TELEVIZIUNEA IN CULORI(incepatori+avansati)

[gessle]

Inainte de a vă conecta dispozitivele...
n partea din spatele a dispozitivelor video şi audio, veţi găsi următorii conectori, in funcţie de modelul deţinut:
Nume* Aspect Calitate Semnal transmis
HDMI ***** imagine + sunet

DVI ***** imagine

Video component ****(*) imagine

SCART **(*) imagine + sunet

S-Video ** imagine

Video Composite * imagine


Coaxial Digital ***** Sunet

Optic Digital ****(*) Sunet

[gessle]

* Pentru fiecare tip de conexiune, este folosită o culoare pentru a face diagramele mai uşor de inţeles.
Pentru a vă bucura de cea mai bună experienţă audio-vizuală cu ajutorul sistemului dvs., este de preferat să conectaţi cele mai bune dispozitive la conexiunile de cea mai inaltă calitate disponibile. De exemplu, player-ul Blu-Ray Disc sau Integratorul HD cu HDMI, urmat de player-ul DVD cu Component, apoi video-casetofonul cu S-video etc.
Notă : calitatea imaginii mai depinde foarte mult de calitatea cablului folosit.
HDMI Interfaţa Multimediade inaltă definiţie (HDMI) este o interfaţă audio/video integrală capabilă să transmită semnale video şi audio de inaltă definiţie. HDMI furnizează o interfaţă intre orice sursă audio/video digitală compatibilă, cum ar fi integratorul, un player DVD, un calculator, un sistem de joc video, sau un receptor AV, şi un monitor audio/video digital, cum ar fi televiziunea digitală (DTV) DVI Interfaţa Vizuală Digitală poate transmitevideode inaltă definiţie, dar nu transmite şi sunet. Va trebui să folosiţi conectorii audio ai dispozitivului dvs. (de obicei, digital optic/coaxial, sau RCA).
Este posibil să conectaţi un dispozitiv HDMI la un dispozitiv DVI folosind un HDMI la adaptorul DVI Video Component Video Component este o conexiune analogă. Este capabilă să transmităsemnalede inaltă definiţie. Component nu transmite sunet. Va trebui să folosiţi conectorii audio ai dispozitivului dvs. (de obicei, digital optic/coaxial, sau RCA) SCART Conexiunea SCART este un standard european care adună tipurile variate de semnale analoage comune, cum ar fi RGB, S-Video şi Composite intr-un singur conector. Aceasta poate transmitesunet şi videode inaltă definiţie. totuşi, calitatea imaginii este inferioară faţă de HDMI, DVI, şi video component. Nu poate transmite decat semnale cu definiţie standard S-Video Video Separat, pe scurt S-Video, cunoscut şi sub numele Y/C, este un semnal video analog care transmite datele video ca două semnale separate (luminozitate şi culoare), spre deosebire de video composite care transmite intregul set de semnale intr-o singură linie de semnale. Conform celor mai dese implementări ale sale, S-Video, transmitevideocu definiţie standard. Nu transmite semnale audio pe acelaşi cablu. Acest conector nu este reprezentat in cadrul diagramelor noastre de conectivitate Video Composite Video Composite este un format video (nu sonor) analog. Acesta este conectorul pe care trebuie să-l folosiţi dacă nu aveţi la dispoziţie alt conector, in ceea ce priveşte calitatea. Acest conector nu este reprezentat in cadrul diagramelor noastre de conectivitate Coaxial digital ConectorulCoaxial digital transmite semnale audio digitale comprimate. Acest tip de conexiune poate transmite date audio stereo şi multi-canal in formate diverse precum DTS, Dolby Digital etc. Este asemănător cu un cablu audio RCA comun, exceptand faptul că impedanţa sa este de 75 ohm şi că este efectuat dintr-un cablu ecranat mai gros.
Notă: O conexiune coaxială digitală nu poate transmite formate sonore de HD noi precum DTS HD, Dolby True HD etc... Optic digital ConectorulOptic digital are aceleaşi funcţionalităţi, exceptand faptul că semnalul este transmis prin fibră optică.
Notă: O conexiune optică digitală nu poate transmite formate sonore de HD noi precum DTS HD, Dolby True HD etc

