Xiaomi launched the Mix 4 smartphone earlier this week, and it is the company’s first device with an under-display camera. The company calls it CUP (camera under panel) and it was designed to offer a full-screen experience at the expense of selfie quality. That was confirmed by William Lu, Senior VP at Xiaomi, on his Weibo page. Lu recommended people to buy phones with punch holes if they want selfies with the best possible quality from a front-facing camera. He also said that if they left the display area over the camera very visible it would have been better to stick with holes...
Source: https://www.gsmarena.com/xiaomi_exec_mix_4_is_a_phone_for_fullscreen_experience_not_selfies-news-50483.php