Seminar

HDTV Technology

&

Scanning Techniques

Presented by : Anirudh Kannan

Topics to be Covered

• A/V Reception & Transmission

• Video & Audio formats

• Luminance, Chrominance & Loudness

• Pixels and Resolution

• Aspect Ratio

• Frames

• Scanning techniques

• 1080i or 720p or 1080p?

A/V Transmission and Reception(Broadcasting)

A/V Transmission or Broadcasting is the distributionof audio and video content to a dispersed audience via any audio or visual mass communications medium, but

usually one using electromagnetic radiation (radio waves).The receiving parties may include the general public or a

relatively large subset thereof.Broadcasting has been used for purposes of private recreation, non-commercial exchange of messages,

experimentation, self-training, and emergency communication in addition to commercial purposes like

popular radio or TV stations with advertisements.

A/V Transmission & Reception System

Video & Audio Formats

Audio Formats

• An audio file format is a file format for storing digital audio data on a computer system. This data can be stored uncompressed, or compressed to reduce the file size. It can be a raw bit stream, but it is usually a container format or an audio data format with defined storage layer.

• Some of the major Audio Formats used for broadcasting and transmission are WAV, MP3, AAC, FLAC, m4a, wma

Video formats• Uncompressed video delivers maximum quality, but with a very

high data rate. A variety of methods are used to compress video streams, with the most effective ones using a Group Of Pictures (GOP) to reduce spatial and temporal redundancy.

• Broadly speaking, spatial redundancy is reduced by registering differences between parts of a single frame; this task is known as intra-frame compression and is closely related to image compression. Likewise, temporal redundancy can be reduced by registering differences between frames; this task is known as inter-frame compression, including motion compensation and other techniques.

• The most common modern standards are MPEG-2, used for DVD, Blu-ray and satellite television, and MPEG-4, used for Mobile phones (3GP) and Internet.

Luminance, Chrominance & Loudness

In scientific terms, the brightness of light is measured in terms of Luminance or Luma. The word ‘Luminance’ is directly defined by CIE in relation to human vision. It is represented by the letter Y as far as video is concerned.

Chrominance or chroma represented by C is the signal used in video systems to convey the color information of the

picture, separately from the accompanying luma signal (or Y for short).

Loudness is the characteristic of a sound that is primarily a psychological correlate of physical strength (amplitude).

Luminance only, Chrominance only & Full Color Image

Frames, Pixels & Resolution

The quality of a display system depends on it’s resolution, how many pixels it could display and how many bits are

used to display each pixel!

Frame• In filmmaking, video production, animation, and

related fields, a film frame or video frame is one of the many still images which compose the complete moving picture.

• When the moving picture is displayed, each frame is flashed on a screen for a short time (nowadays, usually 1/24, 1/25 or 1/30 of a second) and then immediately replaced by the next one. This is called Frame Rate. Persistence of vision blends the frames together, producing the illusion of a moving image.

Pixels

• Pixel or picture element is a physical point in a bitmap image or the smallest addressable element in all points addressable display device, like TV/computer screen. Hence, it is the smallest controllable element of the picture represented on the screen.

• Monitors/Screens display pictures by dividing the display screen into thousands or millions of pixels, arranged in rows and columns. The pixels are so close together that they appear connected.

• The number of bits used to display each pixel determines how many colours or shades of grey can be displayed. Eg. In 8-bit color mode, the color monitor uses 8 bits for each pixel, displaying 2^8 or 256 different colours

Rough Idea of Pixels!

Resolution• The display resolution of a digital television, computer monitor or display device is

the number of distinct pixels in each dimension that can be displayed. It can be an ambiguous term especially as the displayed resolution is controlled by different factors in cathode ray tube (CRT), flat-panel display which includes liquid-crystal displays, or projection displays using fixed picture-element (pixel) arrays.

• It is usually quoted as width × height, with the units in pixels: for example, "1024 ×768" means the width is 1024 pixels and the height is 768 pixels. This example would normally be spoken as "ten twenty-four by seven sixty-eight" or "ten twenty-four by seven six eight".

• High-definition television (HDTV):

– 720p (1280 × 720 progressive scan)

– 1080i (1920 × 1080 split into two interlaced fields of 540 lines)

– 1080p (1920 × 1080 progressive scan)

• CRT television:

– 480i (Analog system of 486i split into two interlaced fields of 240 lines)

– 576i (720 × 576 split into two interlaced fields of 288 lines)

Aspect Ratio

Aspect ratio describes the dimensions of video screens and video picture elements. All popular video formats are rectilinear, and so can be described by a ratio between width and height. The screen aspect ratio of a traditional television screen is 4:3. High definition televisions use an aspect ratio of 16:9.

The aspect ratio of an image describes the proportional relationship between its width and its height.It is commonly expressed as two numbers separated by a colon, as in 16:9. For an x:y aspect ratio, no matter how big or small the image is, if the width is divided into x units of equal length and the height is measured using this same length unit, the height will be measured to be y units.

Lets See How The HDTV looks like as compared to standard

definition TV!

4:3 Aspect Ratio in CRT TV 16:9 Aspect Ratio in HDTV

4 units

3 u

nits

16 units

9 u

nits

Scan Video Signals

Video signals are of two types1. Progressive Scan Video

Video sources that are listed with the letter p are called progressive scan signals. Examples of this would be 480p, 720p

or 1080p. Progressive scan video content displays both the even and odd scan lines at the same time

2. Interlaced Scan VideoVideo sources that are listed with the letter i are called

interlaced scan video. An example of this would be 480i or 1080i. Interlaced video displays even and odd scan lines as separate

fields. The even scan lines are drawn on the screen, then the odd scan lines are drawn on the screen. Two of these even and odd

scan line fields make up one video frame.

Interlaced Scan

Progressive Scan

Interlaced & Progressive Scan

Progressive or Interlaced!

• The advantage of progressive scan is clearer picture with more detail, contrast and crisper lines. This is achieved because the entire picture is on the screen at once.

• The primary drawback to progressive video, at least until very recently, was the higher bandwidth requirement. It requires double the bandwidth required by interlaced Scan. Higher the bandwidth higher will be the cost.

• The main benefit of interlaced video is that it allows more detailed images to be created than would otherwise be possible within a given amount of bandwidth

• interlaced video comes with real-world downside, including image softening that occurs during fast-motion sequences as well as strobing effects that sometimes appear when striped shirts, plaid jackets, bricks in a building, or similar types of objects are shown

Conclusion: 1080i or 720p or 1080p?

1080p!

• Using progressive 1080p with 60 full frames per second in the future has a potential to eventually solve the problems of interlaced scan or 1080i but it will require a whole new range of studio equipment including cameras, storage and editing systems which are coming up soon.

• Currently the only way to have a fluid motion with progressive scanning in most countries is 720p that has a frame rate that is two times faster than 1080p but the resolution of only 1280 × 720 pixels (instead of 1920 × 1080 pixels) which may be a problem for some applications and you will have to compromise with the screen resolution!

• In fact, all digital, non-CRT displays are natively progressive, and any interlaced video signals they receive must be converted, or "de-interlaced", to the progressive format before they can be displayed.

If your are going to buy a new HDTV in near future, go for a 1080p!!