[gessle]

1. What is H.264?

H.264 is an industry standard for video compression, the process of converting digital video into a format that takes up less capacity when it is stored or transmitted. Video compression (or video coding) is an essential technology for applications such as digital television, DVD-Video, mobile TV, videoconferencing and internet video streaming. Standardising video compression makes it possible for products from different manufacturers (e.g. encoders, decoders and storage media) to inter-operate. An encoder converts video into a compressed format and a decoder converts compressed video back into an uncompressed format.
Recommendation H.264: Advanced Video Coding is a document published by the international standards bodies ITU-T (International Telecommunication Union) and ISO/IEC (International Organisation for Standardisation / International Electrotechnical Commission). It defines a format (syntax) for compressed video and a method for decoding this syntax to produce a displayable video sequence. The standard document does not actually specify how to encode (compress) digital video – this is left to the manufacturer of a video encoder – but in practice the encoder is likely to mirror the steps of the decoding process. The following Figure shows the encoding and decoding processes and highlights the parts that are covered by the H.264 standard.






The H.264/AVC standard was first published in 2003. It builds on the concepts of earlier standards such as MPEG-2 and MPEG-4 Visual and offers the potential for better compression efficiency (i.e. better-quality compressed video) and greater flexibility in compressing, transmitting and storing video.
2. How does an H.264 codec work ?

An H.264 video encoder carries out prediction, transform and encoding processes to produce a compressed H.264 bitstream. An H.264 video decoder carries out the complementary processes of decoding, inverse transform and reconstruction to produce a decoded video sequence.
2.1 Encoder processes

Prediction
The encoder processes a frame of video in units of a Macroblock (16x16 displayed pixels). It forms a prediction of the macroblock based on previously-coded data, either from the current frame (intra prediction) or from other frames that have already been coded and transmitted (inter prediction). The encoder subtracts the prediction from the current macroblock to form a residual:





The prediction methods supported by H.264 are more flexible than those in previous standards, enabling accurate predictions and hence efficient video compression. Intra prediction uses 16x16 and 4x4 block sizes to predict the macroblock from surrounding, previously-coded pixels within the same frame:



Inter prediction uses a range of block sizes (from 16x16 down to 4x4) to predict pixels in the current frame from similar regions in previously-coded frames:




Transform and quantization
A block of residual samples is transformed using a 4x4 or 8x8 integer transform, an approximate form of the Discrete Cosine Transform (DCT). The transform outputs a set of coefficients, each of which is a weighting value for a standard basis pattern. When combined, the weighted basis patterns re-create the block of residual samples.




The output of the transform, a block of transform coefficients, is quantized, i.e. each coefficient is divided by an integer value. Quantization reduces the precision of the transform coefficients according to a quantization parameter (QP). Typically, the result is a block in which most or all of the coefficients are zero, with a few non-zero coefficients. Setting QP to a high value means that more coefficients are set to zero, resulting in high compression at the expense of poor decoded image quality. Setting QP to a low value means that more non-zero coefficients remain after quantization, resulting in better decoded image quality but lower compression.





Bitstream encoding
The video coding process produces a number of values that must be encoded to form the compressed bitstream. These values include:

• quantized transform coefficients
• information to enable the decoder to re-create the prediction
• information about the structure of the compressed data and the compression tools used during encoding
• information about the complete video sequence.

These values and parameters (syntax elements) are converted into binary codes using variable length coding and/or arithmetic coding. Each of these encoding methods produces an efficient, compact binary representation of the information. The encoded bitstream can then be stored and/or transmitted.

[gessle]

2.2 Decoder processes

Bitstream decoding
A video decoder receives the compressed H.264 bitstream, decodes each of the syntax elements and extracts the information described above (quantized transform coefficients, prediction information, etc). This information is then used to reverse the coding process and recreate a sequence of video images.
Rescaling and inverse transform
The quantized transform coefficients are re-scaled. Each coefficient is multiplied by an integer value to restore its original scale. An inverse transform combines the standard basis patterns, weighted by the re-scaled coefficients, to re-create each block of residual data. These blocks are combined together to form a residual macroblock.





Reconstruction
For each macroblock, the decoder forms an identical prediction to the one created by the encoder. The decoder adds the prediction to the decoded residual to reconstruct a decoded macroblock which can then be displayed as part of a video frame.




