sample:a2dp_sink built-in DAC noise fix

[jamesztyou]

furthermore, dithering is an option?

void bt_app_a2d_data_cb(const uint8_t *data, uint32_t len)
{
size_t bytes_written;

#ifdef CONFIG_A2DP_SINK_OUTPUT_INTERNAL_DAC

uint16_t * pu16 = (uint16_t *)(data);
uint32_t cnt = len / sizeof(uint16_t);

while (cnt--)
{
*pu16 = 0x8000u ^ *pu16;
pu16++;
}

#endif

i2s_write(0, data, len, &bytes_written, portMAX_DELAY);

if (++m_pkt_cnt % 100 == 0) {
ESP_LOGI(BT_AV_TAG, "Audio packet count %u", m_pkt_cnt);
}
}