4200 client software preview, the big picture takes the main stream so it is clear, the small picture takes the sub-stream parameters, compared with the big picture, the small picture has a lower definition. You can click on the upper left corner of the 4200 software, Tools, System Configuration, Image, and uncheck the automatic change of stream type. Back to the main preview interface, select the folder under the monitoring point, right-click, and select all main streams. 

This will force the main stream to be previewed, but it should be noted that all the main stream previews will take up the computer's CPU. If the computer configuration is not very high, it may freeze. So it is recommended that you take a comprehensive consideration, you can take some important monitoring points as the main stream, and some monitoring points as the sub-stream preview.