I2S doesn't work properly on STM32F407

I'm trying to launch I2S on STM32F407. Clocks work fine, WS is what I want (8k, 44.1k, etc), CK is 32*WS, MCK is 256*WS. The problem is that data is transfered at a lower speed (twice lower). I.e I send 1000 bytes during 62ms, but it should take 31ms (at 8k sample rate).

Examples of code:

&sharpdefine WAV_BUFFER_SIZE 1000

uint8_t wavReadBuffer[WAV_BUFFER_SIZE];

for(uint16_t i = 0; i < WAV_BUFFER_SIZE; i++){

   wavReadBuffer[i] = 0xff;

}

HAL_I2S_Transmit(&hi2s2, (uint16_t*)wavReadBuffer, WAV_BUFFER_SIZE, 5000);

static void MX_I2S2_Init(void)

{

   hi2s2.Instance = SPI2;

   hi2s2.Init.Mode = I2S_MODE_MASTER_TX;

   hi2s2.Init.Standard = I2S_STANDARD_MSB;

   hi2s2.Init.DataFormat = I2S_DATAFORMAT_16B;

   hi2s2.Init.MCLKOutput = I2S_MCLKOUTPUT_ENABLE;

   hi2s2.Init.AudioFreq = ((uint32_t)8000U);

   hi2s2.Init.CPOL = I2S_CPOL_LOW;

   hi2s2.Init.ClockSource = I2S_CLOCK_PLL;

   hi2s2.Init.FullDuplexMode = I2S_FULLDUPLEXMODE_DISABLE;

   if (HAL_I2S_Init(&hi2s2) != HAL_OK){Error_Handler();}

}