6Video technology

Video devices include cameras and camera systems, consumer electronics, video recorders, streaming, and systems for recording and sharing content. They addressed in the following chapter.

Schematic of the CCTV system in a TV studio

Cameras and camera systems form one large area of ​​video technology. The basic division includes three main categories:

1. installation cameras

- Rotating PTZ (Pan, Tilt, Zoom) - this type of camera is equipped with motor or manual rotation in the horizontal and vertical axis. In addition, it is possible to modify the so-called zoom lens. It is perfect for rooms where flexible image capturing is required in varying conditions such as person tracking, detail shots, overview, etc. The camera can be controlled from a console, a computer, or the control system. If the camera is part of, for example, a videoconferencing system, its motion can be controlled by an intelligent processor that detects faces and human voice. The camera then focuses on the speaking person.
- Cameras with the fixed mount - cameras of this type are designed for situations where you need to scan a specific place in a room or a wide view of the whole area is needed. They are used when conditions in the room are fixed and people in front of the camera do not move. These cameras can be equipped with a fixed lens or a zoom lens.
- Webcams – they are used to be connected to a computer or a conference system using the USB (Universal Serial Bus) interface. The purpose is to capture an individual or a limited number of people in an image and transfer it to further processing. Typically for Skype conferences, WebEX, etc. They can also serve to capture static images, i.e. photos.

Examples of installation cameras

2. portable cameras

- professional - they are used mainly in television and film industry. They can also be used in regional or corporate studies where a user requires high image quality. The price range of these cameras starts roughly at 100,000,-. The best cinematography cameras are very expensive that the film producer usually leases them for a specific project.
- consumer - commonly available cameras for the widest range of users. They typically find use in households and in low-cost projects where the low price plays a role. Most features are fully automatic and a user needn’t have any deep knowledge on image processing. However, even in the category of consumer cameras, there are models for demanding users, which can be classified as semi-professional. They provide a variety of features to set the parameters manually, resulting in high quality image quality.

Examples of portable cameras

3. special cameras

- purpose - cameras in this category are made for specific purposes. E.g. for thermal analysis, sensory detection (motion sensors, keying, ...), slow motion
- inspection - different types of cameras for medicine and other technical fields. They are used to transmit images from difficult-to-access or life-threatening places
- industrial - this category includes cameras used in various areas of industry

Examples of special cameras

In addition, cameras and camera systems can be divided by Interface to Digital (HDMI (High-Definition Multimedia Interface), DVI (Digital Visual Interface), SDI (Serial Digital Interface)), IP (Internet Protocol) for Ethernet Streaming, USB and combined (may have different interface combinations from the mentioned above).

Consumer video products include DVB (Digital Video Broadcast) receivers, TVs and DVD/Blu-ray players and recorders. These products are used in AV/IT installations as complementary to the system, not as the main solution. Consumer electronics is characterized by a low service life (i.e. no 24/7 operation), limited functionality for integration with other AV components, limited support by the manufacturer or distributor, often changing assortment.

Video recorders are video recording equipment for conventional recording, they can be divided into single channel and multichannel recorders, or similarly to cameras, according to the type of available interfaces.

Nowadays, a very interesting and popular application area is Streaming.

Streaming is a continuous audiovisual technology for transfer between the source and the end user. At present, streaming is mainly used for transmission of audiovisual material over the Internet (Webcasting). Webcasting can take place in real-time (Internet TV or radio) or as VoD (Video on Demand) – e.g. YouTube. To stream video to multiple users at the same time, the operator must have a stream server (in addition to the content) that communicates with target computers and streaming data.

For the transmission of audiovisual material over the Internet, codecs are used to reduce the volume of transmitted data. Flash codecs, MPEG-4 (Moving Picture Experts Group-4), Windows Media, Real Time and QuickTime are the mostly used codecs. Even so, transmission of the TV resolution video (720×576) is very demanding. Therefore, streaming at 320x240 pixels at 256 to 512 kbps was the most popular. Nowadays, we can quite commonly encounter extremes such as 4K streaming, offered for example by YouTube or Netflix.

Streaming audio primarily uses WMA (Windows Media Audio), MP3, OGG, and AAC+ (Advanced Audio Coding+) codecs in data streams, typically from 16 to 256 kbps. Audio can be streamed as singlebitrate, i.e. either a constant bitrate or multibitrate, which is a number of constant data streams transmitted together in one data stream between the encoder and the server. A player that can play multibitrate stream from the server can then automatically change the sound quality if the Internet connection deteriorates/improves.

The distribution of AV stream to the viewer is basically possible with three basic methods:

- Unicast - the transfer takes place in a closed circuit between two points, i.e. a source and a viewer. This method is suitable for transfer over backbone paths or between clearly defined products. Only one viewer can be connected to each source at a time. Multiple unicast on the network must be arithmetically aggregated and define the overall data stream of the system.
- Multicast - in this method, it is possible for multiple viewers that more users can join one stream at a time. The stream is started by a demand from the viewer towards the signal source. Viewers whose stream is turned can capture it based on the connection with the source. On the contrary to unicast, multicast streams do not accumulate, there is just one stream in the network. However, multicast traffic is only available on a controlled network with active Layer 3 Switch activation constraints
- Broadcast - is methodically similar to multicast, with the difference that the stream source actively transmits to all endpoints in the network. It is the least used of the three methods, since it cannot be controlled and thus the network can potentially encounter huge data overload

Apart from the above-mentioned video and audio distribution to the Internet, Streaming is also used in AV systems. In this case, bitrate is not a critical issue - it can use the full bandwidth offered within the local LAN, which can be up to 1 Gbps. However, one of the codecs must be used here as well, which compresses the signal and reduces the data stream. The uncompressed 1080p signal can easily reach up to 10 Gbps.

The most common codecs are in H.264 and JPEG2000. However, manufacturers produce a number of custom codecs, which are, however, mostly compatible with only one brand of products. Codecs can either be in the form of hardware or they are installed as software on a dedicated computer. In addition to image and sound, the selected codecs can also transmit other data, such as data for keyboard, mouse, USB peripherals, IR (InfraRed) and RS232 (Recommended Standard 232) signals, etc. It is therefore possible to transmit complex data over a single UTP cable within a computer network for data processing in the AV system. Some peripherals can also be powered on the same cable (PoE technology).

In association with AV content streaming, it is also worth mentioning the concept of CDN (Content Delivery Network). It is a network that provides broadcasting of an AV content by broadcasting to public or private networks. In essence, this is similar to DVB-T (Digital Video Broadcast - Terrestrial) or DVB-S (DVB-Sattelite), but takes place in an IP network environment. Providers are paid. Availability, capacity and archives are guaranteed for a fee. Custom CDNs are often run by large organizations.

Their traffic is expensive (for example, Mediasite EVP Server (Event Visualization Platform Server)).