3. H.264 compressed syntax

H.264 provides a clearly-defined format or syntax for representing compressed video and related information. At the top level, an H.264 sequence consists of a series of “packets” or Network Adaptation Layer Units (NAL Units or NALUs). These can include parameter sets (containing key parameters that are used by the decoder to correctly decode the video data) and slices (coded video frames or parts of video frames). At the next level, a slice represents all or part of a coded video frame and consists of a number of coded macroblocks, each containing compressed data corresponding to a 16x16 block of displayed pixels in a video frame. A macroblock contains type information (describing the particular choice of methods used to code the macroblock), prediction information (coded motion vectors or intra prediction mode information) and coded residual data.






H.264/AVC is being adopted for an increasingly wide range of applications, including:

• High Definition DVDs (HD-DVD and Blu-Ray formats)
• High Definition TV broadcasting in Europe
• Apple products including iTunes video downloads, iPod video and MacOS
• NATO and US DoD video applications
• Mobile TV broadcasting
• Internet video
• Videoconferencing

[gessle]

What is TV Resolution?

In general, as applied to television picture quality, 'resolution' would be more accurately stated as “limiting resolution.” This references the point where individual (picture) elements are no longer discernable from adjacent elements. In other words, the TV's resolution is "limited" to how finely detailed the displayed image can be, before the elements next to each other become too blurred to be distinguishable. However, TV resolution can be described, measured and specified in different ways...

• The number of lines per (mm or inch) both vertically and horizontally.
• The number of line-pairs per (mm or inch) - vertically and horizontally.
• The number of lines per total-display - Lines per Picture Height - LPH.

The TV Picture

To understand the significance of resolution in Digital-HDTV, let's begin with the television we know - the traditional, NTSC-analog TV. It will help to take a closer look at how the images we see on the TV screen are formed.
In pictures made on film - 'movie-pictures' - images are projected on to the screen as a complete picture, in a single action. Creating video or television pictures is quite different.
The pictures and completed images we see on a traditional CRT (Cathode Ray Tube) TV screen, are really a series of horizontal and vertical lines; (visualize Horizontal Rows and Vertical Columns) with these 'rows' and 'columns' consisting of "tiny" dots or dashes.
The 'rows' are commonly called "Scan Lines" since they are applied to the screen as the 'electron gun' scans from left to right, and top to bottom. (This application of scan lines is sometimes described as 'painting' or 'drawing' the scan lines)
The 'electron gun,' located at the rear of the picture tube, is basically a wire filament that becomes heated due to resistance as electric current is applied. The heating action causes electrons to collect around the filament. By applying a high, positive voltage, the negatively charged electrons are accelerated away from the filament, and towards the phosphor-coated, interior surface of the picture tube. The accelerating electrons are concentrated in a narrow beam which strikes the coated surface of the picture tube, causing the phosphor to glow in that focused area..
Where a picture's scene is darker, the electron beam is 'weaker' - or less intense - and the phosphor 'glow' is less. Where a scene in the picture is brighter, the electron beam is more intense, and the phosphor 'glow' is brighter.
The electron beam scans across the surface of the picture tube, in direct coordination with how the original scene was scanned by the sensor in the television camera. As the scan lines vary - changing from bright, to dark, with many intensities in between - images are formed on the TV screen.
As stated above, the "resolution" of a TV is how well it is able to distinguish between the alternating light and dark lines, when these are spaced close together. If the lines are too close together (exceeding the resolution limits) they will appear merged - being neither dark, nor light, but blurred into 'muddy' shades of gray.


What All the Numbers Mean
In NTSC television, the electron beam scans (525) horizontal lines (rows) across the screen - starting with line-number (1) at the top-left of the screen, and ending at the bottom with line-number (525).
However, NOT ALL of the (525) scan lines are visible on the screen. Some loss of lines occurs while the electron beam moves from the bottom of the screen to go back to the top, and start a new scanning sequence. Also, some of the "non-visible" scan lines contain transmitting and display data - information the TV uses to create the display. Thus the total number of visible scan lines that appear on the screen is reduced to about (480 lines).
Since TV viewers are primarily concerned with just the visible scan lines, and also as a way to maintain some consistency when discussing TV resolutions, the common reference for NTSC-Analog TV resolution is 480-i; the (i) indicates that the scanning method used is "interlaced."




