Home cinema

The home theater (of English: Home Cinema) is used for acoustic and visual replication of the cinematic experience in private homes. Here the claim grows on the quality of the development of the cinema on the one hand ( Raumtonverfahren ) and with the development of the technical possibilities of entertainment electronics on the other.

History

Already in the 1930s there were narrow films the company AGFA that could be created with specially designed cameras and presented with projectors at home in silence. Also, there was at that time already buying movies, so already professionally created films that were copied in large numbers and bought in stores.

In the 1960s, the Super8 cine film format was introduced by Kodak. Then began a veritable boom of home theater. Several Hollywood studios opened archives to distribute movies as Super8 versions. Thus, films of the Disney Group under the name were sold " Disney Home Movies " in Germany. The cine-film boom ended in 1982 after the introduction of the Video Home System (VHS), the production of cine films there but until today.

In the 1960s, a simple TV has been viewed as a home cinema (or the goggle-box ); devices used today, however, are about Blu- ray Disc players, Dolby Digital / DTS sound systems as well as high-quality, large-format televisions and projectors.

Typical structure and components

The term home theater includes a true cinema experience at home and thus a demand for high-quality entertainment devices. A typical home theater includes:

In some cases, the room is also completely rebuilt and modeled after a real cinema. It is not only paid attention to the proper selection of the cinema seat, but also to the appropriate room setup with separate chamber for the equipment to reduce noise, dimmable light, and even set up for the popcorn machine everything in detail. Modern cinemas also have a system automation that can be automated by pressing a variety of programmed scenarios.

Lately, more and more home theater with home theater PCs, called HTPCs are equipped. These versatile systems can be easily integrated into the existing home theater. These special PCs are easy to customize the required expectations and with the correct configuration picture and sound qualities can be achieved with which the measure is of high quality equipment at a comparable price, not only, but they can also excel. This multi-media PC can be operated either with normal operating systems such as Windows, Linux or similar, or with specially developed software packages such as Windows Media Center Edition, MediaPortal or VDR. Some manufacturers have specialized in the construction of such machines and one finds increasingly provider.

Generally, there are, as in the past in the hi-fi scene, often violent and controversial discussions about the quality and usefulness of individual home theater components.

Surround sound systems

Over time, the Kinotonstandard developed into an enveloping sound experience with the audience many soundtracks, which also from back to front wandering sound effects or realistic ambient noise, for example. In the home theater, the development of mono went (one audio channel ) and stereo (collectively the " space " in the home usually two channels) to Dolby Surround or Dolby Surround Pro Logic. This is a four-channel remix of a stereo signal, in which an inaudible without a decoder rear effect channel was mixed, also can be generated from the two front channels, a center lying between these signal.

Initially offered mainly hi-fi stereo VCR and the less common laserdisc the possibility of an improved sound. ( Transferred independently) With the introduction of the DVD in 1997 with Dolby Digital and DTS for the first time with a maximum of six discrete channels plus a subwoofer channel ( LFE) for bass effects arose again an improvement of technological possibilities. Dolby Digital was first used since 1992 in the cinema and on laser discs until it found widespread use with the DVD-Video. It can only be transmitted over digital signal paths. A similar variant thereof are the Dolby Pro Logic II and Dolby Pro Logic IIx, which can provide a similarly good quality delivery path in two analog audio channels. A newer version of Dolby Digital Dolby Digital Plus.

This means the purchase of a special home theater receiver (AV receiver ), which forwards the digital multi-channel signals separately to the different speakers in the home theater. Typical systems consist of three speakers in front ( "Front", on the left, center, right) and two at the back on the sides ( surround left and right), which are often slightly higher ( THX standard about 60 to 100 cm above ear level ) and after inside are placed shot ( with movies, it is recommended to leave the boxes emit diffuse, not directly at the viewer ); as well as the subwoofer. Is there a subwoofer, so a reversal of the LFE channel to the front speakers is possible, even the center channel can be distributed to them. In some systems (6.1) there is also a rear center speakers (Surround Back) at 7.1 systems even two.

Surround sound simulation systems such as Virtual Dolby Surround, which will also allow two-speaker surround sound, often do not reach the quality or sonority real surround sound systems. Relatively good systems are here Dolby Virtual Speaker and Dolby Headphone.

