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Timecode User Guide


1. Acorn TimeCode User Guide


Multimedia hardware devices and software applications which can store, manipulate and present time based data such as animations, video, audio, MIDI and presentation timelines can be synchronised by the Acorn TimeCode subsystem using industry standard MTC timecodes. This provides the application developer and end user with a seamless, easy to use interface which eases the development of broadband multimedia presentations.

By using this software a RISC OS application or a hardware device attached to a Risc PC can receive, generate or propagate a high resolution time stream. The direction and rate at which time flows across the timestream can be controlled by the application or hardware device, and the timestream may be routed from the application to other hardware or software clients.

The RISC OS computer system now becomes capable of synchronising with or controlling a range of other devices which also have an awareness of time. Examples of these devices include MIDI sequencers, synthesisers, samplers and multitrack tape decks, and CD-ROM drives and other computer systems.

Suitable interface hardware (such as a MIDI card) is used to allow reception and transmission of the time stream from and to external sources.

The TimeCode subsystem provides support for full and quarter frame MTC, and the 75fps frame addressing of Red Book audio CD. In addition to these default rates, frame rates from 1fps to 1800fps are supported.

Timecode can be routed between applications with on-the-fly conversion of differing frame rates. It is possible for instance, to use the 75 fps timing on an audio CD to produce MTC streams at 30 fps. Here, the CD could act as the timing source for the MIDI system. Other time-aware devices such as sequencers can follow the time stream from the CD and are therefore synchronised with it.

TimeCode is currently being developed by Acorn Risc Technologies.

The software provided here is all pre-beta. We believe it is stable enough to be used, but should be considered to be provided 'as is'.

Download a copy of the sources to CD-Deck and Timespeed



!Karaoke was written using Desktop C; and requires RISC_OSLib. The other applications were written using Acorn C/C++ and require the various toolbox modules rmensured in each !Run file plus TinyStubs.

Software structure


A directory containing various TimeCode-aware applications:


This application can control a CD-ROM drive. If used with a conventional audio CD it can read the timecode stream present on every audio (Red Book) CD and use it to update the TimeCode system's Internal Clock.

Click Select on the icon bar icon to open the CD Player window.

This window contains five buttons, which have these functions (reading from left to right):

The display field to the right of the buttons shows the current time from the CD, in mm:ss:ff format. Hours are also displayed when necessary.

The display field below the icons gives a status indication for the application and the CD-ROM transport.


This application can be used to display time-synchronised information. Unlike the other applications here it only works to second resolution; it was originally conceived for displaying the words to a song (using the timecode stored on an audio CD). However, it has many more applications than that - anything which involves time-synchronised information. In the example here we've used it to display some explanation about the uses of timecode. You'll see that it begins at 00:58:00:00 - this is a default starting time within the audio/video industry; though it's usually the start of two minutes of lead-in rather than directly into programme information as here.

The name of the file to use is given in the !Run file. The layout of the file indicates its original design - the first line of the file must contain a time and a [Album] tag. The content of this line is placed on the top line of the window. This is then followed by one or more [Track] lines which give the name for a given track; that is - what to display on line two of the display.

One other special line is supported - [Quit] which can be used to make !Karaoke exit.

All other lines will consist of a time stamp in hh mm ss followed by the text (if any) to display.

The display consists of a number of lines in light blue, with the current line in dark blue.

!Karaoke will follow timecode wherever it goes; automatically adjusting direction or taking account of jumps in time. Put simply it makes no assumptions about the direction or speed of time flow. This is an essential point to note about timecode; it cannot be guaranteed to be advancing forwards monotonically; indeed it could be going backwards or not moving at all - and if moving may well not be doing so at real time.


This is basic example of an event scheduler built to operate on timecode. It provides minimal editing facilities, and its display is not very graphical - it was written to demonstrate the potential of the concept rather than be the last word in showing it.

The textual files inside the directory describe the file format for the event file. When it starts up it reads in the file !Scheduler.Default, and it saves the modified data as !Scheduler.Output when the application exits.

You are advised to open the display window by clicking Select on the icon bar icon - this improves the response.

The default file included with this version is the schedule file used to animate the Acorn Conductor at Acorn World - timecode was drawn from an audio CD and the scheduler issued pollword changes to the application responsible for animating the Acorn Conductor.


This application is provided to allow control of the timecode system from the desktop environment. It allows clock and clock transmitter selection; provides control over the Internal Clock and provides diagnostic facilities such as a switchable display of the current timecode at a fps rate chosen by the user.

Note that changes will not take effect until OK is clicked upon, and certain controls will have a transitional state where you cannot make further changes because a change is already pending (for example starting the Internal Clock).


This application provides a finer control over the Internal Clock. You may have as many copies of this application, !TimeShare or !Karaoke as you wish loaded and they will all stay in step with each other.

You will notice this particularly with !TimeSpeed. The display field gives the rate that the Internal Clock is running at in comparison to real time. If you have more than one invocation of !TimeSpeed running you will see they all remain locked to one another.

Most of the buttons are multi-purpose - reading from left to right they operate as follows:

The display field next to the buttons is used to display the current time flow, and the display field at the right of the window shows the current timecode value expressed in 25fps.

Useful Documents


Fill out this template and send it as email to skynet-comment@art.acorn.co.uk. Try to give as much information in as impartial fashion as possible. If we can't reproduce a problem due to insufficient information we stand little chance of fixing it!


contains an indication about what we're thinking of for the future


This is an internal *draft* document giving a proposed wimp message interface to allow applications which handle resources which are timecode-aware to interface with a application/resource manager which would handle all the interlinking between all such applications and resources. Amongst other things it could remove the need for most every application to have a tape-transport style of its own which is subtly different to every other one.


These are supplementary and replacement items for !Boot

See the ReadMe file for additional information. RISC OS 3.10 users should manually update their !System to have the same structure as is represented within the !Boot.!Resources.!System here.

Note that this is NOT a replacement !Boot for RISC OS 3.50 or RISC OS 3.60 users - it contains additional and updated items which must be merged correctly with your existing !Boot structure.


This is a timecode interface library for C

This directory contains the TimeLib library and its associated header file.

This library provides a simple interface to all the SWIs which are provided by the TimeShare module. By supplying a library only those functions you need will be incorporated in the object code. Note that wimplib is also needed.


This material is provided for personal use only. If you wish to include the TimeShare module, or anything else here, in distributed code you should contact ART for licensing terms. Although the software here is in an advanced state, we reserve the right to make any changes to the software or its interfaces we deem necessary or desirable. If you are considering building a product using this technology you are advised to contact ART for advice beforehand.

This edition Copyright © 3QD Developments Ltd 2015
Last Edit: Tue,03 Nov 2015