I have news.))
Setting CONFIG_LWIP_TCP_WND_DEFAULT = 8192 (no more, no less) solves this.

Minimal working code for testing:
#include "esp_log.h"
#include "nvs_flash.h"
#include "esp_wifi.h"
#include "esp_netif.h"
#include "esp_http_client.h"

#define TAG "SPEEDTEST"
#define HTTP_BUF_SIZE 16384

static void http_read_task(void* vParam)
{
uint32_t received = 0, timestamp1, dt;
char ...

Of course I tried large buffer, and not. On mobile phone, with the same envirinment, playing starts instantly and have no issues. On esp - tens of seconds preliminary buffering doesn't help. Only one task like above, running just for speed measurement, produces solid speeed about 25℅ lower than ...

I kinda listen radio via esp32s3.))
I receive stream like so(simplified for just speed measure):

static void http_read_task(void* vParam)
{
//................
timestamp1 = pdTICKS_TO_MS(xTaskGetTickCount());
received = 0;
while (1) {
len = esp_http_client_read(client, http_buf, HTTP_BUF_SIZE ...