Varying Offset, can't get no sync to other clients

[LeoSum8]

Hi Phil,
first of all thanks for making the audiotools and the snapclient!

I am trying to get this to work on the "louder ESP32" boards to replace a few raspberry pi based clients around the house.
I got the DAC working via I2C already.

What I can't get to work so far is synchronous playback. It seems that there is a non constant offset between the arduino-snapclient to my other snapclients which seems uncontrollable for me.

Also depending on the settings I played around with so far (enablint/disabling PSRAM, RTOS, Sync-Algorhithms, ...) I allways get a varying degree of noise/stuttering/slow-mo-playback.

The ESP-board has PSRAM available but I am unsure how to make use of it to reduce stuttering. I must confess I don't quite understand the different buffers and timings that can be defined at different places.

Logging is set to warning, so that shouldn't cause the stuttering.
I would also rule out wifi as an issue, as the snapclient implementation form Carlos works at the same spot in my house.

Could you have a look at my sketch and maybe hint me towards where I can improve things?

This is my snapserver.conf:

[http]
enabled = true
doc_root = /share/snapserver/snapweb/

[tcp]

[stream]
stream = librespot:///librespot?name=Spotify&devicename=Multiroom&sampleformat=48000:16:2

codec=opus

# Buffer [ms]
buffer = 400

And this is my sketch:

#include "AudioTools.h"
#include "SnapClient.h"
#include "AudioCodecs/CodecOpus.h"
#include "Wire.h"
#include "api/SnapProcessorRTOS.h" // install https://github.com/pschatzmann/arduino-freertos-addons

#define ARDUINO_LOOP_STACK_SIZE (10 * 1024)

OpusAudioDecoder opus;
I2SStream out;
WiFiClient wifi;
//SnapTimeSyncFixed synch(100, 1.0); // optional configuratioin
SnapTimeSyncDynamic synch(172, 10);
SnapProcessorRTOS rtos(1024*8); // define queue with 8 kbytes
SnapClient client(wifi, out, opus);
//SnapClient client(wifi, out, pcm);

void setup() {
  Serial.begin(115200);

  // login to wifi -> Define values in SnapConfig.h or replace them here
  WiFi.begin(CONFIG_WIFI_SSID, CONFIG_WIFI_PASSWORD);
  Serial.print("Connecting to WiFi ..");
  while (WiFi.status() != WL_CONNECTED) {
    Serial.print('.');
    delay(1000);
  }

  // print ip address
  Serial.println();
  Serial.print("IP Adress: ");
  Serial.println(WiFi.localIP());

  // pull GPIO33 to HIGH, this will turn on the DAC (louder ESP32 specific)
  pinMode(33, OUTPUT);
  digitalWrite(33, HIGH);
  Serial.print("Enabling Amp via Pin 33");
  Serial.println();

  // setup I2C
  Wire.begin(21,27);  
  Serial.print("Starting I2C");
  Serial.println();

  // Setting to HI Z as seen in https://github.com/sonocotta/esp32-tas5805m-dac/blob/main/tas5805m.cpp
  Wire.beginTransmission(0x2D);
  Wire.write(0x03);
  Wire.write(0x02);
  Wire.endTransmission();
  Serial.print("Setting Amp to HI Z");
  Serial.println();

  delay(200);

  // Setting to PLAY as seen in https://github.com/sonocotta/esp32-tas5805m-dac/blob/main/tas5805m.cpp
  Wire.beginTransmission(0x2D);
  Wire.write(0x03);
  Wire.write(0x03);
  Wire.endTransmission();
  Serial.print("Setting Amp to PLAY");
  Serial.println();

  delay(200);
  
  // set volume
  Wire.beginTransmission(0x2D);
  Wire.write(0x4c);
  Wire.write(70);
  Wire.endTransmission();
  Serial.print("Setting Amp to low Volume");
  Serial.println();

  // setup I2S to define custom pins
  auto cfg = out.defaultConfig();
  cfg.pin_bck = 26;
  cfg.pin_ws = 25;
  cfg.pin_data = 22;
  cfg.buffer_size = 512;
  // cfg.buffer_count = 40;
  out.begin(cfg);
  Serial.print("Starting I2S");
  Serial.println();

  // Define CONFIG_SNAPCAST_SERVER_HOST in SnapConfig.h or here
  // client.setServerIP(IPAddress(192,168,178,30));

  // start snap client
  client.setSnapProcessor(rtos);
  client.begin(synch);
  Serial.print("Starting Snapclient");
  Serial.println();
}

void loop() {
  client.doLoop();
}

Thanks a lot!