This is a review for the KDLinks X1 dashcam, which I have used for a couple of months now.

Overall, the X1 is well designed. The picture quality is very good (though not good enough to read license plates at night, but I couldn't find any dashcam that can do that), and the support is very response. The installation is relatively straightforward if the area behind your rear-view mirror is sufficiently smooth so that you can use the suction cup. If the area is textured, you'll have to first glue some intermediate, smooth material on the windshield and attach the suction cup to that.

All these qualities have been discussed at length throughout the internet, so I won't dwell on them much. Instead, I'd like to focus on something that most of the reviews I've read seem to have missed completely: how well the camera is actually capturing and saving footage in critical situations.

The X1 offers two ways to do this: automatically via an acceleration sensor (which is supposed to trigger on collisions), or manually by pressing a "lock" button. Both methods supposedly to ensure that the last n minutes (configurable to 1, 2 or 3 minutes) are not overwritten by later recordings.

Lacking a spare car to crash, I was not able to test the acceleration sensor, so it's probably prudent to always use the manual button as well when you want to save footage (just pressing the button is much easier than checking if the sensor has triggered).

The manual (which KDLinks deliberately does not put online for obscure reasons) claims that pressing the "lock" button guarantees that the last n minutes of video are saved and will not be overwritten by later footage. In my opinion, this must reliably work in any and all situations, and is really the most important function of any dashcam. Saving footage must be extremely simple and reliable, because it is needed most when the user is most likely to pretty agitated and not able to recall any complicated operating instructions.

Unfortunately, the handling of the lock button is more complicated than that. And even worse, none of what I'm describing here is actually mentioned in the manual. In other words, if you rely on your X1 working without having tested it several times, you might be in for an unpleasant surprise when you actuallly need the footage. There are basically three separate issues:

1. Pressing the lock button only protects the footage if the camera screen is active. So if you have turned on the screensaver function (so that there isn't always a moving picture in the corner of your vision), you actually need to press the lock button once, wait until the screen turns on (about a second), and then press it again to lock the footage (pressing it twice in quick succession does not work).
2. The camera saves footage in segments of a fixed length (1,2 or 3 minutes). When there is no more space on the SD card, the oldest non-protected segment is deleted. Unfortunately, this means that when you press the lock button, the camera does not actually lock the last 3 minutes of footage, but it locks the current segment. So if the camera has just started a new segment, pressing the lock button may only capture a few seconds of footage instead of the last three minutes. Putting it different, unless you press the lock button at exactly 2:59, 6:59, 9:59 etc minutes after turning on the camera, you will always end up with less than 3 minutes of protected video.
3. The segment is not actually protected immedatialywhen you press the lock button, but only when the camera starts recording the next segment. So if you press the lock button, but then turn off the camera before the camera has started a new 3 minute interval, the footage you're interested in will be overwritten the next time you start the camera. I think this is especially bad, because it fails in the typical situation where there's an accident, you press the lock button, turn off the car to work things out, and eventually turn on the car again to continue driving.

The support recommends that, instead of using the lock button, one should turn off the camera and remove the SD card. This certainly avoids all the above problems, but it begs the question of why there is an acceleration sensor and manual trigger in the first place.