Hi! At https://github.com/uli/looptest you can find a script to verify video output using a V4L input device. It creates a test pattern in various resolutions using modetest, captures it on a given video input device, and then does a fuzzy compare to verify that the captured frame sorta kinda looks the way it should. The README file explains how to use it and what external tools it relies on. I have run these tests on a Lager board with an HDMI cable connecting HDMI OUT and HDMI IN; I have found these issues with the output signal: - Mode 640x480-60, of all things, does not work. - After switching a couple of times between resolutions that otherwise work, sometimes no valid output is produced anymore. - Two more exotic modes that are in the default mode list (that is used when the input device does not send a valid EDID blob), namely 848x480-60 and 800x600-56, do not produce valid output. When any of these things happen, the output remains invalid until the next reboot, i.e. switching back to a working mode does not help. (There is also an issue with the VIN input, which sometimes fails to use up-to-date DV timings when capturing the first frame after switching modes. This is worked around by capturing the frame twice.) CU Uli