Multichannel audio systems are compatible by a downmix well to two-channel stereo. Conversely, an upmix to Dolby Digital 5.1 or other systems is carried out with some older films.

Due to the boom in flat-screen televisions are marketed from amplifiers, speakers and built-in DVD or BluRay player on the market as a home theater system affordable complete packages consisting now.

Projectors

For a really large image projector, home cinema is almost always digital, large movie theater still mostly analog, first prerequisite. In the early days of laser disc beginning of the 1980s, only a very small number of film enthusiasts could afford the then available very expensive CRT projectors. With the advent of digital projection in the 1990s began a process of price decline, still persists today. Thus there are (as of 2012) as early as about 800 € high-resolution projectors (1920 x 1080 pixels) that come up in the home theater with the appropriate high-definition source material (Blu- Ray, etc. ) to the image quality of current cinema halls almost. Most home theater projectors use lamps from 130 to 180 watts of power. Herewith are (depending on personal taste) image widths of 200 to 300 cm. In the "high-end " class, there are also much stronger projectors up to 700 watts of light output, thus to realize image widths beyond 400 cm.

The brightest digital projectors eventually be used for lamp powers up to 2 x 2000 watts already in commercial cinemas, which screen widths for up to 20 meters.

Projection

Although the term "canvas" is still common, such as linen are commonly used today materials such as plastics or glass fibers for fabrics instead. Both retractable screens (some with motor) as well as fixed mounted screens are common, where the former may tend to form waves. Most pure white is common, some are of the view that a lighter shade of gray gives the best results. A characteristic of a screen is the luminance factor, which describes the brightness depending on viewing angle. Too high a luminance factor or an unsuitable material can lead to the formation of hot spots, so an overly bright image area, disrupts the visual impression.

Typical image widths in the home theater area are located in a region around the two meters, usually well over one, but usually less than three, as results from the performance of the projectors is a limit. The format is usually 16:9 usual, which is used in part with sliding black masks for other image formats.

In addition to ready to buy canvases and DIY solutions are very widespread, be quite creative part and allow accurate adjustment to the personal circumstances and preferences. Major components are as plastic films, which are clamped together with opaque black fabric as a background on a frame. Other solutions are based on some chipboard or MDF boards with emulsion paint, plastic coating or spanned films. A common type is a black outline of a few centimeters wide, which is to improve the contrast.

The most annoying artifacts in practice arise with canvases by contamination of parts of the screen. Very slight wave formation, however, usually falls on significantly less. Also the price of a canvas is far less important as long as these free of debris, a halfway reasonable luminance factor was selected and the wave form holds (for roller - screens ) within limits. The best screens are monochromatic room walls, possibly smoothed and painted with special paint, they are hardly the frame screens after. In general, the surface should be rather dull and less shiny, otherwise can form hot spots.

Quality of image sources

For large-scale projection canvas suitable sources

The large viewing angles, as they are necessary in the cinema or home theater, is the quality of the source material is of decisive importance. Qualitatively really high-quality moving images for home are far possible if you called in Europe is not widely used laser disc, optical disc also, once apart. The color reproduction, freedom from noise and resolution of the various video formats have always been less than professional standards, that is no really good large projection was possible.

The modest picture changed with the introduction of digital television and the DVD ( from 1996). The best format but (since 1992, since 1999, for example used in the United States to a greater degree ) high-definition television HDTV with up to five times the DVD resolution, which can be seen since January 1, 2004 in Europe via Astra. In addition to the high resolution, there is a better HDTV color representation and almost total lack of compression artifacts. Both are criticisms that stand in uncomfortable fact for DVD material and a great home theater.

Must distinguish, in practice, between large format displays (currently mostly to 50 inches (127 cm ), partly to about 65 inches - 165 cm diagonal) screen and projection. With an affordable HDTV home theater projector around 1000-2000 Euro, which is often even lower than current large-format flat panel, screen widths of 250 cm can be achieved effortlessly. With the usual viewing distances in the range of three to four meters of the viewing angle is now so great that the resolution of the European PAL signal ( DVD, digital TV ) and can not be sufficient for a satisfactory image.

