Deakys Guide's to Audio/Video

In the beginning, all signals went through the RF (radio-frequency, or antenna) input. An RF TV signal contains luminance (black and white), color, and audio signals all mashed together in a complex way that the TV set has to sort out before delivering picture and sound. It’s not a pretty process–something is always lost in the translation–but there is no avoiding it with broadcast TV.

Widely used in Europe the 21-pin SCART connector has been around since the late 80’s It can carry Composite, S-Video or RGB video signals as well as stereo audio. It also has pins reserved for data switching which are today used for such as auto 16:9 Widescreen switching and smart systems for control video recording devices.

Composite Video
Term used to describe systems that output all colour, sync and black levels down one cable. Avoid using this type of signal at all costs. :wink:

SVHS/S-Video (Y/C)
S-video simply means separated video.The brightness (Y) and color © signals carried by separate wires within the cable. (Hence, another name you may see for S-video is Y/C.) Since the signals are never combined, they don’t need to be separated. That’s a benefit because the process of combination and separation is never perfect, losing detail and creating subtly (or sometimes not so subtly) annoying errors, such as dots crawling along sharp edges or moiré effects on tightly patterned fabrics.

RGB Video
RGB stands for Red Green and Blue, these are the 3 colours used to display a TV picture. Using RGB the picture is sent as three separate colours corresponding to the three colours used in a TV to display the picture. A high resolution RGB picture can have a bandwidth of over 10MHz and this is without doubt the best way to send picture information to a TV or display. RGB requires a seperate timing signal. This can be sent seperately -RGB+s or more commonly down green RGsB. Green is used because our eyes are less sensitive to green and therfore less likely to perceive any degredation in the signal.

This is basically the same as RGB above but the sync signals are seperated into their native horizontal and vertical components and are also slightly higher voltage, making them suitable for longer cable runs. This method of connection is used to connect pc’s to their monitors and plasma screens to video processors etc. RGB+HV requires no further processing by the tv to display the picture

Component Video (Y/U/V) (Y/Pr/Pb)
A high quality video connection found on video sources like DVD and of course on display devices like plasma, projection etc. Component Video can also be used for carrying the signal when DVD players have Progressive Scan output Labelled as “Y” “Pr” and “Pb”. “Y” is luminance, luma, or “Brightness” This describes the level of white (or black). “Pr” is the level of Red “Pb” is the Level of Blue The green section of the final colour output is derived from the levels of red, blue and white level, whatever the difference present in the the white level after subtracting blue and red must be green. This is the format used to store video information on DVD’s.

Nicam Stereo
NICAM is the digital stereo sound system used in the United Kingdom for normal terrestrial analogue broadcasts developed by the BBC. NICAM is a data compression system for encoding and decoding sound at speed (So as to avoid lip-sync) It works at a 32kHz Sampling frequency and so has a reduced audible frequency range (15Khz) compared to other digital formats such as CD or MPEG audio although it is less compressed at it is transmitted at a bitrate of 704Kbps

Dolby Pro-Logic
The most widely used Home Entertainment process. Produces a surrounding sound field with Dolby Surround or Dolby Stereo encoded software. This includes practically all major films from the late seventies and onwards available on VHS videotape, LaserDisc, DVD or from stereo TV. It has 4 perceivable channels of sound all derived from a stereo sound track, (Left Front, Centre, Front Right and Rear Surround) This is achieved by redirecting out of phase information (Normally deliberately encoded in to the stereo tracks) to the rear speakers. Information going to the centre channel (Pro-Logic) processes and mixes all information that is lacking in any stereo content Dolby Pro Logic 2 is the updated version of Pro-Logic that gives stereo surround speaker channels .

Dolby Pro-Logic 2
Pro Logic II decoding reproduces 5.1-channel surround sound from any 2-channel sources: DVD, VHS, television broadcasts, radio, and CDs. Dolby Pro Logic II uses matrix decoding technology that has been dramatically improved over ordinary Pro Logic. With Pro Logic II, for instance, the Surround (Rear) channels are in stereo (only mono with Pro Logic) and playback covers the full frequency range (only up to 7 kHz with Pro Logic). These improvements let you enjoy a wide variety of 2-channel sources with the exciting effects of 5.1- channel surround sound. It’s not as good as discrete (Separate independent channel) formats like Dolby Digital and DTS, but it’s more involving than ordinary stereo and a much better home cinema experience than Dolby Pro Logic

Dolby Digital
Dolby Digital produces 5 discrete (perfectly separated) sound channels and a dedicated LFE (Low Frequency Effects) subwoofer channel. For this reason it is known as a 5.1 channel system (the .1 indicating the subwoofer channel that has limited frequency for just the low audio frequencies) Dolby Digital has all the benefits of an all digital system in terms of clear sound without distortion and noise. Compared to Dolby Pro Logic, the sonic improvement almost corresponds to stepping up from cassette tape to CD Dolby Digital is used in a variety of video/audio formats world wide including. DVD, Laserdisc, Computer Games, Radio and TV broadcasting. Dolby Digital was originally known as AC-3, this is still the name of the encoding used.

