The term ASCII (American Standard Code for Information Interchange, pronounced "ask-ee") properly refers to a seven-bit binary encoding of many English-language letters, punctuation, and mathematical symbols. This was initially adopted as ANSI X3.4-1968, with later revisons.

In theater lighting, ASCII is usually a colloquial term for "USITT/ASCII", which refers to a published standard of the United States Institute for Theater Technology. The last edition of this document was marked "ASCII Text Representation for Lighting Console Data, Version 3.0, Ident 3:0, March, 1992." While the paper document is no longer sold by USITT, a 3 megabyte scanned .PDF version of the standard is available for free download.

Note that the term ASCII is sometimes used in its formal computer science meaning within the theater business. The most common example would be in the choice of a printer output format. This usually relates to the handling of line spacing and boldfaced text, rather than to this Wiki topic.

The Standard

The document provides a formal grammar for describing many aspects of a lighting console's show data, to permit study and editing without a console, and to permit show exchange between otherwise incompatible consoles. For example, one cue might look like this in a USITT/ASCII file. Not every line in this example is covered by the standard. Especially on the internet, the tenth line of the example may wrap confusingly on your screen. But it's included because the standard limits the maximum length of a file line to 80 characters. The "asterisk" line is provided to encourage the user to set the text editing program to view lines of that length correctly. The lines have been padded with spaces so that the "@" signs line up vertically.

Sample File

! USITT ASCII Text Representation for Lighting Console Data format.
! Translated from board listing file by LST TO ASC - Version 1.0
! Date: 9/12/2002 15:35
! User name: Development Copy
! Product Serial Number: 101
! Input filename was: PIANOQ.TXT
! Command Line Args: None
! Adjust word processor margins or font or size
! so that all *s fit on next line.
!*******************************************************************************
IDENT 3:0
MANUFACTURER Tracking Associates [made-up company name]
CONSOLE BoardWalk(Light)

! CUE TIME WAIT FOLL LINK PROF RATE BL PK LABEL
! 0.5 10
CUE 0.5
UP 10
DOWN 10
! TRACKING CHANNELS
! (none)
! MOVING CHANNELS
CHAN   29@100   30@100
CHAN  230@80   231@70   232@100  233@100  235@33   236@90   237@100  238@100

ENDDATA

It's worth noting that comment lines like "! TRACKING CHANNELS" have no effect on the next use of the file. The standard states that any channel with a non-zero level must appear in a cue's listing. If the user edits the file, the heading (i.e. TRACKING) may no longer be precisely accurate. But the channel will still go to whatever level the user provides in the file.

The standard prescribes this list of delimiter characters, all of which are treated identically. A contiguous string of delimited characters is to be treated as if there were one delimiter:

  (tab)
  (space)
, comma
/ slash
; semi-colon
< less than
= equal
> greater than
@ at sign

Some systems may use the characters >, =, and < instead of @, to indicate whether the level that follows is increasing, decreasing, or tracking. The same editing caveat above applies to edits of the level numbers.

Real-World Implementation

There are many aspects of console shows that are not covered by the USITT document. In addition to later developments (like moving lights), the original standard does not cover effects or macros, which existed at the time of publication.

In parallel with the development of the formal standard, various manufacturers used similar means to represent either optional output from their Lighting Desks or Off Line Editor, or in some cases, the actual native show file format. When necessary, they developed extensions to the standard. For example, Strand ASCII output (from the Showport program) uses the keyword "Attrib" for non-intensity attributes. Note that the standard requires that channel number data be integers, so the decimal fraction notation of Strand attributes requires another extension to the standard.

Shortcomings

Although the standard attempts to be exhaustive, ambiguities can arise. An example is whether Part cues should have multiple PART keywords under a single CUE keyword, or whether there should be a CUE and PART sequence for every Part. Because of development time and labor cost factors, the intended opportunity to use the Version,Ident,and Manufacturer keywords to uniquely and exhaustively specify how to parse every possible ASCII file has often been missed. In any case, there is no way to anticipate new features in software released after any particular USITT/ASCII-processing system's creation.

Another source of ambiguity is that DMX512-1990 data offer 256 levels of dimmer output, so that, depending on the conversion algorithm used by the destination desk, a decimal level number (0-100, or 101 levels) in a USITT/ASCII file may map to two or more different DMX levels. This was not important in setting the brightness of an incandescent lamp, but it can make a difference in control of an accessory or moving light.

Free-standing software has also taken advantage of the USITT/ASCII standard. Lighting paperwork programs (like Lightwright) typically output an ASCII patch file, using the channels and dimmers that the user has typed into the paperwork program. The program Trackmaster was developed to mimic a generic lighting console to permit editing USITT/ASCII shows, but free Off Line Editors have eliminated the market for such products.

See also

• DMX DMX512-1990 Standard (ANSI E1.11 - 2004)
• Remote Device Management

References

ASCII Text Representation for Lighting Console Data Version 3.0 .PDF file

External Links

• ESTA (.PDF) Minutes of Control Protocols Working Group March 21, 1997
• Lightwright
• Virtual Magic Sheet