The AXI4-Stream Audio Interface carries audio samples in AES3 format. The data width over the AXI4-Stream Audio Interface is fixed at 32 bits to carry one sub-frame as shown in the Figure 1. The TID indicates the channel number of the audio data (TID is 0 for channel 1 and TID is 31 for channel 32).
UHD-SDI Audio (Embed) uses TID to identify the group to which incoming audio
need to be embedded. Similarly, UHD-SDI Audio (Extract) uses TID to convey the group from
which audio is extracted. For example, to embed audio onto group 2, send the audio samples
with TID 4, 5, 6, and 7 to the UHD-SDI Audio (Embed). Similarily, the audio extracted from
group 4 is sent out with TID 12, 13, 14, and 15 by UHD-SDI Audio (Extract). The following
table highlights the mapping of AXI4-Stream TID to audio groups and channels in a 32-channel
system.
The following figure highlights the frame structure and the block transition in
multi-channel AXI4-Stream Audio Interface.
| AXI4-Stream TID | Channel Number | SDI Audio Group | Channel Number in Group |
|---|---|---|---|
| 0 | 1 | 1 | 1 |
| 1 | 2 | 1 | 2 |
| 2 | 3 | 1 | 3 |
| 3 | 4 | 1 | 4 |
| 4 | 5 | 2 | 1 |
| 5 | 6 | 2 | 2 |
| 6 | 7 | 2 | 3 |
| 7 | 8 | 2 | 4 |
| 8 | 9 | 3 | 1 |
| 9 | 10 | 3 | 2 |
| 10 | 11 | 3 | 3 |
| 11 | 12 | 3 | 4 |
| 12 | 13 | 4 | 1 |
| 13 | 14 | 4 | 2 |
| 14 | 15 | 4 | 3 |
| 15 | 16 | 4 | 4 |
| 16 | 17 | 5 | 1 |
| 17 | 18 | 5 | 2 |
| 18 | 19 | 5 | 3 |
| 19 | 20 | 5 | 4 |
| 20 | 21 | 6 | 1 |
| 21 | 22 | 6 | 2 |
| 22 | 23 | 6 | 3 |
| 23 | 24 | 6 | 4 |
| 24 | 25 | 7 | 1 |
| 25 | 26 | 7 | 2 |
| 26 | 27 | 7 | 3 |
| 27 | 28 | 7 | 4 |
| 28 | 29 | 8 | 1 |
| 29 | 30 | 8 | 2 |
| 30 | 31 | 8 | 3 |
| 31 | 32 | 8 | 4 |
Figure 1. Multi-Channel AXI4-Stream Audio
Interface