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Content for  TS 26.430  Word version:  17.0.0

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0  Introductionp. 5

Timed graphics is a media type that enables advanced subtitle like services in parallel to video. It enables high quality text and graphics at a low cost.
In low bit-rate video, the areas which are often perceived as the worst are subtitles and graphics or tables (encoded as part of the video). Encoding subtitles as timed text instead of as part of the video can increase the perceived quality of the video substantially. Timed Text [4] solves the problem of subtitles and when used gives a perceptual quality much higher that encoding the text as part of the video stream. DIMS [5] allows the placement of vector graphics on top of video - but from an application perspective and requires DIMS to control the media. Timed Graphics works together with these abovementioned specifications, or independently, to enable better "video" quality.

1  Scopep. 6

The present document defines a timed graphics media type which reuses components from existing media types. A transport system is defined as is a storage format.
The specification is written in a forward-compatible way in order to allow additions of media components and functionality in future releases.
It enhances the user experience by enabling graphics to be encoded as graphics (as opposed to video) and without requiring an umbrella system such as SMIL or DIMS.

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