However, if an experience is generated as in the cinema, this inevitably leads to a big screen in combination with a projector. Frequently encountered viewing distances are often in the range of about 1.5 times ( sometimes up to a factor close to 1 down, maximum 2 ) image width, integrated view angle in the range of about 30 to 35 degrees (some even more).

For such purposes, a small hobby as well as Camcorder with artifacts occupied analog television is of VHS video, limited to not suitable. Very good PAL signals, as offered by some of DVDs or 16:9 broadcasts a high bit rate of a few TV stations in the digital television ( this is known as the ZDF) rich in many scenes already, but let but for scenes in the miss shots sharpness. This HDTV is now considered indispensable, at least if a comparable to a really good 35 -millimeter copy impression to be created. Even with a HDTV-capable projector and good scaling (about to 720p in the current models, possibly with an external scaler ) An improvement is possible. In addition to a DVD player and digital satellite receivers and home theater PC, HDV camcorders, HD - DVD and Blu- Ray devices are well suited.

If we understand by " home theater " but also installations with significantly smaller viewing angles ( about 10 ° ), as in the different variants of the flat screens with display widths of usually less than one meter, it shall be sufficient in this case, the playback via DVD or digital TV with good PAL signal usually still easily made .

35 -millimeter movie compared to home theater

In theory, depending on the program content, 35 -millimeter film a HDTV projection of a well-balanced home theater still be superior, in practice, however, it happens again and again that the film copies shown in cinemas seem worse than HD video from Blu - ray disc.

In movie theaters comes with the 35 - millimeter film, a film format is used, which was developed in the 1890s, the end of the 1920s was also used for use as a photographic film, but there horizontal double image size.

Of the original film reels of recording cameras is usually from several hundred individual "takes", a primal version cut together (usually without sound, but already with all digital effects). This is (English: answer print) as a template for the so-called " zero- copy ", a light- corrected film copy of the entire work with Dialogton including music and sound effects. This first copy of the film is used to test screening with producer, director, and optionally a test audience in Germany and forms the basis for the related right under Section 94 of the Copyright Law. Of this is a re- light a corrected " correction copy " customized, that is used as a basis for further positive. These are then projected in theaters using analog technology to the screen, and depending on the care of the copying work and depending on care when handling the copy quality can vary considerably.

This procedure was formerly (until the 1980s ) purely analog, it was so worked exclusively with scissors and Filmkitt or tape. Today, most of the films for cutting all rolls of film are digitally sampled and stored in a computer system. Only here, subsequent steps, such as color and brightness corrections or digital effects added. The present (2006 ) efficient method called " digital intermediate " and is used in almost every major productions. The best image quality is now so in digital form on a disk cluster with some well over 100 terabytes available as a digital master. Unfortunately, the transmission comes in a 35 -millimeter form for the release prints via laser engine for cost reasons only for the master tape in question. Only this master tape and a few other "Premiere copies " also carry almost the full image quality. From now on, when other analog copying, the image quality from the time, such as the popular Hollywood productions are often on 35 -millimeter film prints to theaters, which are already at fourth or fifth generation.

As is usually lost by the method of distributing a lot of image sharpness and color brilliance, the 35 -millimeter format in the cinema can deliver its maximum possible quality in contemporary practice actually never. Due to the small area of film sufficient reserves are often available for the necessary duplication in the Quick Copy streets. This is the main reason for the often much better overall impression of digital HDTV projection, whether in the movie theater with digital projection or at home. A similar impression to better produce only remembered not for the mass market premiere copies.

This is also the reason why a 16mm blow-up, ie the copying of 16 - millimeter film (or even DV ) to 35 -millimeter movie copies does not necessarily stand out negatively.

The fact that the image quality is significantly better at IMAX versions, is due to the larger film format (a special 70 - mm format) as well as the quality.

Since most films are edited digitally, some are already being recorded digitally, already data are available. The transfer to 35 - millimeter film is done only in order to be compatible with the existing in cinemas traditional technique.

For film distributors, it brings a substantial relief to distribute films digitally, the image impression can be better in practice, in larger cinemas but it can happen depending on the resolution of the source material and beamer that digital projection negative attention by artifacts (pixels stairs).

At the moment, the digital distribution via hard drives that consume significantly less space than film roles takes place. Later, a transfer via data cable or satellite is conceivable.