Vertical and Horizontal Resolution
The "vertical resolution" of NTSC TV refers to the total number of lines (rows) scanned from left to right across the screen - BUT Counted from Top to Bottom, or Vertically. This number is set by the NTSC TV 'Standard' (ie: 520 lines - 480 'visible' lines).
This Vertical Resolution number is static - it doesn't change.
Therefore, the Vertical Resolution is the same for ALL TV's manufactured to meet a specified Standard.
The "horizontal resolution," (number of vertical lines or columns) however, is variable.
The horizontal resolution of television, and other video displays, is dependent upon the quality of the video signal's source.
As an example - the horizontal resolution of VHS tape is (about) 240 lines; broadcast TV (about) 330 lines, laserdisc (about) 420 lines; and DVD (about) 480 lines.



To avoid getting entangled too deeply within the inherent complexities of TV technology, it's sufficient to note that there are a number of variables contributing to the 'stated' horizontal resolution value. Even the measurement methods are not always consistent.
For instance - how the vertical columns (dots/dashes) are counted ... as single black / white (dark and light) lines, or as "line pairs - (1) black and (1) white line."


A TV's resolution can be reported as the result of counting the total number of picture elements (pixels) per scan line, across the entire screen-width, multiplied by the total number of scan lines. However, TV screen-sizes vary, making an equal comparison of different displays more complex. TV's also differ technically, functionally and in component quality; this results in additional complications.
An alternative method is to count the number of pixels that fit within a prescribed circle, having a diameter equal to the screen height. Known as LPH - Lines per Picture Height - this is the 'correct' method in determining TV resolution.
As this shows, along with other, similar variables, the accuracy of a 'stated' horizontal resolution for a particular display, may depend on who is doing the 'stating' ...
However, for the purpose of this overview of HDTV-Resolution, the primary point regarding horizontal resolution, is that it is variable. Unlike vertical resolution which is 'fixed,' horizontal resolution can differ from one TV display to another.



SDTV and HDTV

In general, it is common practice to list a television's vertical resolution without referencing the horizontal resolution when indicating the display capability. Since the buyer is primarily interested in knowing whether or not the TV can display SDTV (Standard Definition) pictures (only), or is able to display both SDTV and HDTV picture quality, listing the vertical resolution alone is generally sufficient.
Digital TV consists of (18) specified formats accepted by the ATSC (Advanced Television Standards Committee). Of the eighteen, only those formats that apply to consumer television viewing are of interest to this present discussion. This includes SDTV (Standard Definition TV) and HDTV (High Definition Television). The vertical resolution for these formats is set by the ATSC Standard.
Note: There is an 'alternative' Digital TV Classification - "EDTV" (Enhanced Digital TV). However, since it merely denotes digital televisions that meet the SDTV Standards, and have the same attributes of 'high-end' SDTV. the value of this designation may be questionable.
The resolution set by the SDTV Standard is 480 (i/p) - visible scan lines - either (i) interlaced or (p) progressive scan.
The Standard for HDTV-Resolution is (any) one (1) of three (3) specified resolutions:
720p, 1080i and 1080p. Again, the numbers refer to visible scan lines, and interlaced or progressive scan, as applicable.


A Digital TV that is able to "DISPLAY" TV signals in HDTV-Resolution - 720p - 1080i or 1080p - is "HDTV-Capable." A Digital TV that is HDTV-Capable - AND - has an 'Internal' HDTV Receiver is called an "Integrated" HDTV. A Digital TV that can display HDTV-Resolution Pictures, but requires an 'External' HDTV Receiver is commonly referred to as an HDTV-Capable 'Monitor'.


Note: Once again, consumers are advised to use caution ...
Far too often, creative marketing and advertising practices refer to TV resolutions in ways that can be misleading. Listing a TV as, "... 'ready to receive,' 'able to process' or 'will handle' all Digital-HDTV resolutions..." does NOT offer the buyer any 'useful' information. What matters is - what resolutions will the television DISPLAY?

