Hi David,
The most likely reason for IDeckLinkInput::EnableVideoInput returning E_FAIL, is that the input resource is already tied up, either:
- The input has been enabled by another process, or
- The device is configured for half-duplex profile and the output is enabled. You can check the active profile by running the ActivateProfile SDK sample
It may be worth running StatusMonitor SDK example to check the busy state of the device. This will help determine whether the input or output is enabled. Refer to section 2.7.42 Device Busy State of the SDK Manual for further information.
Regards
Cameron