QString filename=QFileDialog: : getOpenFileName (this, tr (" Open Video File "), ". ", the tr (" Video Files (*. Avi *. Mp4 *. FLV *. MKV) ")); 

STD: : cout & lt; 
STD: : cout & lt; <"Shuaxin? 2 "& lt; //if the capture. Open (filename. ToLocal8Bit (). The data ())) 
If (the capture. Open (filename. ToStdString ())) 
{

STD: : cout & lt; <"Success" & lt; } 
The else 
STD: : cout & lt; <"Error" & lt; 

Output:
Shuaxin? 1
E:/hs/2020 _01_28_08_38_img_0028. Mp4
Shuaxin? 2
The error
Shuaxin? 3
Can not open the
DllMain DLL_PROCESS_DETACH
Please see great god, I have checked for a week, all online methods are tried, no matter use