What happens when the DMA ring buffer overflows?
If the camera is running (ISO transmission is on) and you request a frame after a snooze, the DMA buffer is probably overflowing and throwing away the latest frames arriving from the camera. The frames you get from the capture functions will always be in chronological order but they may be old and/or irregularly spaced in time. Buffered (READY) frames in the DMA ring buffer can never be overwritten by newer frames.