Dolby Digital EX
Dolby Digital EX adds a centre-surround channel to the existing 5.1 set-up… Dolby Digital EX is the mixing of mono content from the two stereo rear speakers into the rear surround channel in a similar way to DTS-ES Matrixed However it is not discrete so not a true 6.1 system like DTS-ES Discrete

DTS produces 5 discrete (perfectly separated) sound channels and a dedicated LFE (Low Frequency Effects) subwoofer channel. For this reason it is known as a 5.1 channel system (the .1 indicating the subwoofer channel that has limited frequency for just the low audio frequencies) DTS has all the benefits of an all digital system in terms of clear sound without distortion and noise. DTS is used in a variety of video/audio formats world wide including. DVD, Laserdisc, Computer Games, Radio and TV broadcasting. DTS boasts a higher bitrate than its competing format Dolby Digital and therefore can provide higher sound quality (Due to there being less compression)

DTS Extended Surround adds a centre-surround channel to the existing 5.1- channel set-up. DTS-ES brings these soundtracks into the home in DTS quality and is the only home format that can deliver all 6.1-channels discretely. All sounds will be heard, whether played back as discrete, matrix or on a 5.1 system. It is is compatible with all DVD-Video players and is accessible through the digital output. The DTS coding system has a “core + extension” structure. The “core” represents the DTS data as has been known since the first home decoders. The “extension” can carry data for future applications or enhancements of any sort. All DTS decoders recognize and use the core data. Basic decoders ignore the extension data, while advanced decoders can make use of it. The extension for DTS-ES Discrete carries the additional 6th channel and is totally independent of the other channels. DTS-ES Matrixed is the mixing of mono content from the two stereo rear speakers into the rear surround channel in a similar way to Dolby Digital EX

DTS-ES Discrete 6.1
A new 6.1 channel surround sound format. The extra channel is intended to drive one or more ‘back surround’ or centre rear speakers located between the left and right ones. The sixth channel with be ‘ignored’ by the regular 5.1 DTS decoders, hence the need fir DTS ES Matrix 6.1 This Format like Dolby Digital EX encodes the back surround channel via an analogue matrix, and delivers it via the rear channels.

On a standard CRT-based television, the video image is created by sweeping an electron beam across the face of the set where it excites phosphors, causing them to glow. The television changes the intensity of the beam to vary the brightness of the image. If you look closely at the picture on a television set, you will see the horizontal scan lines that make up the image.

The standard video signal in the UK (officially referred to as the PAL standard) consists of approximately 280 visible horizontal scan lines per video field, with fields occurring 50 times per second. When this standard was originally conceived, the average television was relatively small so a typical viewer would not be able to pick out the individual scan lines but would instead see what appears to be a smooth picture. However, as televisions have grown larger in size, these lines have become more noticeable, and with large televisions and projectors,they have become an annoying element of the image.

Video Line Doublers were originally conceived to try to address this issue by increasing the number of lines scanned across the face of the display. It is not simply a matter of drawing more lines. To understand how a modern line doubler works, it is necessary to understand the difference between interlaced and progressive scanning.

Interlaced scanning is used in today’s standard analog televisions. An interlaced TV “paints” the lines of a frame in two separate passes. Half of the lines are drawn in the first pass (the even lines), and the other half (the odd lines) are drawn in the second pass. First devised so that early TVs could have reasonable resolution with the limited transmission technologies available at the time, interlaced scanning has several unfortunate side effects.

The first major problem with interlaced scanning is that the image may visibly flicker if the screen is large enough that it represents a significant portion of the viewing angle. Even with small screens, sharp edges on objects may flicker. This effect is due to the fact that only every other line is drawn on each pass, causing hard edges to appear to move up and down on each field. In addition, more problems are caused by the fact that neighboring horizontal lines are from two different fields,that is, they were not captured by the video camera at the same time and they are not drawn on the screen at the same time. If motion occurs during the time between these two fields, the edge of the moving object will appear to be very jagged. This jagged edge is usually not noticeable to most television viewers because as the new field is being drawn, the “older” field is fading in intensity. However, on high-resolution displays or on devices such as Liquid Crystal Displays (LCDs) or plasma panels that do not fade, an interlaced image will contain noticeable motion artifacts.

These types of effects are the reason that a line doubler can’t simply repeat each of the incoming lines and expect the output image to be acceptable. Instead a doubler will first have to fully “deinterlace” the image, removing the motion artifacts described above while still retaining as much detail as possible.

Deinterlacing is the process by which interlaced video is converted to progressively scanned video. Progressive scanning paints all of the lines of a frame in one top to bottom pass. This is used where transmission bandwidth is not an issue and where the highest quality image is required. None of the interlaced side effects are present with progressive scanning. Devices for performing deinterlacing are available for around £100 for low-quality techniques or for many thousands for very sophisticated techniques. The low-cost techniques are frequently used in progressively scanned TVs or projectors. High-quality algorithms capable of generating very high-quality video are typically used in line doublers designed for high-end home theater markets. Some very inexpensive deinterlacers simply put fields together, creating an output frame containing even lines from one point in time and odd lines from 1/50 second later. Any motion between these two fields will result in the motion artifacts described above.

To avoid these artifacts, some deinterlacers simply scale each of the fields up to the entire frame size, interpolating between the existing lines. Unfortunately, this also significantly reduces the vertical resolution of the image, resulting in softening of the picture and a loss of image detail. One method of avoiding this softening is to determine if there is any movement between fields by comparing each of the fields with its counterpart in a previous frame. Further refinement of this algorithm would be to apply the softening filter only to portions of the image that are in movement. This is referred to as “motion adaptive” deinterlacing.

Many line doublers can also take advantage of the “3:2 pulldown” technique that is used to transfer film to video. During this transfer, the first film frame is captured onto 2 video fields (first even lines, then odd lines are scanned), then the second film frame is captured onto 3 video fields (even, odd, even). As this is repeated, you can see that two 24Fps film frames (for a total of 1/12 of a second) are captured onto five 60fps video fields (for a total of 1/12 of a second). A deinterlacer can examine a series of fields to detect this sequence and thereby determine that the original, pre-video source of this sequence was film. It can then reassemble the original progressive frames from the partial interlaced fields with no loss of resolution and with no introduction of motion artifacts.