Task 2 - Video Fact File: PAL, NTSC and SECAM

PAL (UK – Phase Alteration Line) - PAL is the predominant video system or standard mostly used overseas. In PAL, 25 frames are transmitted each second. Each frame is made up of 625 individual scan lines. Regions which use PAL are Afghanistan, Australia, Belgium, China, Germany, Hong Kong, South Africa and the United Kingdom. People in the States may notice the slight flicker of a PAL video, having become used to the higher frame rate of NTSC, PAL offers noticeably improved resolution and color stability. After several minutes of viewing a PAL video, our brains compensate, and the flicker becomes un-noticeable.

NTSC (America – National Television Standards Committee) - NTSC is the video system or standard used in North America and most of South America. In NTSC, 30 frames are transmitted each second. Each frame is made up of 525 individual scan lines. NTSC has a lower resolution than PAL or SECAM but a faster frame rate, which reduces flicker.

SECAM (French - Sequental Color With Memory) - SECAM, SECAM aussi Written Which stands for Sequential Color Memory, French for "Sequential Color with Memory". SECAM WAS Developed in France and is Used in France and Its territories, much of Eastern Europe, Russia, the Middle East and northern Africa. This system uses the Sami resolution of PAL, 625 lines, and frame rate, 25 per second, the goal SECAM Processes way the color information is not compatible with PAL.

Task 2 - Video Fact File - Data Rate

Data rate – A data rate is the rate at which information being transferred. It is expressed in terms of amount of information per unit of time. For example, a common type of data rate used when describing the speed of a hard drive is Megabytes.

Another example would be kilobits, which is often used with compressed audio files. Once the consumer determines the data rate at which the information is being transferred, it becomes possible to figure out how much hard drive space they'll need to store the video.

KBPS – kilobits per second - A small "b" indicates a measure of bits, however, a large "B" indicates a measure of bytes. There are 8 bits within a byte.

For example:
4320KBps = approximately 34,000 Kbps
4320Kbps = approximately 500 KBps

Kbps stands for kilobits per second - thousands of bits per second and is a measure of bandwidth - the amount of data that can flow in given time on a data transmission medium.
Higher bandwidths are more conveniently expressed in megabits per second - Mbps, or millions of bits per second and in gigabits per second - Gbps, or billions of bits per second.

Task 2 - Fact File: TV Broadcasts

Terrestrial TV/Broadcasting

Terrestrial television is a television broadcasting which does not involve satellite transmission or cables. Terrestrial broadcasting uses radio waves through transmitting and receiving antennas or television antenna aerials. The TV signal was transmitted from a TV station, to an antenna on the side of a house, which was then transmitted to the consumer’s remote control.

Analogue television is the analog transmission that involves the broadcasting of encoded analog audio and analog video signal: the broadcast signal is a function of variations in the frequency of the signal. Analog television may be wireless or can require copper wire used by cable converters. Analogue terrestrial TV is available for free, apart from the BBC license fee, to 98.5% of UK households.  

Terrestrial Television started in the 1930s and lasted up until 2008. On the 12^th of December BBC 2 began to disconnect its analogue TV signal creating the ‘Digital Switchover’.

Digital Terrestrial TV

The purpose of digital terrestrial television is to reduce the use of spectrum and have more capacity than analogue, such as better-quality picture, and lower operating costs for broadcasts. A terrestrial implementation of digital television technology uses aerial broadcasts to a conventional television antenna instead of a satellite dish or cable television connection.

Advantages of Digital Terrestrial TV

·         Digital presentation tends to be better overall, with a good signal, due to the elimination of visible interference and other effects such as ghosting.

·         It is easier to obtain the digital picture than the analogue picture.

·         Interactive (red button) services can be provided.

Disadvantages of Digital Terrestrial TV

·         New equipment (set-top box) may be required.

·         Increased electricity equipment needed if both the TV and additional set-top boxes are plugged in.

·         An upgraded antenna installation may be required.

·         Digital signal transmission suffers from the cliff effect which means that once the signal lowers beyond a certain point, the receiver fails to decode the signal and cannot present the expected output.

