Memory management in event recording systems
View Patent ↗A vehicle event recorder is provided that includes a camera for capturing a video as discrete image frames, and that further includes a managed loop memory and a management system for generating a virtual ‘timeline dilation’ effect. To overcome size limits in the buffer memory of the video event recorder, the maximum time extension of a video series is increased by enabling a reduction in temporal resolution in exchange for an increase in the temporal extension. Memory cells are overwritten in an ‘interleaved’ fashion to produce a reduced frame rate for the recording of certain time periods connected to an event moment. In time periods furthest from the event moment, the resulting frame rate is minimized while in time periods closest to the event moment, the resulting frame rate is maximized.
1. A vehicle event recorder comprising:
a camera configured to obtain optical images and to convert the obtained optical images into electronic signals;
a managed loop buffer memory comprising a rewriteable, electronic storage medium of finite size and configured to receive the electronic signals from the camera and to store the electronic signals as discrete video frames;
an event trigger configured to generate a trigger signal; and
an overwrite device electronically coupled to the managed loop buffer memory and to the event trigger,
the overwrite device being arranged to manage data overwrite operations such that the managed loop buffer memory stores video frames in an interleaved fashion and increases a rate of video frame storage beginning at a first predetermined time before the trigger signal and subsequently decreases the rate of video frame storage after a second predetermined time following the trigger signal.
2. The vehicle event recorder of claim 1 , wherein the overwrite device further is arranged to manage data overwrite operations such that the managed loop buffer memory overwrites video frames in an interleaved fashion by performing overwrite operations on alternate frames or frame sets.
3. The vehicle event recorder of claim 1 , wherein the overwrite device further comprises an overwrite pointer arranged to point to a cell to be overwritten in a future overwrite action.
4. The vehicle event recorder of claim 1 , wherein the overwrite device further comprises a timeline definition, which defines an expanded timeline and virtual frame rates and periods for those frame rates.
5. The vehicle event recorder of claim 4 , wherein the timeline definition includes one timeline having first, second, third, and fourth periods and a timeline midpoint between the second and third periods, the first period being immediately before the second period, the third period being immediately after the second period, and the fourth period being immediately after the third period,
the overwrite device being arranged to manage data overwrite operations such that the managed loop buffer memory stores video frames at a lower frame rate during the first and fourth periods than during the second and third periods.
6. The vehicle event recorder of claim 4 , wherein the timeline definition includes an asymmetry, and wherein the frame rate is different for the periods after the trigger signal than the periods before the trigger signal.
7. The vehicle event recorder of claim 1 , further comprising a high capacity long-term memory coupled to the managed loop buffer memory.
8. The vehicle event recorder of claim 7 , wherein the vehicle event recorder is configured to transfer stored video frames from the managed loop buffer memory to said high capacity long-term memory responsive to the trigger signal.
9. The vehicle event recorder of claim 7 , wherein the transfer of data step resets the managed loop memory into an initial state and a new timeline is initiated.
10. The vehicle event recorder of claim 7 , wherein the video frames transferred to the high capacity long-term memory are not overwritten in successive data transfer steps because the high capacity long-term memory includes capacity sufficient for a plurality of events.
11. A method of dilating a timeline of a video series in a vehicle event recorder, the video recorder comprising a managed loop buffered memory, the method comprising:
receiving video frames from a video camera;
receiving a trigger signal; and
storing the video frames in the managed loop buffered memory in an interleaved fashion and increasing a rate of video frame storage beginning at a first predetermined time before the trigger signal and subsequently decreasing the rate of video frame storage after a second predetermined time following the trigger signal.
12. The method of claim 11 , wherein overwriting data in an interleaved fashion comprises skipping successive frames as to effect a reduced frame rate.
13. The method of claim 12 , further comprising moving an overwrite pointer to a cell not a member of a timeline definition.
14. The method of claim 13 , further comprising applying an overwrite operation to the cell associated with the pointer and further moving the overwrite pointer to another cell not part of the timeline definition.
15. A method of using a managed loop memory device of an event recorder system, the method comprising:
receiving at the event recorder system video frames from a video camera;
receiving a trigger signal;
associating each memory cell of a plurality of memory cells at the managed loop memory device with a corresponding single video frame;
associating an overwrite pointer with one of the memory cells; and
providing at the managed loop memory device an overwrite manager, the overwrite manager comprising a timeline definition, the overwrite manager directing the overwrite pointer to be associated with a memory cell that no longer remains a member of the timeline definition, thus subjecting that memory cell to an impending overwrite action,
the overwrite manager further increasing a rate of video frame storage in the plurality of memory cells beginning at a first predetermined time before the trigger signal and subsequently decreasing the rate of video frame storage in the plurality of memory cells after a second predetermined time following the trigger signal.
16. A method of using a managed loop memory device of an event recorder system, the method comprising comprising:
receiving at the event recorder system images from a video camera;
associating each memory cell of a plurality of memory cells at the managed loop memory device with a corresponding single video frame;
associating an overwrite pointer associated with one of the memory cells;
providing at the managed loop memory device a timeline definition, the timeline definition directing the overwrite pointer to be associated with a memory cell that no longer remains a member of the timeline definition, thus subjecting that memory cell to an impending overwrite action, the timeline definition comprising two 12 second periods of 1 frame per second and one 48 second period of 4 frames per second, either of the 12 second periods falling before and after the 48 second period.