Question about i2s_read parameters

[clarkc5]

Hello!

I am building an audio recording system with an ESP32 and external adc (PCM1865)

To start the data reading, I use:

i2s_read(I2S_NUM, user_given_buffer[cnt], user_given_buffer_size, &i2s_bytes_read, 100);


My question is, what is "&i2s_bytes_read" ? And how to use it?

Thank you