Hi I was wondering if it would be possible at all to 'trick' a real or emulated android device into thinking that an image or video file is the camera feed. So that you could open an app like Snapchat that takes content from the camera feed and press record and it would record whatever file you selected. I imagine this might be easier on an emulated android device however I am not sure.
I think Snapchat has the use of the camera integrated into the app, so to do this you would need to replace or hook into the camera driver or firmware. (Or alter the Snapchat app.) Most ways of doing this would require root, I'm not sure about a method to do this offhand.
However, some apps will use an activity from an external camera app. For those, it's totally possible to use another app that registers as a camera app and then does whatever it wants. Here's one app for this: Fake Camera