LCM lost package with UDP transfer

hi, LCM friend, I try transfer a Image with LCM , image is 640 640 3 = 1.2 M Bytes / with 30FPS. means 40M/S transfer rate. sender is a high performance PC , receiver is ARM board (CPU 1G*4) first I found it will lost frame , after run 5 seconds. ,it lost a frame every 5 frames.

I change UDP buffer size with below , but not work

net.core.rmem_max=2097152
net.core.rmem_default=2097152
net.core.wmem_default=2097152
net.core.wmem_max=2097152

I compress Image into JPG and decode on ARM , means only 100K pre frame(30HZ) = 3M /S , it reduce a lot of bytes. but not work
I change Image size to 512*512 with JPG compress yes , It work good.
Next I use lcm-logger record into a file , and use lcm-player play it again. It not work again , still lost frame
I use netstat -su and get no UDP package error

So my question is : since ARM board CPU is not full , why LCM lost data ?
since UDP transfer data is low , why LCM lost data ? how can I found when and where it lost frame ?

lcm-proj / lcm

LCM lost package with UDP transfer #501