ESP32-C5 Wi-Fi 6 Multichannel Audio System

This project implements a wireless multichannel audio link using ESP32-C5 boards. It captures multichannel PCM (I²S) audio and distributes it wirelessly to multiple receivers over 5 GHz Wi-Fi 6 with low latency. The design is inspired by commercial wireless audio systems, but is fully open and DIY.

Project Overview

The system consists of three main components:

1. Ingest Nodes (4× ESP32-C5)

   • Each captures one I²S data line (SD0..SD3) from a multichannel audio source.
   • Operates as I²S slave (using shared BCLK/LRCLK).
   • Sends 1 ms stereo PCM frames via UDP unicast to the Aggregator.

2. Aggregator (1× ESP32-C5 in AP mode)

   • Collects the 4 stereo streams.
   • Re-timestamps and re-sequences frames.
   • Re-broadcasts them over multicast groups (one per stereo pair).

3. Receivers (1+ ESP32-C5 per speaker pair)

   • Each subscribes to the multicast group for its assigned channel (Front L/R, Center/Sub, Surround, Rear).
   • Buffers for jitter and plays out via I²S master to a DAC/amp.

Hardware Setup

• Ingest ESP32-C5 boards (x4):
  • Connect BCLK, LRCLK, and one SDx line (0..3) from your audio source.
  • Each board captures a stereo pair.
• Aggregator ESP32-C5:
  • Runs as Wi-Fi 6 AP (default SSID: WiSA-DIY, channel 36, WPA2).
  • Collects all 4 streams and multicasts to receivers.
• Receiver ESP32-C5 boards (x4 or more):
  • Connect to Aggregator AP.
  • Subscribe to one of the multicast groups (e.g., 239.255.0.11 for Front L/R).
  • I²S Master out to DAC/amp.

Project Structure

common_audio.h    # Shared packet header definition
ingest/           # I²S → UDP unicast (4 builds: SD0..SD3)
aggregator/       # Collects unicast, re-multicasts to 4 groups
receiver/         # Subscribes to one group, plays I²S out

Packet Format

Every 1 ms frame sent over UDP:

[Header 16 bytes +]
  magic:       "AUD0"
  seq_num:     Global sequence number (monotonic)
  sample_ctr:  Total samples since boot (per lane)
  timestamp:   Capture time in µs
  sd_index:    Which SDx lane (0..3)
  sample_bytes:3 (24-bit samples packed in 32-bit slots)
  num_channels:2 (stereo)
[Payload]
  PCM audio frames, stereo interleaved

Build & Flash

• Requires ESP-IDF 5.x (with ESP32-C5 support)
• For each sub-project (ingest/, aggregator/, receiver/):

idf.py set-target esp32c5
idf.py menuconfig   # adjust pins if needed
idf.py build
idf.py flash monitor

• For ingest builds, set SD_INDEX = 0,1,2,3 (in main.c)

How to Deploy

1. Flash 4 Ingest nodes, each on its own SD line (SD0..SD3).
2. Flash 1 Aggregator (becomes AP, SSID WiSA-DIY).
3. Flash 4 Receivers, each pointed to one multicast IP.
4. Connect your DACs/amps to each Receiver’s I²S out.
5. Play audio into your multichannel source → multichannel wireless output!

Notes

• This project is inspired by commercial wireless audio systems (such as WiSA), but is not affiliated with or certified by any such standard.
• Latency and jitter depend on your RF environment and network setup.
• Use for experimentation, DIY audio, or learning.