How can I improve the record resolution?

As individual mode, I tried to use QHD, UHD resolution to record, but the resolution of recorded webm file always got poor resolution.
The usage of the server is under low during recording.

OV.initPublisher(‘streamPublish’, {
audioSource: undefined,
videoSource: undefined,
publishAudio: true,
publishVideo: true,
resolution: ‘2560x1440’, // QHD:25601440, UHD:38402160
frameRate: 30,
insertMode: ‘APPEND’,
mirror: false
});

How can I improve the record resolution?