Appeared in July 2005. The recommendations of the group of production companies OS! strictly regulate the quality of the screen image in digital cinema. During the discussion of this document expressed the view overestimation of requirements and possibilities of their application. This was said to the projection of relatively simple and low-cost video projectors with the characteristics of the screen image, essentially conceding the relevant recommendations of the OS !. This article analyzes the parameters of a moving picture based on the concept of the «ideal» and moving picture shows the validity of the recommendations of the operating system !. The article also provides an analysis of the environmental performance of a digital moving picture and provides some information on the history of development of domestic electronic cinema.
1. The concept of the resolution of the ‘ideal’ digital moving picture.
In modern systems, visual information display field of view of the screen is a different amount depending on the type of system.
Modern cinemas angle at which the viewer is watching the screen image is 70 degrees (or more), and in some cinematic systems (1MAH) field of view can reach or exceed 180 degrees.
Considering that the resolution of the average human visual analyzer under observation cinematic image is of the 2 ‘(two angular minutes), then the average angle of the field of view of 70 degrees to the screen resolution required for horizontal screen image should be:
70 x 30 = 2100 elements (for «ideal» system display t. E. For a system that is optimally matched to the characteristics of human visual analyzer).
In accordance with the Nyquist criterion (or Nyquist’s theorem) for undistorted transmission 2100 pixel is required 2100 x 2 = 4200 counts, or bins. Thus, the number of bins (pixels) in a digital display system «ideal» cinematic system with an angle of 70 degrees the field of view of the screen is 4200 pixels.
2. Resolution of real cinematic systems.
In real systems 35 mm film projection film screen resolution images, in accordance with national and international research is not more than 1.5 K = 1536 pixels.
The DCI specification for digital cinema, there are two quality options screen image:
Option 1: The quality of the screen image should be no worse than the 35mm film projection systems.
Option 2: the quality of the screen image must exceed the corresponding figure of 35 mm film projection systems.
In accordance with the foregoing, the first version of the digital cinema resolution of the screen image should be at least
1.5 K = 1536 pixels. Selected for this option resolution is 2 K = 2048 pixels., Which is somewhat larger than the corresponding value at 35 mm film screenings.
For the second option recommended the resolution of the horizontal screen image is 4 K = 4096piks. Such permission is almost consistent with the requirement for an «ideal» system (4200 pixels. When the field of view of 70 °) and a significantly higher resolution than 35mm cinema film system.
3. Features of digital content and compatibility DCI DCI formats and other formats.
To implement a system of electronic digital cinema 2 K and 4 K requires relevant content. In accordance with the recommendations 0S1 such content than the content portion must have certain metadata involving only play content using a projection apparatus, meeting the requirements 0S1.
Trying to use in the electronic cinema digital projector with features that do not comply 0S1, will lead to the inability of the projection of the corresponding content, t. E. There is a fundamental incompatibility between these projectors content 2K and 4K 0S1. The reasons for such incompatibility as follows:
— To receive and process signals 0S1 digital projectors with a resolution of 2K or 4K media equipped with a special unit that produces a digital stream decoding 0S1 and converts it into a form suitable for a digital projector. The media unit is part of DCI and the projector can not work with other types of projectors.
— Interfaces projectors that do not meet the requirements of 0S1, do not recognize the signals 2K and 4K on the grounds of resolution, depth of quantization signals of primary colors and other parameters. These projectors also have the ability to ensure correct color reproduction when playing film content and control color correction in cinema.
— Digital projectors with a resolution of about 1K can not transmit 14 — bit quantization of the luminance signal. They are only designed for 8-bit quantization of signals of primary colors, which corresponds to the quantization of a digital television signal.
Thus, a forward and backward incompatibility content 2 K and 4 K with a simple and cheap projectors, as evidenced by such passport data projectors.
The use of special buck converters (like converters BpeP&MNsoh) theoretically allows content projection 2 K and 4 K through projectors 1K. However, the image quality deteriorates significantly, and in some cases may become unacceptable due to occurrence of such errors as «moire».
Cost down converter Snell&Wilcox significantly exceeds the cost of projectors 1K.
Even the theoretical possibility of converting the content in 2K and 4K content 1K can not be realized due to the existing content in 2K and 4K 0S1 multi-stage protection against tampering and playback.
Consider some of the levels of content protection DCI.
1 The effect of «mix» — the fragmentation of the image frame and mixing fragments according to the law of random numbers from frame to frame. To restore the normal image needs applied code of random numbers, this is the «key». The key is purchased with the acquisition of content.
2 Protection against unauthorized interference in a substantial part of the content. When you try to intervention (or attempt to transform the content K 1 K, which is similar to the intervention in the content part) access to the content permanently blocked. It provides copyright protection and prevents unauthorized changes of the content. There is no «key» to provide access to a substantial part of the content is not there, the so-called. «Deaf defense.»
3 Introduction to the content of special «watermarks».
When you try to retake the video camera from the screen during the demonstration content OS! peresnyatom in the video signal will be present special introduction marks the ownership of the content and unauthorized playback. This information is sufficient for filing a lawsuit for copyright infringement.
Note that for Russia’s WTO accession will be specially adopted very serious law on criminal liability for copyright infringement.
4 digital projection movie
In accordance with the recommendations of the document Digital Cinema System Specification v.1.0 July 20, 2005, an image on a screen must meet the following requirements.
