type Identifier
Video data packet
0
User packet types
1–8
Audio data packet
10
Audio control data packet
14
Video control data packet
15
Reserved
9–15
The preamble data, XYZ from AES, describes whether the data is at the start of a block and which channel
the audio refers to. In Avalon-ST audio protocol, you are not required to transport the preamble data because
the information stored in the data is described by the start of packet, end of packet, and channel signals.
The start of packet, end of packet, and channel signals indicate the start of the audio sample data and the
associated audio channel.
For a single audio channel, the channel signal indicates channel 1 for all valid samples. This figure shows an
example of a single audio channel.
Figure 3-7: Single Audio Channel
sop
Audio data
header identifier
Single channel audio data
(Channel = 1)
Audio data control packet
header identifier (LSB 4 bits)
eop
data [23:0]
channel
A
D0
D1
D2
D3
D4
D5
D6
D7 D8
D190 D191
E
V0
V1
V2
V3
V4
V5
V6
V7
U0
C4 C5
C6
C7
1
1
Audio sample data
Audio control data
For multiple channels, the Avalon-ST interface standard allows the packets to interleave across the channels.
By interleaving, the interface allows multiple audio sources to be multiplexed and demultiplexed.
Altera Corporation
SDI Audio IP Functional Description
3-9
Avalon-ST Audio Interface
UG-SDI-AUD
2014.06.30