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UDP Sound Sync

UDP Sound Sync is a feature to synchronize (share) the sound input of a 'master' device with one or more 'slave' devices. All devices must be running the same release of SR WLED, and they must be in the same local network. Sound Sync is not available in "upstream" WLED by Aircookie. Sound Sync is also different from direct LEDs control using protocols like E1.31, DMX, DDP or AdaLight.

UDP Sound Sync does not sync the actual animations, but rather transmits summary audio sampling information to several devices that still run their own animations locally. In a nutshell, it means that several devices can share a single microphone.


Before configuring UDP Sound Sync, make sure you have gone into the WiFi Preferences and clicked on 'Disable WiFi sleep' at the bottom of the page. It has caused us innumerable problems in the past.

In order to configure UDP sound sync, the ‘master’ needs to be an ESP32 along with an audio input.

You would then to go the ‘Sync Interfaces’ page and configure the 'Audio Sync' at the bottom of the page. Transmit for the ESP32 and Receive for devices without an audio input (either ESP32's or ESP8266's). Make sure the UDP port is the same on all devices.

This does not sync the actual animations, but rather just the transmission of summary audio sampling information (as best we can).

In order to change the UDP Sync Mode (Disabled/Transmit/Receive), you need to power-cycle the ESP32/ESP8266.


When an ESP32 is configured for audio transmission, it will connect to a UDP Multicast address, and begin sending a single UDP Multicast packet containing the data used to generate sound-reactive animations out to any other devices that are configured to receive on the same network. The following information is transmitted:

V1 format, used in SR WLED up to 0.13.x

#define UDP_SYNC_HEADER "00001"
struct audioSyncPacket {
  char header[6] = UDP_SYNC_HEADER;
  uint8_t myVals[32];     //  32 Bytes
  int sampleAgc;          //  04 Bytes
  int sampleRaw;          //  04 Bytes
  float sampleAvg;        //  04 Bytes
  bool samplePeak;        //  01 Bytes
  uint8_t fftResult[16];  //  16 Bytes - FFT results, one byte per GEQ channel
  double FFT_Magnitude;   //  08 Bytes
  double FFT_MajorPeak;   //  08 Bytes

UDP_SYNC_HEADER is a versioning number that's defined in audio_reactive.h

V2 Format - WLED version >= 0.14.0 (including MoonModules fork)

#define UDP_SYNC_HEADER_V2 "00002"
// new "V2" AC 0.14.0 audiosync struct - 40 Bytes
struct audioSyncPacket_v2 {
      char    header[6] = UDP_SYNC_HEADER_V2; // 06 bytes, last byte is '\0' as string terminator.
      float   sampleRaw;      //  04 Bytes  - either "sampleRaw" or "rawSampleAgc" depending on soundAgc setting
      float   sampleSmth;     //  04 Bytes  - either "sampleAvg" or "sampleAgc" depending on soundAgc setting
      uint8_t samplePeak;     //  01 Bytes  - 0 no peak; >=1 peak detected. In future, this will also provide peak Magnitude
      uint8_t reserved1;      //  01 Bytes  - reserved for future extensions like loudness
      uint8_t fftResult[16];  //  16 Bytes  - FFT results, one byte per GEQ channel
      float  FFT_Magnitude;   //  04 Bytes  - magnitude of strongest peak in FFT
      float  FFT_MajorPeak;   //  04 Bytes  - frequency of strongest peak in FFT

The V2 format expects that AGC is performed by the sender, so there is no need to transmit "AGC" and "non-AGC" samples separately. To save bandwidth, the myvals[] array was removed, and all numbers are either float or uint8_t.

SR-WLED 0.13.3 still sends out V1 format, however it is able to receive and decode V2 format, too.

What else ?

You might want to take a look at this library, which allows to send and receive WLED Audio Sync data independent from WLED.

When an ESP32 or ESP8266 is configured to receive audio data from another device, the receiver will disable any onboard microphone sampling and FFT processing, in favor of audio data received from the network. Any time a UDP Multicast packet is received from a transmitter, it will be treated as a discrete microphone sample and stored in memory the same way it would be if it were a local microphone.

  • An ESP8266 will not be able to use any FFT data transmitted from an ESP32, as a result of the differences in hardware and software.

  • The UDP  Multicast  IP is, and the default UDP port is 11988.

  • UDP port can be changed in WLED config pages, for example to have several groups of devices by assigning different UDP ports to each group.

  • UDP multicast is generally not very reliable with typical "consumer grade hardware". Some users found that creating a "port forwarding rule" on their local Wifi router helps. For example, you could create a "dynamic port forwarding rule" for UDP port 11988.

UDP Sound sync brought to you by @spedione on Discord.