For home cinema use the movies on Blu -ray discs are supplied, which have a much lower capacity than intended for cinema use hard drives. So that only much lower data rates are possible, but still are significantly better than in the DVD.

The movie experience in the home theater can in principle be more attractive than a movie theater, in which a number of factors can spoil the movie experience in which the viewer has no control. If one disregards the factors that have to do with the presence of other viewers and would be given, in principle, theater visits, too much residual light remain principally by unfavorable placed emergency exit signs and factors associated with the quality of the playback system and / or the have to do source program as too dark projection, lack of focus, poor sound, and depending on the method used, picture shaking ( analog) or system crashes ( digital). In addition there are in digital cinema projection problems that have to do with digital rights management and can lead to a demonstration of the system will stop partway through.

This results in respect of an image reproduction in the cinema the following properties, which depend partly on the recording on film, some of the properties of the film print in the cinema and the cinema projector:

A resolution of " 2K", or about 2 million pixels
An " isotropic " image appearance, without a preferred direction, due to the disordered structure of the film grains
A caused by the filming rate of 24 frames per second
A playback rate at the cinema projector 48 images (sometimes 72) per second because each image is displayed twice with a short interruption
A film- specific color space, the recording material used and the addition of coloring in post-production depends
A specific appearance of surfaces due to the granularity of individual images which are shown in chronological order in a row.
A specific behavior when ( highlight ) and underexposure
An in -image contrast of about 1000:1 ( ie about ten stops extent ). that is, the brightest displayable digits of a given, the currently displayed image can about 1000x let as much light falling on the screen as the displayable darkest.
Temporal and spatial convergence of the image information, ie on a single frame of the movie to find all the color information for this image at locations that were also available in the recorded subject, and which are projected simultaneously onto the screen.

For a theater - like effect at home it makes sense to aim for a reproduction that is as close as possible to the above specifications. However, many home theater users also see improved ways of using video projectors and prefer partially achievable through video projectors image effect.

None of the video projector technology currently widely deployed allows full film proper playback. In particular:

A resolution in the range of 2K is practically achievable with many video projectors available today, as 1080p is just a little under 2K.
An isotropic play is already no longer possible, since all technologies (except CRT monitors ) function with fixed, square pixels. Between these are visible in the projection distances, leading to a fly screen effect. This is more or less serious depending on the technology used. When the LCD, there are more structures in Digital Light Processing these are less pronounced and weakest in LCoS. To reduce the lattice structure, so-called "Smooth Screens" (a kind of optical filter in the projector optical path) be used.
The recording frequency of 24 images per second, in combination with the usual exposure time of movie cameras of about 1/48 second to a specific film - typical movement pattern. Since the Blu -ray Disc standard digitization in this frequency ( " 1080p/24 ) allowed by HDMI cable and a corresponding transfer from the player to the video projector is possible to request a 24p playback should be regarded as fulfilled, although many Blu -ray discs are not encoded accordingly.
The situation is different on the player page. Many video projectors use a playback frequency of 60 or 120 Hz Relative to 24p film sequences, this means that each film frame five times (instead of at the cinema two or three times ) would have to be repeated to compensate for the differences. Various methods are used to effect an adjustment, in addition to the movie similar, repeating, or so-called pull-down and frame insertion method. These are briefly described in the article to 24p. To complicate the situation, if the footage is not sent as 24p image sequence to the projector, but as a so-called field sequence (see interlacing). Here the projector to detect attempts to whether the footage originally interlaced was already ( has been so taken by a classic video camera ), or original frame (progressive ) was and has only broken from the playback unit before transmission to the video projector into fields. In both cases, the video projector in front of the display fields is again to frames together, but in the case of a cut in half pictures frame simply " deinterlaced " are the rows of the (hopefully correctly assigned ) fields, but possibly worked in the case of the original fields with intermediate images is to computationally compensate for the time lag in which the two fields have been added. How well it succeeds depends exactly as in the case of frame insertion of the methods used, manufacturer - specific from.
The color space of film deviates already from physical reasons, the color space, which can produce the electronic devices. In addition, color spaces are used in home cinema for reasons of historical compatibility, which originate from the field of classical television technology and that are adapted to the capabilities of CRT TVs for color reproduction. In particular be mentioned here are the ITU -R BT 601 color space for SDTV material and the BT.709 color space for HDTV material. Today's home theater projectors could represent a larger color space in many cases; However, it fails to appropriate standards. Only the xvYCC color space of a few projectors ( and many flat screen televisions ) support; However, neither television programs are broadcast with this color space, nor is it provided in the Blu -ray Disc standard. Only some video cameras with AVCHD offer the ability to record with this color space. The Digital Cinema Initiative "Digital Cinema Initiatives " has therefore defined as the entire color space CIE color space, even if today's cinema projectors that can not display. For color space also includes the fineness of the gradation in the presentation of colors and shades of gray. With the usual 8 bits, a maximum of 256 color levels ( de facto, but in BT 601 and 709, only the values from 16 to 235 uses ) for each base color and black and white films basically only 256 gray levels, which can lead to visible gradations in the image. Some projectors gradually the image from fine ( also referred to as " Deep Colour " ), which is achieved by interpolation of the image information. This can be thought of as that in example 10 bits are the gradation values are no longer 16, 17, 18 .. 235, but 16, 16.25, 16.5, 16.75, 17, 17.25 ... 234.75, 235
The image perceived by the rapid Hinte clean mess projection of grainy images is the home cinema also not be simulated. Video projectors have their own noise, which, however, differs from that of a film grain. To view DLP projectors in darker, but partly also in brighter areas of the image color noise by problems in the control of individual mirrors. LCoS projectors can blur the image in places due to the inertia of the LCD switching, but rather leads to a smoothing as to noise, etc.
Also, the epitome contrast of footage is not accessible from today's video projectors. A measurement method that measures this Inbildkontrast in projectors, has been defined by the ANSI. Here's a still image is displayed with a checkerboard pattern of 16 maximum white and black squares maximum ( projected ) and the brightness of all fields is determined. The so-called ANSI contrast is then obtained from the ratio of the average brightness of the white fields to the average brightness of the black boxes. For DLP projectors are a manufacturer to values of about 350:1 to 800:1, with LCoS projectors, the amounts are from about 300:1 to 420:1, depending on the measurement differently. Projector manufacturers attempt partially to mitigate these limitations in contrast by projectors with a so-called dynamic iris are provided, which can change the overall image brightness by automatically switching between high and low beam. However, this does not improve the contrast within an image and can cause the image brighter or darker in the parts through the readjustment, which actually is a result of specific changes in scene brightness (eg when panning or the disabling of a lamp) have not changed, which can lead to an unnatural impression. (Note: the values given by the manufacturers usually refer not to the ANSI contrast, but the on / off contrast (on / off, native, static, etc. ), in which successively a white image and a black be projected image and measured, or the dynamic contrast at which the white image is projected additionally in maximum open position and the black iris with maximum iris stopped down ).
The temporal and spatial convergence of the image information in a single image with current video devices also not 1:1 simulated. Apart from the fundamental, above mentioned problems dubbing of temporally successive half images recorded in many sources, the video projectors can only annhähern this convergence for technical reasons. In LCoS and 3LCD projectors are means of three micro - LCD panels, which are each irradiated with light of different wavelengths (red, green and blue) produces three separate images for the three primary colors, then with the help of mirrors and prisms in a common beam path to be merged. There may be variations due to manufacturing tolerances, so that the three images on the screen does not exactly coincide (lack of vergence ). It thus lacks the spatial convergence (some projectors allow a digital balance, in which the image of each color can be pixel increments. Vergence of less than half a pixel are thus but the principle, not correctable, and tilts relative to the optical axis without this not at all). In DLP projectors with a single micromirror array (so-called 1-chip DLPs ) the three images for the primary colors are generated sequentially. Although they are always exactly over each other due to the use of a single mirror, but the color impression arises only by the inertia of the observer's eye that perceives the three successively projected monochromatic color images as a single. It lacks the temporal convergence. In rapid eye movements are the individual color images, which then meet at different locations on the retina, perceived by many observers as color flashes, which is called a rainbow effect and can distort the impression especially with black and white films.

5.1 surround sound Low-frequency effects Composite Video S-Video Video Disk Recorder Downmixing 4K (resolution) High Definition Television Vergence (optics)

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