video camera microphone input
How To Choose Web-Camera
Why a web-camera?
Originally web-camera set up to organize the communication and the establishment of teleconferencing via the Internet. It is up to now remains their main purpose. Although if you want you can find many other applications svezhepriobretennoy web-camera. For example, you can shoot video, take photographs, to video surveillance. A modern models can even watch the starry sky.
Web-camera is designed exclusively for multimedia network applications, in which the base rate is not on the quality of the transmitted data (sound and image), and at speed. When choosing web-camera the first thing to pay attention to compatibility with the computer’s operating system, because many models are calculated only on Windows.
The structure of web-camera includes the following components: CCD, lens, optical filter, video capture card, video compression unit, the central processor and built-in web-server, flash memory, network interface, serial ports, alarm inputs / outputs. Some models of cameras are turning devices and can perform a circular video surveillance.
Matrix web-camera
This web-based cameras, however, as any digital optical devices. Differ matrix technology manufacturing. Today, widespread development and application received two technologies – CMOS and CCD. The main difference is that CCD-issue better picture and create less “noise” (interference) than the matrix on the CMOS-sensor. But more expensive.
In addition to the sensor technology, is considered such an important parameter as the resolving power. From the permission matrix depends on the quality of transmitted images. Range of values lies in the range from 0.1 to 2 megapixels (MP), but the most popular resolution VGA, amounting to 0.3 megapixels. (frame size at the same time – 640×480). For the Internet video-conferencing have enough resolution to 320 x 240 pixels. Standard 640 x 480 pixels, which offer all the cameras, ideal for recording small videos that can be sent by e-mail. The most expensive models have a matrix with a resolution of 1 280 x 960 pixels and can do large-scale photographs.
Sensitivity matrix – a parameter that determines the minimum illumination at which the camera can shoot. Measured sensitivity in lux (lux). Especially it is necessary to emphasize that regardless of the cost, almost all cells, even with the CCD-sensors begin to “make noise, make noise, if the matrix gets enough light.
Connecting and installing web-camera
When choosing web-camera, a very close look at the type of connection to the computer. Most models are equipped with a USB-connector, but, as we know, there are two versions of this interface, and they differ greatly in speed. If a web-camera version supports USB 1.1, then the video quality is not the best: 640 x 480 dots (pixels) at 15 frames per second (or the frame rate 15 fps). This will affect the quality of the picture – it will be like a little “slow down”. Therefore, please note that the frequency of the frame was not less than 30 fps. (As a rule, now almost all web-cameras have such a frequency). Increased data stream USB 1.1 can not miss. Therefore we recommend to choose the model that support the USB 2.0.
Connect web-camera to the Internet on cell lines of communication can be via cellular modem. Data transfer rate is usually from 5 to 20 kbps. Cable modems provide Internet access over cable networks. The maximum speed of receiving data up to 40 Mbps, and data transmission rate is about 10 Mbps. Digital Subscriber Line – technology that provides bandwidth for simple copper telephone wires. Data transfer rate may vary depending on the company providing this service.
More expensive models of web-cameras are equipped with wireless interfaces. They are usually divided into two parts – a transmitter (in one case with most cameras) and the receiver, which is also connected to the connector USB. It often is used for signal transmission technology Wi-Fi.
Additional features web-camera
We have already said that the web-camera, in addition to its primary function – broadcasting information over the Internet, have a number of additional. Thus, for advanced users can choose the camera that lets you take pictures, shoot video, edit information, manage the white balance, contrast, brightness, color and gamma correction, and frame rates.
Photography
If you are going to engage in photography, the main parameters in the selection of web-cameras are a great resolution of the matrix and the amount of memory storage. 8 MB of memory allows us not only to do, but also to store images (120 image size 640 * 480, 480 images or 40 seconds of video in the format 320 * 240, or 90 seconds of video in the format 160 * 120).
Videography
When recording video the most critical is the best quality video capture. You may also need more sensitive than the built-in, microphone. Best image quality providing the camera by Logitech and Philips. The only inconvenience that may arise – is the need for constant connection with a computer cable and lack of a viewfinder.
Autofocus
Autofocus (or avtozum) is convenient because you do not have to manually configure each time focus. The camera with servo and clever electronics tune into razor sharp. Cameras with manual focusing is extremely rare.
Built-in microphone
Built-in microphone, now have almost all models of web-cameras. This is convenient, especially those that do not need to connect additional devices. And, of course, saves you time. The only nuance here may be that in most cases the sound quality of such microphones is not the best, so if you already have a good microphone is better to use them. Cameras with built-in microphone can transmit audio. Also, sound files can be transferred by the availability of audio channels in the cell.
Password protection
It occurs not in all models and serves to limit the rights of access to web-camera. By default, the video camera can be viewed from any networked computer that is equipped with a standard web-browser (eg, Internet Explorer or Netscape Navigator). However, you can limit the number of persons with rights of access to web-camera, enter the password to the user level. Many web-cameras support multi-level password protection for the separation of access rights and administration.
Motion Detector – is a software module for the detection of moving in the field of web-camera installations. The detector determines the size of the object and its speed.
Fixing the camera
By the method of the physical installation of the webcam can be divided into klipsovye and desktops. Klipsovye securely attached to your LCD monitor or lid. Such cameras are often quite petite, and sometimes even embedded in the monitor. Board, as the name implies, have a platform and a leg. Although they occupy with some useful space, but give greater freedom of choice in the direction of the point of shooting.
The monitoring system with web-cameras
Now web-camera more frequently used to organize surveillance systems. Few (or one, depending on the global system) cameras, installed in a room connected to a computer from which with the help of special software is tracking. It may conclude simply visual observation or in the auto-tracking of the movement (when the camera detects motion). Preparation of the monitoring system of web-cameras allows for relatively little money to organize the qualitative observation. Of course, there is this solution and its shortcomings. Primarily, this limitation on cable length USB – the maximum distance devices 5 meters.
Quality and price
Now we can summarize and highlight the main characteristics that are worth paying attention when buying a web-camera:
1. The maximum image resolution of 640×480 pixels.
2. USB-interface to connect to a computer.
3. Frame Rate – 30 fps.
4. Automatic adaptation to a wide range of lighting
Based on these criteria, you can choose web-cameras in different price categories.
In a series of cost-fall web-kamers with a resolution of 640 x 480 pixels, auto-focusing, without built-in microphone and the interface with USB 2.0. This option is ideal for home video and for novice users.
More discerning users recommend that you stop your choice on the web-camera with a resolution of 1600 x 1200 pixels, built-in microphone, who knows how to approximate the subject with a digital zoom, with the functions of automatic face tracking user. Typically, these devices support USB 2.0 and are equipped with advanced software.
The recognized leaders in the field of web-cameras are the companies Intel, Logitech, Microsoft, Philips, PerfectGift, Mustek, Genius, Creative.
How to organize a videoconference
Videoconference – this communication via the Internet in real time. In the process of communication the user has the opportunity to see how his companion, and his own image. In this part of the screen occupied by the window with the video picture, and in the remaining parts can be located windows applications to work together with the data. The quality of video is based primarily on the quality of the sound and picture. The first depends on the user’s ability to capture deviations or distortions (eg, noise or interruptions) in the stream of transmitted speech. Video quality is determined by the resolution of the image (number of dots per inch) and the frequency of the frame (the number of reproduced frames per second). For the viderkonferentsy suit almost all web-camera, it all depends on the requirements for image quality and breadth of the data link.
About the Author
Alex Keys 27y.o., California, USA
Can 2.46 volts kill an iPod? (line level to mic input test)
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