ESP32 Forum

paddlesteamer wrote: ↑

Thu Apr 01, 2021 8:36 pm

Ok, the problem is caused by `uint16_t`. Converting it to `int16_t` solved the problem. Here is the corrected part:

Code: Select all

static int el_process(audio_element_handle_t self, char *buf, int len) {
    int rsize = audio_element_input(self, buf, len);
 
    if (len != rsize || (rsize % 4) != 0) {
        ESP_LOGW(TAG, "unexpected rsize: %d, len: %d", rsize, len);
    }
 
    int16_t lSample, rSample;
    char * lSamplep = (char *) &lSample;
    char * rSamplep = (char *) &rSample;
    for (int i =0; i<rsize; i+=4) {
        rSamplep[0] = buf[i];
        rSamplep[1] = buf[i+1];
 
        lSamplep[0] = buf[i+2];
        lSamplep[1] = buf[i+3];
 
        float a = convertToF32(rSample);
        a *= 0.5;
        rSample = convertToInt16(a);
 
        buf[i] = rSamplep[0];
        buf[i+1] = rSamplep[1];
 
        buf[i+2] = lSamplep[0];
        buf[i+3] = lSamplep[1];
    }
 
    rsize = audio_element_output(self, buf, rsize);
 
    return rsize;
}

Note that int16 to float conversion is not required, I will be using floats in my code that's what it's used here.

#include <driver/i2s.h> 
const int sample_rate = 16000; // 44100 
esp_err_t err;
 
uint16_t buf_len = 32; // 1024
uint8_t *buf = (uint8_t*) calloc(buf_len, sizeof(uint8_t));
int bytes_written = 0;
 
void setup() {
Serial.begin(500000);
delay(100);
Serial.println(" "); Serial.println("Setup I2S ...");
delay(500);
i2s_install();
i2s_setpin();
delay(500); 
}
 
void loop() {
int bytes_read = 0;
while(bytes_read == 0) {
   bytes_read = i2s_read_bytes(I2S_NUM_0, buf, buf_len, portMAX_DELAY);
 } 
 
delay (6); 
 
i2s_write_bytes(I2S_NUM_0, buf, bytes_read, portMAX_DELAY); 
} 
 
void i2s_install() {
const i2s_config_t i2s_config = {
.mode = i2s_mode_t(I2S_MODE_MASTER | I2S_MODE_TX | I2S_MODE_RX),
.sample_rate = sample_rate,
.bits_per_sample = i2s_bits_per_sample_t(16),
.channel_format = I2S_CHANNEL_FMT_ONLY_LEFT,
.communication_format = i2s_comm_format_t(I2S_COMM_FORMAT_I2S | I2S_COMM_FORMAT_I2S_MSB),
.intr_alloc_flags = ESP_INTR_FLAG_LEVEL1, // default interrupt priority
.dma_buf_count = 16, // 32
.dma_buf_len = 64, // 32 * 2
};
err = i2s_driver_install(I2S_NUM_0, &i2s_config, 0, NULL); 
if (err != ESP_OK) { 
 Serial.printf("Failed installing driver_1: %d\n", err);
  while (true);
 } 
Serial.println("I2S driver installed."); 
} 
 
void i2s_setpin() {
const i2s_pin_config_t pin_config = {
.bck_io_num =   26,
.ws_io_num =    25,
.data_out_num = 22,
.data_in_num =  33
  }; 
err = i2s_set_pin(I2S_NUM_0, &pin_config);
if (err != ESP_OK) {
Serial.printf("Failed setting pin_1: %d\n", err);
while (true);
}
Serial.println("I2S pins installed."); Serial.println(" ");
}

paddlesteamer wrote: ↑

Thu Jun 24, 2021 10:13 am

Hello,

I think your approach is not real-time. In the loop function, you first call `i2s_read_bytes` then wait 6 ms, then you send them to i2s output, and then, again you read the next batch. The latter batch you read is 6 ms late. I don't know Arduino-style coding on esp32 but there should be a method where you can register a callback function which will be called every time there are samples ready on i2s input. In your callback function, you should read bytes from i2s input to a buffer, forward them immediately to i2s output, and only after that you should run the encryption process on the buffer. If you really want to wait for AES encryption to complete before you output samples , then you should have an output buffer instead of outputting read bytes immediately, you should output bytes from the beginning of the output buffer and append the read bytes to the output buffer after the encryption process is finished.