5 Existing systems E-cinema in Europe and Asia
Over the past 10 years in Europe and some Asian countries to build systems E-cinema, which provide on-screen image quality corresponding to the SDTV (standard conventional TV). Considering that the resolution of SDTV system is about 500 e horizontally for undistorted transmission of the image when you want to digitize approximately 1,000 samples, which corresponds to 1K resolution (1024 pixels).
Some of E-cinema systems in Europe provide imaging standards 720P (1280 x 720 pixels). The development of such systems is associated with the spread of satellite TV broadcast relevant content. The quality of the screen image corresponds to the TV standard HDTV (high definition television) and inferior image quality in a 35mm film projection.
China. Until 2005, China introduced several halls of electronic digital cinema in HD 720P. (1280 x 720). In 2006, it acquired 43 video projector 720p and 47 video projectors 2K DCI. In 2007, the planned purchase of 100 video projectors 2K DCI. Therefore, the Chinese film industry since 2007 completely converted to a digital display, in accordance with the specification of 2K DCI.
India. According to the Minister of Culture of India in 2006 for India IBC- unacceptable option DCI because of its high cost. Currently, India has a system of digital satellite cinema with 720P images sampled (E-cinema). This system is not compatible with 2 K DCI. The specifics of the film industry in India is that Indian films (700 films a year) look only Indian viewers. No Indian film was not shown in recent years in international film distribution.
Thus, all of E-cinema is fundamentally inconsistent with the recommendations developed by DCI digital cinema electronic systems.
6 Ecology visual perception of digital images on the screen.
In mid-2003, in the literature there have been reports that the observation of images formed by some models of DLP video projectors (meaning single-chip DLP projectors) leads to fatigue of the visual analyzer, and is sometimes accompanied by dizziness and general malaise.
The single-chip video projectors to produce a color image using the principle of a consistent color. With consistent color reproduction every color image frame is formed by sequential projection of red, green and blue components of the color image. To implement such a projection uses a rotating disc with three color filters — red, green and blue.
Each picture element on the screen, moreover, sequentially changes its color during scanning of one frame. Synthesis of the color image in this case occurs in the human visual analyzer. It is obvious that the system can generate sequential color artifacts in a color fringing smear of moving objects. In addition, the color palette in the technology consistent color is largely determined by the subjective properties of each viewer (similar to the color sensation in the circle Benham) and creates an increased load on the visual analyzer, forcing him to work in unusual for a mode of synthesis of the color image of three successive other color separations.
In some models, single-chip DLP video projectors, in addition to the specified color filters added transparency in the sector, which under certain conditions provides an increase in the luminous flux of the projector is 15% — 20%.
Method serial colors considered in the mid-20th century as one of the principles of the system of color television. Experiments with consistent color reproduction shown that this method has serious fundamental deficiencies, the main of which is the inevitable appearance of color fringing on moving subjects (color break). In addition, the serial transmission of flowers leads to inadequate color sensations at different audiences. For these reasons, the method of serial color was considered unfit for advanced color systems. Hence it can be concluded that the use of the serial transmission colors in a single-chip DLP video projectors will result in inevitable occurrence of said disadvantages.
In 2004, together with the firm NIKFI Activision and magazines edited by TCI and «Presentation» conducted a study of the quality of images generated by various types of digital projectors in a corresponding film screenings in theaters. For the test were used 8 different models of LCD and DLP projectors with a resolution of up to 1 K. The cost of projector models was 52 000-130 000. The results of these tests, which were published in these journals, it is concluded on the deterioration of the image quality of 35mm cinema. Noted the lack of resolution, insufficient contrast, color reproduction is poor, poor uniformity of brightness and color across the image field. In most of these risks and uncertainties relate to the cheap single-chip DLP projectors.
7 From the practical experience of the organization of the first systems of electronic cinema in the Soviet Union in 1978 — 82 years.
In accordance with the decisions of the Government of the Soviet Union in 1978 — 82 years. to create a network of domestic videoprosmotrovyh hall was procured and installed 1000 sets of facilities for group viewing of video, including the Russian Federation, more than 600 plants. To demonstrate the use the content recorded on the magnetic tape (hereinafter to as DVD disks) in a television standard with 625 lines 50 fields / sec. We used video projectors with reflective screens having diagonal
— — 4 meters.
The resolution of the screen image according to the television standard does not exceed 500 horizontal lines, which corresponds to 1000 samples in the digitized video image. From the above it can be concluded that the resolution of the screen display when using TV content, expressed in digital form, it amounts to about 1K.
Videoprosmotrovye rooms for collective viewing of television films have existed for 10-15 years and have substantial economic support to regional film distribution during the adjustment period. However, to date the interest of spectators to such spectacular events completely dried up. The reason for this is the relatively low quality of the screen image to the same audience could see the same movie at home on the TV screen at the same picture quality and sound.
In accordance with the recommendations of the DCI digital cinema systems, electronic quality of the screen image and sound should be at least no worse than in the current system of 35 mm film cinema. In advanced systems ETSK quality of the screen image should exceed the quality of 35mm film cinema.
— Trying to use for electronic digital cinema projectors relatively cheap with a resolution of about 1K shows the incompatibility of such a projection system with 2K and 4K content recommended by DCI. Also, use of low cost single chip DLP projector with a resolution of 1K leads to a number of artifacts in the image (bundle colors with head movement in distortion of the «step» at the inclined lines visibility of the pixel structure and m. P.) And fatigue of viewers when viewed such images.
— Having domestic operating experience of e-cinema with a resolution of the order of 1 K leads to the conclusion about the unwillingness of spectators attending kinozrelische such as a similar image quality a viewer can watch on your home TV screen.