Different Views of SDTV and HDTV-Resolution
Digital TV - SDTV:

• 480i - 704x480 interlaced
• 480p - 704x480 progressive

Digital-HDTV:

• 720p - 1280x720 progressive
• 1080i - 1920x1080 interlaced
• 1080p - 1920x1080 progressive

More Accurate - Listing the resolution and frame rate:

• 480i - The picture is 704x480 - (60/2 interlaced frames per second)
  = 30 complete frames per second.
• 480p - The picture is 704x480 - 60 complete frames per second.
• 720p - The picture is 1280x720 - 60 complete frames per second.
• 1080i - The picture is 1920x1080 - (60/2 interlaced frames per second)
  = 30 complete frames per second.
• 1080p - The picture is 1920x1080 - 60 complete frames per second.

Comparison of Digital TV and HDTV


Note: Although "non-CRT" television sets use different technologies in creating the screen images, and there are other factors involved with how they display the picture, in the end, HDTV-Resolutions are still (720p) and (1080i) - or higher.


Because it is important, yet so often confused, it bears repeating: Vertical Resolution refers to the lines (rows) that are applied (scanned) across the screen, from left to right; these are counted from top to bottom, or vertically - thus the designation, Vertical Resolution.
Similarly, Horizontal Resolution refers to the lines (columns) going from top to bottom, which are counted across the width of the display, or horizontally - and referenced as Horizontal Resolution.

[gessle]

What Frame Rate Is
In video (both Analog and HD), just as in film, images are displayed as Frames. However, there are differences in the way the frames are displayed on a television screen. How Frames are Displayed in Analog Video
Lines and Pixels
A television or recorded video image is basically made up of scan lines or pixel rows. Unlike film, in which the whole image is projected on a screen at once, a video image is composed of lines or pixel rows displayed across a screen starting at the top of the screen and moving to bottom. These lines or pixel rows can be displayed in two ways. The first way is to split the lines into two fields in which all of the odd numbered lines or pixel rows are displayed first and then all of the even numbered lines or pixel rows are displayed next, in essence, producing a complete frame. This process is called interlacing or interlaced scan.
The second method, used in flat panel TVs and computer monitors, is referred to as progressive scan. Instead of displaying the lines in two alternate fields, progressive scan allows the lines to displayed sequentially. This means that both the odd and even numbered lines are displayed in numerical sequence. NTSC and PAL
The number of vertical lines or pixel rows dictates the capability to produce a detailed image, but there is more. It is obvious at this point that the larger the number of vertical lines or pixel rows, the more detailed the image. However, within the arena of analog video, the number of vertical lines or pixel rows is fixed within a system. The current major analog video systems are NTSC and PAL.
NTSC is based on a 525-line or pixel row, 60 fields/30 frames-per-second, at 60Hz system for transmission and display of video images. This is an interlaced system in which each frame is displayed in two fields of 262 lines or pixel rows, which is then combined to display a frame of video with 525 lines or pixel rows. NTSC is the official analog video standard in the U.S., Canada, Mexico, some parts of Central and South America, Japan, Taiwan, and Korea.
PAL is the dominant format in the World for analog television broadcasting and video display and is based on a 625 line or pixel row, 50 field/25 frames a second, 50HZ system. The signal is interlaced, like NTSC into two fields, composed of 312 lines or pixel rows each. Since there are fewer frames (25) displayed per second, sometimes you can notice a slight flicker in the image, much like the flicker seen on projected film. However, PAL offers a higher resolution image and better color stability than NTSC. Countries on the PAL system include the U.K., Germany, Spain, Portugal, Italy, China, India, most of Africa, and the Middle East. DigitalTV/HDTV and NTSC/PAL Frame Rates
Although the increased resolution capability, digital format broadcasting, and high definition video software content standards are a step up for consumers, when comparing HDTV to analog NTSC and PAL standards, the fundamental common foundation of both systems is the Frame Rate.
In terms of traditional video content, in NTSC-based countries there are 30 separate frames displayed every second (1 complete frame every 1/30th of a second), while in PAL-based countries, there are 25 separate frames displayed every second (1 complete frame displayed every 25th of a second). These frames are either displayed using the interlaced scan method or the progressive scan method.
With the implementation of the Digital TV and HDTV, the foundation of how frames are displayed still have their roots in the original NTSC and PAL analog video formats. In soon-to-be former NTSC-based countries, Digital and HDTV are implementing the 30 Frame-per-second frame rate, while soon-to-be PAL-based countries are implementing a 25 Frame-per-second Frame rate.
NTSC-Based Digital TV/HDTV Frame Rate
Using NTSC as a foundation for Digital TV or HDTV, with the frames are displayed as an interlaced image (1080i), each frame is composed of two fields, with each field displayed every 60th of a second, and a complete frame displayed every 30th of a second, using a NTSC-based 30 frame-per-second frame rate. If the frame is in the progressive scan format (720p or 1080p) it is displayed twice every 30th of a second. In both cases, a unique high definition frame is displayed every 30th of a second in former NTSC-based countries.
PAL-Based Digital TV/HDTV Frame Rate
Using PAL as a foundation for Digital TV or HDTV, with the frames are displayed as an interlaced image (1080i), each frame is composed of two fields, with each field displayed every 50th of a second, and a complete frame displayed every 25th of a second, using a PAL-based 25 frame-per-second frame rate. If the frame is in the progressive scan format (720p or 1080p) it is displayed twice every 25th of a second. In both cases, a unique high definition frame is displayed every 25th of a second in former PAL-based countries.

