How to choose a DVR

A video recorder will help to understand the details of an accident or a controversial moment. Buy a video recorder and all the problems on the roads will disappear? Of course not, but two points of strength and three dexterity will be added for sure. Finding out how to buy the coolest and most useful car DVR.

In 1895, two cars collided in Ohio. In those years, there were only two cars in the entire state of Ohio. It is difficult to comprehend what is currently happening on the roads with all the variety and quantity of vehicles. The DVR can be of great help in this road anthill. And that’s what this device consists of.

Optoelectronic path
An optoelectronic path is the basis of any recorder, its most important part. It includes a lens, sensor and processor. The image quality is the sum of the entire set of the path and is determined by the worst element. Proceeding from this, manufacturers are trying to integrate elements of the same level into the device, which, of course, does not exclude unsuccessful engineering solutions.

The lens plays a huge role in obtaining a high-quality picture. With it, the image is projected onto the plane of the matrix. Most often, a lens is a set of special lenses, frames, and apertures. In modern video recorders, from 3 to 7 lenses can be installed. The highest quality and most expensive lens consists of glass lenses, since their resource is noticeably higher than that of polymer ones, and they do not turn yellow or crack over time.

Devices similar in characteristics can be compared by the main lens. The main lens is the first and is installed in the face of the lens. It is designed to collect light rays. Even for budget DVRs, its diameter should not be less than 10 mm. With an average budget, you can already count on a lens up to 20 mm, but most often these are lenses of 14-16 mm. On premium devices, lenses must be at least 20mm in diameter.

pdf dumps

exam dumps

exam questions

pdf questions

practice questions

practice test

There is no direct relationship between the number of lenses and image quality. And even the most expensive lens is somehow inherent in the distortion and deviation of the light flux – aberrations. Aberrations reduce the sharpness and contrast of the image. As a rule, the cheaper the DVR is, the less information about the lens can be found in the description, or inaccurate data may be indicated.

Aperture ratio is also an important parameter. The higher the aperture, the better the video quality and night shooting will be. The f-number indicates the size of the maximum opening of the lens aperture (aperture). The smaller it is, the greater the light transmittance of the lens, which means the better the quality. That is, an f / 1.8 lens will produce better video than an f / 2 lens.

The light focused by the lens hits an analog-digital microcircuit – a matrix consisting of a large number of light-sensitive photodiodes. The matrix converts light into an electrical signal. That goes to the processor, where it is already converted into digital. The larger the physical size of the matrix and the more sensitive photodiodes of the sensor (traditionally also called the physical pixels of the matrix) on it, the better the image detail.

Does good detail make the picture bright and of high quality? Directly no. The image is light. The task of the matrix is ​​to convert light into a digital signal. The more light the matrix can capture, the better the picture will be at the output in the digital signal. Besides the number of pixels, their size is important. It is the size of the pixels that is responsible for light sensitivity. For a high-quality and detailed image, the pixel size must be at least 2 microns.

The number of pixels along the width and height of the matrix determines the size of the image, and their product – the matrix resolution, which is usually measured in megapixels (Mp). The same number of pixels can fit on two matrices of different sizes. This means that the resolution will be the same, but the light sensitivity will be better on a larger matrix. Hence the difference when shooting at night.

The main parameters of the matrix are the physical size (matrix diagonal), the number of pixels and their size. Modern DVRs are available from 0.3 to 8 megapixels.

An important element that is intended for the correct operation of the declared functions. The electrical signals coming from the matrix are processed by the processor, which forms frames of a certain resolution from them.

The most common shooting resolution is 1920×1080 (FullHD). 2K and 4K formats are nevertheless created for other purposes, but DVRs with this resolution are also found on sale. The larger the size of the picture and, accordingly, the finer details can be seen, the more powerful the processor should be. Right? Again, partly.

With an insufficient level of software development, all the advantages of the chosen processor can be leveled by the quality of the code. If the manufacturer has a “no-name”, and its models are like two drops similar to other brands, most likely the “filling” of these devices is crude and in the near future updates will cease to be released.

Some manufacturers specialize in budget models, some – on the introduction of additional functions such as WiFi and radar detectors, others generally go towards action cameras.

Many manufacturers are tricky. Any resolution can be obtained programmatically, even if it is not supported by the matrix. Since the processor is already working with a digital stream, software algorithms simply stretch the picture to the desired size. The image is blurred, the detail deteriorates.

The digital stream that the processor received from the matrix is ​​huge. You will not be able to write it to the memory card. It will fill up quickly. The stream must be compressed using a video codec. The more modern the video codec, the less space the final video file takes up and the less the quality of the recording is lost during compression. To get a video file from the stream, the processor divides it into frames and quickly iterates over it at a certain frequency. The number of frames is regulated in the DVR settings. It is optimal to use 30-60 FPS (Frames per Second).

It is worth noting that many modern processors are able to add service information to the frame, that is, to make a date and time stamp and a speed stamp (if there is a GPS receiver).

Disposable ZM adhesive tape (the kit may contain an additional one)
non-removable (or the main part of the device is removed, the bracket remains hanging on the glass)
difficult to dismantle

Video recorder DEXP A1 Magnet 2 799 *
This is a combined method of fastening and rather refers to the ease of use of an intermediate element – a bracket. The bracket is attached with 3M tape to the surface, and the DVR itself is attached to the bracket using a neodymium magnet. No latches required.

it is required to select a model for the size of the rear-view mirror
the registrar mirror has less reflective power than the original car mirror
Minor element of the device.

Models without a screen have small dimensions and are intended for hidden installation. Management and viewing of the footage is realized through a special application. The application is not always presented simultaneously in the App Store and Google Play.

Recorder memory
All information in DVRs is recorded on an external memory card. In advanced models, in addition, there is also a small built-in internal memory, which is used to duplicate individual fragments. Memory cards come in different formats, but in DVRs, SD (Secure Digital Memory Card) has become the standard.

SD cards come in two form factors – SD and microSD, which differ in size. Those, in turn, are divided into three types:

The SD type will work in all devices that support SD, SDHC, or SDXC, but many DVR models will block cards less than 4GB by default.

SDHC and SDXC are not backward compatible with devices that only accept SD.

SDXC is not backward compatible with devices that only accept SD and SDHC.