MHEG-5
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MHEG-5 is a standard devised for the middleware of digital teletext services in the United Kingdom. Officially ISO/IEC 13522-5 it was evolved from the standards devised by the Multimedia and Hypermedia information coding Expert Group (MHEG) and specifies the classes of multimedia objects available and their interchange. The ISO standard is now enhanced by a European standard to be published by ETSI ES 202 184, which is an MHEG-5 Broadcast Profile based on the work in the UK.
Being based on the multimedia standard, MHEG allows for much more than simple page display of teletext, for example MHEG-3 covers scripting and MHEG-6 interactive applications. It is an object orientated language with visible objects, groups, inheritance, links and programs. A MHEG-5 presentation is initialised by an application which loads a scene which includes the ingredients list of visibles and also the non-visible links, programs and variables.
// 'Hello world' written in MHEG-5
// Originally from http://www.digvid.info
{:Application
( '/startup' 0 ) // Application content reference
:Items (
{:Link
1
:EventSource 0 // Check this application...
:EventType IsRunning // ... for the IsRunning event
:LinkEffect (
// Load the scene
:TransitionTo (( '~/hello.mhg' 0 ) )
)
}
)
:BackgroundColour '=FF=FF=FF=00' // White
:TextCHook 10 // Default text content hook
:TextColour '=00=00=00=00' // Black
:Font "rec://font/uk1" // Font to use for text rendering
:FontAttributes "plain.26.32.0" // Default font attributes
:BitmapCHook 4 // Default bitmap content hook
}
{:Scene
( "~/hello.mhg" 0 )
:Items
(
// Declare a background Rectangle that covers the screen.
{:Rectangle
1
:OrigBoxSize 720 576 // Size of rectangle
:OrigPosition 0 0 // Position at top left
:OrigRefLineColour '=ff=ff=ff=00' // White
:OrigRefFillColour '=ff=ff=ff=00' // White
}
// Place a Text box on the screen
{:Text
2
:OrigContent "Hello World!" // Text to display
:OrigBoxSize 300 50 // Size of text box
:OrigPosition 200 100 // X,Y position
:FontAttributes "plain.36.42.0" // Use large characters
:TextColour '=ff=00=00=00' // Red
}
// Define a Link that triggers when the user presses the Blue key to
// Quit the application.
{:Link
3
:EventSource 0 // Source is this scene
:EventType UserInput // Event type that we are looking for
:EventData 103 // 103 for the blue key
:LinkEffect (
:Quit ( ( '~/startup' 0 ) )
)
}
)
:InputEventReg 3
:SceneCS 720 576
}
External links
- MHEG Official site (http://www.mheg.org)
- Hello World in MHEG-5 (http://www.digvid.info/mheg5/hello_world.php)
- MHEG (pdf) (http://www.dtg.org.uk/reference/mheg/_mheg_index.html)
- MHEG jobs (http://www.dtvjobs.co.uk/wikipedia/mheg)
- End-to-end MHEG systems and applications (http://www.mheg.tv)
- Open Source ASN.1 MHEG-5 codec (http://lionet.info/asn1c)