-interlaced scan means:that refers to a video image that is displayed on a screen by scanning or displaying each line (or row of pixels) that make up the image, in an alternate order. In other words, the image lines (or pixel rows) are scanned down the screen from top to bottom, in an alternate order (lines or rows 1,3,5, etc... followed by lines or rows 2,4,6). The entire image is displayed every 30th of a second.

-progressive scan means that is a system in which the image is displayed on a screen by scanning each line (or row of pixels) in a sequential order rather than an alternate order, as is done with interlaced scan. In other words, in progressive scan, the image lines (or pixel rows) are scanned in numerical order (1,2,3) down the screen from top to bottom, instead of in an alternate order (lines or rows 1,3,5, etc... followed by lines or rows 2,4,6). By progressively scanning the image onto a screen every 60th of a second rather than "interlacing" alternate lines every 30th of a second, a smoother, more detailed, image can be produced on the screen that is perfectly suited for viewing fine details, such as text, and is also less susceptible to interlace flicker.

[gessle]

How HDMI Works


Before the development of high-definition televisions, most TVs displayed pictures in what is now known as standard definition. The picture was roughly square -- its aspect ratio was 4:3. Its resolution, or the number of dots that make up the picture on the screen, was about 704 x 480 pixels. The picture was interlaced -- each piece of the moving image was really half a picture, but the pictures changed quickly enough that the human brain didn't really notice. Finally, older TVs relied on analog signals, which travel as a constantly varying electrical current.
HDTVs, on the other hand, are digital. They use information in the form of ones and zeros. This information travels through cables as distinct electrical pulses. HDTVs have an aspect ratio of 16:9, so the picture is rectangular. They also have a higher resolution -- current HDTV standards allow for resolutions of up to 1920 x 1080 pixels. HDTV signals can also be progressive, meaning that the each frame of the moving image is a whole picture rather than half of one.

So, compared to standard TVs, HDTVs have a wider screen, more pixels and a faster refresh rate. Often, HDTVs can display more colors than older sets. This means that HDTVs need more data and need it a lot faster than standard-definition TVs do. If an HDTV can receive this information digitally, it also doesn't have to spend time or processing power converting the signal from an analog format.This leads us to HDMI. Created by a group of electronics manufacturers, the HDMI standard is a set of guidelines for creating high-bandwidth connections between digital devices. With the right setup, HDMI can make a significant difference in a home-theater system. The current standard can carry 1080p high-definition signals, and it supports eight channels of uncompressed audio, enough for a 7.1 surround-sound system.HDMI can cut down on the number of cables required to connect components, and it can even reduce the number of
remote-controls needed to watch a movie.

But there's a catch. In order to take advantage of everything HDMI has to offer, all of the components of a home theater have to be compatible with them. Some of the features HDMI touts also don't yet exist in the consumer marketplace. In addition, there's a limit to how long an HDMI cable can be, and some users complain that the limit is too short to support convenient setups. Here, we'll look at exactly what happens inside an HDMI cable, the standard's features and its pitfalls. We'll also examine whether the newest standard, HDMI 1.3, really renders the earlier standards -- which have been out for only a few years -- completely obsolete.