Digital Terrestrial TV is transmitted on radio frequencies through terrestrial space in the same way as standard analog television, with the main difference being the use of multiplex transmitters to allow reception of multiple channels on a single frequency range known as subchannels.

Small-dish satellite systems are digital. The TV programs are encoded in MPEG-2 format and transmitted to Earth. The set-top box decodes the MPEG-2 format, then converts it to a standard analog TV signal and sends it to the consumers TV on channel 3 or 4

Digital Terrestrial TV Multiplexes

A multiplex is a range of TV services that have been digitized, compressed and combined into a single digital data-stream for transmission to the consumer over a single channel. A receiver separates each service from this compressed data-stream and is turned into a form which can be viewed. Anything that can be digitized can be contained in a multiplex. These include sound, video, text, computer applications, electronic programme guide information and upgrades.

The UK has six terrestrial multiplexes, the three public service multiplexes are BBC A, BBC B and D34. The three commercial multiplexes are SDN, ARQA and ARQB. Channel Five will move to a public service broadcaster multiplex at the digital switchover. After the digital switchover, the public service broadcaster multiplexes will provide coverage to 98.5% of households, while the commercial multiplexes will reach 90%.

Digital Terrestrial TV Transmitters -

Satellite TV – Sky

Satellite television is delivered by a communications satellite and received by an outdoor antenna, usually a satellite dish. Household generally uses a satellite receiver either in the form of an external set-top box or a satellite tuner module built into the TV set. Satellite TV tuners are also available as a card or a USB stick attached to a computer.

Satellite television starts with a transmitting antenna located at an uplink facility. Uplink satellite dishes are large, for example some are 30 to 40 feet in diameter. The greater the diameter, results in more accurate aiming and increased signal strength of the satellite. The signal path from the satellite to the stations/households on Earth is called the downlink.

Large-dish satellite antennas pick off unencoded or encoded signals being beamed to Earth by satellites. First, the dish is to be pointed at a particular satellite, and then the consumer selects a particular channel it is transmitting. The set-top box receives the signal, decodes it if necessary and then sends it to channel 3 or 4.

Digital Cable TV – Virgin

In the 1950s, there were four television networks in the UK. Because of the frequencies allotted to television, the signals could only be received in a "line of sight" from the transmitting antenna. People living in remote areas, especially remote mountainous areas, couldn't see the programs that were already becoming an important part of UK culture.

In 1948, people living in remote valleys solved their reception problems by putting antennas on hills and running cables to their houses. These days, the same technology once used by remote hamlets and select cities allows viewers all over the country to access a wide variety of programs and channels that meet their individual needs and desires. By the early 1990s, cable television had reached nearly half the homes in the UK.

Cable systems deliver hundreds of channels to some 60 million homes, while also providing a growing number of people with high-speed Internet access. Some cable systems even let you make telephone calls and receive new programming technologies.

The earliest cable systems were placed antennas with very long cables connecting them to subscribers' television sets. Because the signal from the antenna became weaker as it traveled through the length of cable, cable providers had to insert amplifiers at regular intervals to boost the strength of the signal and make it acceptable for viewing.

Virgin Media is a fibre optic broadband, which provides a wide range of unlimited broadband, TV and home phone packages and bundles including the fastest broadband in the UK with speeds up to 100Mb.

Virgin Media is one of the most well known names in the UK broadband, TV and phone business, and the foremost provider of fibre optic broadband to UK consumers. Virgin offers its fibre optic broadband, cable TV services by its own cable network. This means that Virgin customers don’t need a BT land line to subscribe to cable products, and they can have all charges including their line rental on a monthly bill.

Each of Virgin Media’s individual services have their own strengths and many of its 10,000,000 customers will just subscribe to one or two while others enjoy maximum convenience and value for money by opting for triple bundles of broadband, TV and phone.

Video gamers can battle online on Xbox, PS3 or Wii with little or no lag time, making a much more enjoyable online gaming experience. Virgin Media broadband also lets user’s stream movies and TV programmes at a faster rate than most other broadband providers therefore removing the delays caused by buffering.

 

 

Task 1 - 3 Ideas Powerpoint Presentation