Video sender
A video sender (also known as a DigiSender, wireless video sender, AV sender or audio-video sender) is a device for transmitting domestic audio and video signals wirelessly from one location to another. It is most commonly used for sending the output of a source device, such as a satellite television decoder, to a television in another part of a property and provides an alternative to cable installations.
A wide range of video sender technologies exist, including
Video senders have been a frequent cause of
Overview
Typical video sender applications include the transmission of television audio and video signals from a lounge to a bedroom or from a CCTV camera to a display, as well as interconnecting appliances with audio, video and Internet Protocol (IP) requirements.
Most video sender systems will consist of three separate components, a
As connectivity standards have changed in the television and audio-video markets, so it has in the video sender market, with older models usually featuring SCART and/or composite video and newer models featuring HDMI as their key means of connection to host equipment.
Analogue Wireless
Analogue video senders have the advantage of low manufacturing costs as the audio and video signals are simply
Usually there are four FM transmit channels, A, B, C & D, with
The reverse remote control channel is usually fixed at 433.92 MHz, using whatever modulation is on the 34 kHz to 45 kHz IR remote "carrier". ASK/OOK schemes such as RC5 and RC6 work best over the RF link as the receiver uses a data slicer and AGC designed for ASK/OOK with
Analogue wireless video senders can achieve typical operating distances of up to 60 metres (200 ft) (clear line of sight) with DVD quality (720x576) video resolution and stereo audio.
Digital Wireless
Digital video senders are quickly becoming the most popular solution and combine the use of a
Early digital video sender models typically transmitted in DVD quality, but more recent models are capable of achieving 720p and 1080p high-definition resolutions.
Spread-spectrum
Spread-spectrum techniques are methods by which a signal is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth. Within the video sender market, these techniques allow for a wireless signal to be transmitted with much less chance of interference from, and to, local Wi-Fi networks.
It is not uncommon for several Wi-Fi networks to be within range of a typical home and as such, spread-spectrum based video senders are often the best solution for transmitting audio and video signals within this crowded wireless environment.
Some manufacturers use proprietary spread-spectrum techniques, enabling typical operational ranges of up to 80 metres (260 ft) in-building. By also employing externally mounted antennas, operational ranges in excess 2,000 metres (6,600 ft) (clear line-of-sight) have been achieved and several such models are sold under the Digi-Sender brand.
Wi-Fi
Video senders that operate on existing Wi-Fi networks have recently been developed and provide another interference free method of transmitting audio and video. Bandwidth over the Wi-Fi network will be shared between the video sender and all other connected devices, which can cause issues when used with older networking technologies, however this is not a problem with more recent
Ultra-wideband
Ultra-wideband is a technology for transmitting information spread over a large bandwidth (>500 MHz) and is generally used for short-range applications (typically 10 metres (33 ft) or less) where a simple link is required from the source device to a monitor or television. As such, it is generally unsuitable for video sender applications that would require a signal to be sent to another room.
Digital Wired
Several video sender technologies, such as power-line communication and HDBaseT, now exist that make use of existing networks, providing a wired video sender solution for distributing audio, video and internet connectivity around the home.
Power-line communication
Video senders using power-line communication make use of existing mains electricity circuits to send the audio and video signals. This provides similar benefits to a wireless video sender i.e. no additional cabling, as well as the ability to transmit in high-definition and even ultra-high-definition resolutions.
HDBaseT
In 2010 a new standard for cabled applications was released called HDBaseT a
Legality
There are several issues which relate to the
Transmitting via radio within a home
Transmitting signals wirelessly requires the product to be tested to relevant standards for wireless license exemption, these products are generally limited to 100 mW (10 mW in the UK) and for higher power models, used generally within the broadcasting industry, a licence is required. If the broadcast is across LAN or via similar IP technologies, such as the internet, then using streaming technology does not require a license. The regulator is the Federal Communications Commission (FCC) in the United States who are responsible for the efficient use of radio bandwidth.
Copyrighted programme material
A subscriber may wish to distribute TV to other televisions in the home and there is no limit to the number of TVs that can display the same signal. How the subscriber chooses to distribute his TV signals within his home is constantly changing. With an increasing number of TV displays around the home and a need for greater resolution the options continue to grow. Users are permitted to distribute copyright material provided it is being viewed by the
Enforcement
Agencies responsible for the enforcement of wireless telegraphy equipment are as follows:
- United Kingdom: The telecommunications and postal industries of the United Kingdom.
- United States: The Federal Communications Commission (FCC) regulates interstate and international communications by radio, television, wire, satellite and cable.
- Germany, The Federal Network Agency (German: Bundesnetzagentur or BNetzA) is the German regulatory office for electricity, gas, telecommunications, post and railway markets.