HDMI Signals

One of the common misperceptions about HDMI is that the digital signal is innately superior to an analog signal. In some people's minds, the lack of
analog-to-digital conversion means that the signal is in a pure, undamaged state when it reaches the HDTV set. It's easy to imagine a high-definition, digital signal traveling straight from an HD-DVD player to an HDTV. But signal transmission via HDTV does require an encoding step. HDMI uses transition minimized differential signaling (TMDS) to move information from one place to another. TMDS is a way of encoding the signal to protect it from degrading as it travels down the length of the cable. Here's what happens:
The sending device, such as an HD-DVD

• player, encodes the signal to reduce the number of transitions between one (on) and zero (off). Think of each transition as a sharp drop-off -- as the signal travels, this drop-off can begin to wear away, degrading the signal. The encoding step helps protect signal quality by reducing the number of chances for the signal to degrade.
• One of the cables in the twisted pair carries the signal itself. The other carries an inverse copy of the signal.
• The receiving device, such as an HDTV decodes the signal. It measures the differential, or the difference between the signal and its inverse. It uses this information to compensate for any loss of signal along the way.

HDMI also has the ability to protect data from piracy. It uses high-bandwidth digital copy protection (HDCP) to accomplish this. HDCP is an authentication protocol. Basically, each home-theater device has identification data and encryption data stored on its extended display identification data (EDID) chip. The source device, such as a Blu-ray player checks the authentication key of the receiving device, such as an HDTV. If both keys check out, the sending device moves on to the next step. It generates a new key and shares it with the receiving device. In other words, it creates a shared secret. Ideally, this whole process, known as a handshake, takes place almost instantaneously.

The source device encodes its information using the key it generated it. The receiving device decodes it using the same information. If an unauthorized device tries to intercept the data, the source device stops transmitting. It also makes sure that the key hasn't changed and that the system is still secure every few minutes. All HDMI-compatible devices are required to support HDCP, but the companies that manufacture and distribute high-definition content aren't required to enable it. In the United States, this content-protection ability is mandated by the Federal Communications Commission (FCC).
Next, we'll take a look at the HDMI connector and cable and explore how they carry high-definition signals.


HDMI Connections


So we have:

• Component video carries analog video signals separated into two channels for color and a third for luminance. Component video cables use RCA connectors.
• S-video transmits analog signals using one cable and a four-pin connector.
• DVI, or digital visual interface, is a 29-pin connection commonly used with computer monitors. Unlike composite video and s-video, it carries digital signals.

Many HDTV early adopters rely on DVI, since it hit the market before HDMI did. Since DVI and HDMI both use the TMDS protocol, they're compatible. All you need to connect an HDMI cable to a DVI port is a passive adapter.

The DVI and HDMI connectors have some other similarities. Both use a grid of pins to transmit signals from the cable to the device. While DVI has a 29-pin connector, HDMI's type A connector has 19 pins. A DVI connector also uses a pair of built-in screws to anchor it to the device. HDMI plugs don't have this extra support, and some users have expressed concern that this puts unnecessary strain on the device's circuitry. There's also a miniature version of the HDMI connector for use on smaller devices like digital camcorders as well as a 29-pin type B connector, although most consumer devices use type A. From the HDMI connector's pins, signals travel through twisted pairs of copper cable. Three audio and video channels travel through two pins each, for a total of six pins. The TMDS clock, which allows devices to synchronize the incoming data, travels through one pair of pins. Each of these four total pairs has a shield -- another wire that protects it from interference from its neighbors. The TMDS channels, the clock and the shields make up the bulk of the cable pairs inside the HDMI cable.

he other signals that travel through the HDMI cable need only one pin. One such channel is the consumer electronics channel (CEC). If your devices support it, this channel allows them to send instructions to one another. For example, an HD-DVD player could automatically turn on a home-theater receiver and an HDTV when it started playing a disk. The hot plug detect channel, which uses one pin, senses when you plug in or unplug a device, re-initializing the HDMI link if necessary. The one-pin display data channel (DDC) carries device information and the HDCP encryption information discussed in the previous section. Other channels carry encryption data and electricity to power communication between devices.

