EDIT: I now want this functionality for my iPad also, and not just screen capture of iOS's functioning, but also for the video camera--I want to leave my video camera recording for hours so I can film a hardware malfunction on my TV. As soon as the malfunction happens, I want to hit the save button and be able to save the part of interest.
A friend told me about NVIDIA GeForce's audio recording software that will record up to the last 20 minutes worth of audio & video from your computer as soon as you hit the Record button:
Shadow every game. Share every victory. ShadowPlay records up to the last 20 minutes of your gameplay. Just pulled off an amazing stunt? Hit a hotkey and the game video will be saved to disk. Or, use the manual mode to capture video for as long as you like.
I do not have this hardware, so I have been looking for software with the same functionality.
Does anyone know the name for this kind of functionality? Or is NVIDIA the only company to make this software?
I want it because I'm playing a video game and there is a sound I want to capture, but it only occurs very rarely, so I don't want to have software recording hours of gameplay sound just for the 3 seconds when it finally happens.
(I'm running OS X 10.10)