Overview Of Video Recording, Editing And Broadcast Technology

Introduction

Broadcasting is a form of communication; it disseminates video and audio contents to receiving audiences. A TV standard can be defined as the format used in different countries so as to be able to view playback or to broadcast content. The three main analog television systems in use today around the world are NTSC, PAL, and SECAM. One luma signal and two chroma signals make up a video signal – the luma contains information about black and white video; while chroma contains additional information for black and white video to be converted to colour video. The bandwidth of luma and chroma signals is limited to particular values – the spectra of the chroma signal has a much narrower bandwidth than luma spectrum.

NTSC

The initials NTSC stand for National Television System Committee - it is responsible for setting television and video standards and DVD playback in the United States, Japan, Canada and Mexico. However, the dominant TV standard is PAL and SECAM – the NTSC is a much older TV standard. Created as a standard in the United States of America in 1941 - essentially for black and white television broadcasting - NTSC is the oldest broadcasting standard. It consists of 525 horizontal lines of display and 60 vertical lines; and uses a screen resolution of 720 by 480 pixels. It has a refresh rate of 30 Hz, much lower compared to PAL, which uses a screen resolution of 720 by 576 pixels - whilst having a lower refresh rate of 25 Hz. One advantage of NTSC compared to PAL is that it has a smoother image and a higher refresh rate- however, it is still not as high quality as PAL.

PALPAL is an abbreviation for Phase Alternating Line and can be considered the video standard – it is an analogue TV colour system. In the USA NTSC is used instead. PAL is mostly used the following countries: UK, large parts of Western Europe, many parts of South American, Asian, African, the Middle East and Pacific region. The screen resolution used in PAL is 720 by 576 pixels, with a refresh rate of 25 frames per second (FPS). When we compared it to the much older NTSC standard - the later has uses a lower resolution of 720 by 480 pixels and has a higher refresh rate of 30 frames per second. This allows PAL to have a greater picture quality than NTSC. However, even though NTSC has a smoother picture - PAL is more popular because of its higher picture quality due to having more pixels than NTSC.

SECAM

SECAM is an abbreviation for Séquentiel couleur à mémoire - which French for Sequential Colour with Memory. It is an analogue colour TV system which was first used in France in the early 1960’s, and is still used. SECAM is similar to PAL- it is based on a 50Hz refresh rate and runs on 625 lines. It uses the same bandwidth as PAL – however, it differs in that it transmits the colour information sequentially. Analog SECAM television cannot be easily edited, like NTSC or PAL, in its original form - post-production has seen used using PAL; which then has to be trans-coded into SECAM at the point of transmission. SECAM is similar to like PAL in that it consists of 625 vertical lines with 50 horizontal lines on a display. However, different types use different video bandwidth and audio carrier specifications. There are different types of broadcast systems are listed below:

1. Teletext – it was originally developed in the 1970’s - essentially to relay information such as news, weather reports and TV program schedules. It can be described as a system that adds the data into the blanking interval of an analog television signal.
2. AM Broadcasting – AM or Amplitude Modulation can be described as long, medium and shortwave signals that can travel across the large distances for worldwide broadcast services.
3. Analogue FM broadcasting - is an audio broadcast system – it is of a higher quality than AM radio.
4. Digital broadcast systems - radio and television broadcasting networks have become digitalized and have had revolutionary impact on the broadcasting world.

Digital Video Technology

Sound is stored and manipulated as a stream of discrete numbers in a digital recording system - each number representing the air pressure at a particular time. Analog To Digital Converter, or ADC numbers are generated by a microphone connected to a circuit. The digital video technology (DVR's) receives the television signal through it’s the built-in tuner through antenna, cable or satellite. If the signal is received through an antenna or cable, it passes into an MPEG-2 encoder. This converts the data from analog to digital. MPEG-2 is the compression standard used to fit information onto a DVD - it is widely used as the format of digital television signals broadcast terrestrially, through cables or directly by satellite systems. It also specifies the format and other programs distributed on DVD format – TV stations, TV receivers, DVD players, etc., tend to be designed to this standard. From the encoder, the signal is transmitted to two different places. Initially, it is transmitted to the hard drive for storage, and then to an MPEG-2 decoder. This then converts the signal back to analog and sends it to the television for viewing. The output of the ADC and the input of the DAC consists of a bundle of wires, which carry the numbers that are the result of the analog to digital conversion. These numbers are in the binary number system in which only two characters are used, that is 1 and 0.

Digital sound recording is a method of capturing and preserving sound in which audio signals are transformed into a series of pulses. These pulses correspond to patterns of binary digits, that is either 0’s and 1’s- they are recorded as such on the surface of a magnetic tape or optical disc. A digital system samples a sound’s wave form, or value, several thousand times a second. It signs a numerical value in the form of binary digits to its amplitude at any specific time. A typical digital recording system is equipped with an analog-to-digital converter which is responsible for transforming two channels of continuous audio signals into digital information – this is then recorded by a high-speed tape or disc machine. A digital-to-analog converter is used by the system which reads the encoded information from the recording medium and changes it back into audio signals – these can be used by the amplifier of a conventional stereo sound system.