The cables themselves come in two categories. Category 1 has a speed of 74.25 MHz. Category 2 has a speeded of 340 MHz. Most consumer cables are the faster category 2 variety.
In addition to the connector and cable, the HDMI standard applies to how TV sets can synchronize sound with video and display color. These capabilities have changed significantly over several revisions to the standard, which we'll compare in the next section.

HDMI Standards and Revisions

The first consumer products with HDMI connections hit the market in 2003. Since then, there have been several changes to the HDMI standard. For the most part, these standards have added support for specific types of content or applications. For example, the first revision, HDMI 1.1, added support for dvd audio
The most recent major revision -- the jump from version 1.2 to 1.3 -- got a lot of attention. New features included a massive increase in bandwidth, support for 16-bit color and support for the xvYCC color standard, which supports additional colors. A new lip-synch feature also reduced that sound and video would fall out of synchronization during playback, making an otherwise immaculate recording look badly-dubbed. Some reports even claimed that any devices that did not have HDMI 1.3 were obsolete.

In some ways, this was just as confusing as it was impressive. Some of HDMI's new abilities don't exist yet in the consumer marketplace. For example, the increased bandwidth -- from 4.9 Gbps to 10.2 Gbps -- can support a refresh rate of 120 Hz, or 120 frames per second. This is twice as fast as the maximum refresh rate in the current HDTV standard. HDMI 1.3 can support 30-, 36- and 48-bit color options known as deep color, but many media players and recorded video materials don't go beyond 16-bit color. Critics also claim that deep color allows HDTV screens to display colors that most people can't even perceive. In addition, while lip synch and one-touch control abilities can be handy, not all HOME THEATER
devices support them. Fortunately, a lack of 1.3 capability doesn't mean your HDTV is useless. HDMI 1.3 is backwards compatible with previous versions. It's like when color TV debuted. People could watch color TV signals on their black-and-white sets -- the TV still worked, but the picture was still in black and white. If your HDTV has HDMI 1.2 but your new components have HDMI 1.3 capabilities, your TV will still work, but without the expanded 1.3 abilities. Since the bandwidth allotments of previous standards are generally enough for most high-definition applications, your picture should still have a pretty good quality.

Another common concern about HDMI is cable length. Although the HDMI standard requires a minimum operable length of 32 feet (10 meters), some users report significantly shorter operable lengths in practice. This is particularly true when transmitting 1080p signals -- the increased demands on bandwidth speeds up the deterioration of the signal. Fortunately, there are amplifiers and extenders that can decode, re-set and re-encode the signal before sending it on the next leg of its journey. For people who are concerned about HDMI's potential limitations, there may be another solution on the horizon. DisplayPort is a new high-definition standard that will cover connections inside devices, like within a laptop, and between devices, like from a media player to an HDTV. DisplayPort hasn't hit the market, though, so whether its quality will surpass that of HDTV is still to be determined.

[vasile101]

Informatiile despre HDMI sunt foarte interesante si pertinente, ca si tot acest thread. Multumesc pe aceasta cale @gessle.
Pentru @gessle sau cine e in masura sa ne lamureasca, exista un standard 1080p (1920x1080) la 23.976 fps pe HDMI ? Daca da, un televizor LCD, de exemplu, cu interfata HDMI ar trebui sa-l recunoasca si sa-l afiseze ca atare sau il va incadra la 24fps ? In unele documentatii tehnice am vazut 23.98 fps, dar de fapt valaoarea exacta a frame rate-ului este de 23.976. Unul din motivele pentru care intreb acest lucru este faptul ca, aparent, un handshake pe HDMI intre WD TV si un TV LCD de la LG la 1080p 23.976 fps nu s-a incheiat cu succes, in schimb 1080p 24 fps a mers.
Cred ca tot ce este film HD din State vine pe disc cu informatie la acest frame rate si banuiesc ca la acest frame rate este si redat de un player BD.
Ca sa fie pomana completa, niste link-uri catre informatii de standard HDMI ar putea sa ne dea cineva?
Cu multumiri,

vasile101