Try to execute the command several times in succession. My HDMI Capture Card brings only a useful picture after repeated executions.
Tried a lot of times, same result. May be it's because I'm not using hdmi capture card as this thread states, but simple composite video grabber with only mjpeg supported?
How many power supply points do you have on your led stips?
1 But when I tested red/green/blue/white colors all is fine. Can power issue produce not-solid color when white color is ok? I mean all pixels look powered well and I can imagine problem with data signal, but why with power?
Can you please post your config?