digital_technology

DVB

The DVB Project is an Alliance of about 200 companies, originally of European origin but now worldwide. Its objective is to agree specifications for digital media delivery systems, including broadcasting. It is an open, private sector initiative with an annual membership fee, governed by a Memorandum of Understanding (MoU).

Until late 1990, digital television broadcasting to the home was thought to be impractical and costly to implement. During 1991, broadcasters and consumer equipment manufacturers discussed how to form a concerted pan-European platform to develop digital terrestrial TV. Towards the end of that year, broadcasters, consumer electronics manufacturers and regulatory bodies came together to discuss the formation of a group that would oversee the development of digital television in Europe.

This so-called European Launching Group (ELG) expanded to include the major European media interest groups, both public and private, the consumer electronics manufacturers, common carriers and regulators. It drafted the MoU establishing the rules by which this new and challenging game of collective action would be played.

The concept of the MoU was a departure into unexplored territory and meant that commercial competitors needed to appreciate their common requirements and agendas. Trust and mutual respect had to be established. The MoU was signed by all ELG participants in September 1993, and the Launching Group renamed itself as the Digital Video Broadcasting Project (DVB). Development work in digital television, already underway in Europe, moved into top gear.

Around this time a separate group, the Working Group on Digital Television, prepared a study of the prospects and possibilities for digital terrestrial television in Europe. The highly respected report introduced important new concepts, such as proposals to allow several different consumer markets to be served at the same time (e.g. portable television and HDTV).


Digital formats in pre-press

TIFF/IT is a standard for the exchange of digital adverts and complete pages. TIFF/IT files only contain bitmap data, no vector data. The files are not rasterized (although they could be) but they contain 256 graylevels per channel. TIFF/IT is the abbreviation of Tagged Image File Format/Image Technology. As the name indicates, TIFF/IT is based on the well known TIFF standard. Because the TIFF/IT standard is very flexible, a subset of the standard was devised that is called TIFF/IT P1. P1 is limited to CMYK jobs. It does not support spot colours. When most people talk about TIFF/IT, they refer to the P1 version. A P2 version was in the works for a long time and may never make it, given the decreasing popularity of TIFF/IT.
TIFF/IT has only been successful in some markets like the exchange of adds for newspapers or magazines and the exchange of pages for magazine printers. In the past years, its role has largely been taken over by the PDF file format, more specifically PDF/X-1a.
From around 2000 to 2004 a number of companies selling TIFF/IT related products announced products in which TIFF/IT data were encapsulated in PDF files. This merging of these two formats, with PDF offering wide industry support and TIFF/IT’s proven track record of reliability, was an interesting concept but I don’t think any of these hybrid formats are still in widespread use. RIPs would frequently choke on such files and vendors were reluctant to actively support odd file formats.

The history of TIFF/IT

The history of TIFF/IT starts around 1989 when DDAP (the Digital Distribution of Advertising for Publications Committee) asked ANSI, which is the American National Standards Institute, to define a standard for the exchange of digital adverts.
ANSI has its own subcommittee that deals with graphics arts and this committee, called CGATS, decided to start with the development of a standard for the exchange of raster data. They planned to add another file format for vector based data later on.
CGATS took the TIFF file format as a starting point. The most current version of the TIFF specs is still version 6.0, defined by Aldus way back in 1992.
In 1996, the specifications of TIFF/IT were finalised. TIFF/IT was a very open and powerful format that left a lot of room for developers to handle things in different ways.

Different versions of TIFF/IT

The versatility of the original TIFF/IT specs soon proved to lead to compatibility issues between the software of different vendors.

TIFF/IT P1

To avoid these compatibility issues, a more limited version of the standard was developed, which is called TIFF/IT P1 (also known as ISO 12639). The P1 stands for Profile 1. When most people talk about TIFF/IT, they mean the P1 standard.
TIFF/IT P1 files normally consist of 3 files. The standard is tuned for CMYK files and cannot really handle spotcolours. TIFF/IT P1 got an ISO certification and is now officially the ISO 12639 standard.
Several companies lanced new applications or adapted existing software to support TIFF/IT P1. Scitex is among the most prominent supporters of P1 which is not too surprising if you see the similarities between P1 and their own CT/LW file format. Other companies like Shira build conversion tools to integrate TIFF/IT in existing PostScript or PDF workflows.
Nowadays TIFF/IT P1 is an established standard for the exchange of adverts and full pages for markets like newspaper production or gravure printing. In some countries like France it dominates the market.

TIFF/IT P2

Because TIFF/IT P1 had a number of limitations, a group of companies joined forces to develop an extended format, to be called TIFF/IT P2.
P2 was supposed to add a number of functions like:
•Support for the compression of CT data (either JPEG or Flate) which would allow for smaller files
•Support for multiple LWs and CTs in a single file
•Support for copydot files through a new file type called SD (Scanned Data)
•The possibility to concatenate FP, LW, and CT files into a single file called the GF (Group Final) file.

The TIFF/IT P2 specs took a long time to get finalized. Meanwhile the PDF file format was picked up by the industry and TIFF/IT quickly became an obsolete file format. P2 simply was too late and PDF/X-1 became the successor to TIFF/IT P1.

The TIFF/IT file format

Contrary to what the name suggests, a TIFF/IT file is actually composed of a set of files. TIFF/IT P1 files usually consist of 3 files:

•a Final Page or FP file
•a Continuous Tone image (known as a CT)
•a Line Work image (known as the LW)
Besides these 3 files, TIFF/IT files can contain some other files as well, such as:

•a High resolution Contone file (also called HC)
•a Binary Linework or BL file
•a Binary Picture file (BP in short)
•an MP or Monochrome Picture file

The naming conventions of TIFF/IT files are quite strict. To avoid problems, you should stick to the lowest common denominator of all platforms used to process the files. This means that filenames should contain less that 25 characters, only contain numbers and letters and end with the appropriate extender (.LW for the Line Work file, .CT, .FP and so on).

Below is a short description of some of the filetypes.

The FP file

The final page file is a kind of reference file. It points to the corresponding CT and LW file and contains offsets that describe where the CT and LW should be placed on the page. The CT is placed on the page first, then the LW is laid over it. The LW usually has some transparent areas where the CT will show through. Because it is only a reference file, the FP file is rather small.

The CT file

The CT or Contone file contains, as you would expect, all photographic imagery. Although it can be any resolution, it usually has a resolution of about 300 dpi. It can contain any CMYK colors in 8-bit, meaning there are a maximum of 256 shades of cyan, magenta, yellow and black.

The TIFF/IT P1 specs do not allow for datacompression within the CT file. This means that its size is rather large, about 40 MB for an A4 size file. It also means the size is fixed, regardless of the content of the page.

The LW file

The Line Work file contains high resolution data like line art images, text or lines from drawings. Unlike line-art files, the LW file is indexed, meaning that every pixel in the file can be colourized. There is a fixed list, or index, of all colours that are used within the LW file. This index contains a maximum of 256 colours. The LW file can also contain transparant area’s where the underlying CT file shines through.

The LW is usually at a high resolution, such as 2400 dpi. As a general rule, the resolution of the LW file should be an exact multiple of the resolution of the CT file. Ideally the resolution also matches the resolution of the imagesetter used to output the file.

The LW file can be compressed so that its filesize usually does not exceed 10 MB or so for an A4 size document.

The MP file

A CT file can only contain CMYK colours. To support spot colours, a TIFF/IT file can contain MP files. An MP file is a single colour contone file, used to describe the image data of the spot colour. Think of it as a kind of monochrome CT file.

MP files are not compressed and occupy about 10 MB for an A4-size document.

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