About FBDEV example error(fbdev_loopback) of DM644x DVSDK.

Hi.
I would like to ask about FBDEV example error of DM644x.
I am trying to run fbdev loopback example which located in
 /dvsdk_2_00_00_22/PSP_02_00_00_140/example/dm644x/fbdev/fbdev_loopback.
Although I did make it and run on DM6446 DVEVM, I could not operate it properly.
I have not changed the default source code of dvsdk.

Does anyone encounter the same problem?
And, could you give me some advise, please?

The error messages are below:

root@:/opt/examples/dm644x/fbdev# ./fbdev_loopback
main : Enter
initializing capture device
Default crop capbility bounds - 0 0 720 576 ; default - 0 0 720 576
setting data format
set_data_format:setting std to auto select
vpbe_setpos(info, &win_pos)
Input video standard is NTSC.
et_data_format:setting data format
set_data_format:requesting width:720 height:576
set_data_format:finally negotiated width:720 height:480
set_data_format:Finally negitaited width:720 height:480
initializing capture buffers
device buffers:3
buffer:0 phy:80a00000 mmap:0x4014b000 length:884736
buffer:1 phy:80f00000 mmap:0x40223000 length:884736
buffer:2 phy:87300000 mmap:0x402fb000 length:884736
initializing display device
Queing buffer:0
Queing buffer:1
Queing buffer:2
vpbe_UE_1 : Enter
/sys/class/davinci_display/ch0/mode was opened successfully
Current mode value is NTSC
Changed mode to NTSC
Failed  FBIO_SETPOS
Failed to init vid1 window
restore_config : Enter
restore_config : Leave
main : Leave
root@: