one screen make a copy of another screen, but only shows the upper left part of another screen

nvidia jetson tx1 connects two screens.

screen 0: minimum 8x8,current 1744x768,maximum 16384x16384
DSI-0 connected primary 1024x768+0+0
1024x768 60.01*+
HDMI-0 connected 720x576+1024+0
720x576 50.00*+

Then,HDMI-0 make a copy of DSI-0 using the command below:
#xrandr --output HDMI-0 --same-as DSI-0 --auto
But, HDMI-0 only shows the upper left part of the DSI-0 .

Thank you very much!

It looks like one screen is running at 1024x768 resolution, while the other screen runs at 720x576 resolution. One screen buffer is copied, and that would be the smaller resolution screen buffer. Scaling is missing. Both screens need to run the same resolution if they are to directly share the same buffer.

Not sure what your options are for scaling…someone may know how to scale between two screens of the same buffer. Note that a screen is a single virtual rectangular buffer with a uniform height regardless of how the buffer maps a monitor to the buffer.

Dear linuxdev,
Thank you very much!