The present technology relates to a signal processing device and method, and a program that enable easier and more accurate failure detection. The signal processing device includes: an addition unit that adds test data for failure detection to valid data on which predetermined processing is to be performed, two or more samples processed in parallel in different paths having a same sample value in the test data; and a signal processing unit that performs the predetermined processing on the valid data and the test data that has been added to the valid data by a plurality of the paths. The present technology can be applied to in-car cameras.