The short answer
Loop recording means the camera writes video in short files, typically a minute or a few minutes each, and when the card is full it deletes the oldest unlocked file to make room for the new one. The camera never stops for lack of space and the card never needs manual cleaning. The G-sensor is an accelerometer that detects a sharp impact or hard braking and marks the current file, and often the previous one, as locked. Locked files move to a protected folder or get a protected flag that the loop cannot overwrite. Most dash cams also offer a lock button for manual saves. The system works well as long as the card survives and the sensitivity is set sensibly.
How the two features interact
| Situation | What the camera does | What can go wrong |
|---|---|---|
| Normal driving | Writes segments, overwrites the oldest | Worn card produces errors or stops |
| Impact detected | Locks current and previous segment | Too-low sensitivity misses a minor bump |
| Rough road | May lock files on every pothole | Protected folder fills and blocks the loop |
| Manual lock button | Locks the current segment | Users forget, or lock too often |
| Card full of locked files | Should warn or overwrite oldest locked | Poor firmware stops recording silently |
The last row is a classic firmware quality test. A camera that quietly stops recording once the protected area fills is far worse than one that warns the user or reserves space for locked clips. Ask what share of the card the locked folder may take, and what the camera does when it is full.
Segments, folders and gaps
Manufacturers split recordings into segments in steps that commonly run from about one to five minutes, and the card usually holds separate folders for normal files, locked event files and photos. Segment length is a trade: shorter segments lose less if one file corrupts and download faster over WiFi, while longer segments mean fewer file breaks and less churn on the card. Two more details are worth checking on a sample. First, whether there is a gap between the end of one segment and the start of the next; a second or two of missing video between files is common, and designs that keep a rolling buffer close it. Second, how the camera names and time-stamps files, because a claim review often needs the clip before and after the event, found quickly.
Why the card is part of the feature
Loop recording rewrites the same cells again and again, which wears an ordinary card out. A worn card usually fails without warning: files turn corrupt, the camera freezes on formatting, or the loop silently stops. That is the reason high-endurance microSD cards, rated for continuous writing, are recommended for loop recording, and why many resellers bundle one with the camera. Speed class (Class 10, U3, V30) matters for 4K bitrates. See dash cam SD cards and the notes on high-endurance cards and corrupted files.
Formatting is part of card life. Cameras format the card in their own way, and formatting on a computer can leave a card that records but misbehaves later, so the manual should tell users to format in the camera and to reformat periodically. Counterfeit and no-name cards remain a common cause of failures, which is why bundling a specified card removes a whole category of support tickets.
G-sensor sensitivity: the setting everyone gets wrong
Most G-sensors offer three to five sensitivity steps, such as low, medium and high. The best default depends on the vehicle. A stiff commercial van or truck jolts at every pothole, so a high setting locks half the day and fills the protected area. A soft-riding car at low sensitivity may not lock a light parking bump. Good firmware ships with a sensible default for the vehicle class and keeps the setting through a power loss. Fleets often want a specific profile for trucks, and that is firmware customization, not a hardware change. See firmware quality.
The G-sensor also drives parking mode wake-up. A bump while parked wakes the camera and starts a protected recording, which is covered in parking mode explained.
Clock handling and locked files
Clock handling belongs to the same review. Files are ordered by the camera's clock, and a camera that loses time at every power cut produces a card full of clips in the wrong order, which is painful in a claim. Good designs keep time across power loss or take it from GPS when present. Ask how the model behaves after a week parked with power removed, and whether the app or viewer flags a suspicious clock. Locked files should also survive a format request from the menu with a clear warning, and they should open on any computer without special software, because an insurer's handler will not install an unusual player.
What happens when power cuts
An impact can also cut power to the camera: a bent connector, a crash that breaks the cable, or a battery cutoff. A power buffer - a supercapacitor in most good designs - gives the camera the fraction of a second it needs to close the last file properly. Without it, the last file can be corrupt, which is often the one that held the impact. Supercapacitors tolerate heat better than lithium batteries, which is a second reason many sourcing programs prefer them. See supercapacitor vs battery.
Audience fit and specification
- Consumers: want it to work without thought; sensible defaults and an audible lock beep matter most.
- Fleets: need adjustable profiles, a reserved protected area and logs that show lock events. See fleet solutions.
- Insurance programs: need reliable locking and a timestamp that cannot be edited by the user.
Taxi and rideshare programs lean hardest on event locking, because incidents inside and around the vehicle are frequent and drivers will not manage files by hand. Insurance-linked programs want locked events that cannot be edited or deleted from the menu, so the evidence chain holds. Entry-level retail buyers mostly need the loop to work silently for years, which is a card and firmware quality question more than a feature question.
- Test the lock on a sample by shaking or striking the unit at each sensitivity step.
- Fill the protected area on a small card and watch the behavior.
- Pull the power during recording and open the last file.
- Check the clock after a full power loss and after GPS lock.
- Download locked files and confirm they open on a computer without special software.
- Check the segment length options and the card capacity advice.
Describe your vehicle mix in the quote form and the shortlist will list the default profile for each model.