5 SVG-based Timed Graphics

26.4303GPPRelease 17Timed graphicsTS

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

5.1 Introduction

SVG-based Timed Graphics is defined as a profile of DIMS with certain restrictions and a layout mechanism for rendering timed graphics with external continuous media (i.e. video). Similarly to DIMS, SVG-based Timed Graphics consists of a multimedia scene. The multimedia scene is described using SVG Tiny 1.2 [2] and may consist of any combination of still pictures and animated graphics. In SVG-based Timed Graphics, continuous media such as audio and video are not allowed and shall be ignored by the receiver. The profile limitations are described in the following sections.

5.2 Scene Description Restrictions

SVG Tiny 1.2 shall be used for the description of SVG-based Timed Graphics. The base scene description shall not contain any references to continuous media such as audio or video.

The following restrictions to SVG Tiny 1.2 apply to the SVG scene of SVG-based Timed Graphics:

– Timed Media Elements: audio, video, and animation elements shall not be present in a timed graphics scene and should be ignored by the timed graphics client.

– Interactivity: scripting and handling of events is not allowed and shall be ignored by the timed graphics client.

Furthermore, SVG-based Timed Graphics scenes should not contain any elements or attributes from DIMS scene extensions.

5.3 Scene Commands

Timed Graphics does not support scene commands. In a Timed Graphics scene, DIMS scene commands should not be present and shall be ignored by a terminal that conforms to this specification.

5.4 Timed Graphics Media Unit Restrictions

SVG-based Timed Graphics media units are DIMS media units that are restricted to complete SVG documents. The DIMS compression method may be applied to Timed Graphics unit body.

For Timed Graphics the Unit header fields shall be set as follows:

S: is-Scene: shall be set to 1 and may be ignored by a Timed Graphics decoder.

M: is-RAP: shall be set to 1 and may be ignored by a Timed Graphics decoder.

I: is-redundant: shall be set to 0 and may be ignored by a Timed Graphics decoder.

D: redundant-exit: shall be to 0 and may be ignored by a Timed Graphics decoder.

P: priority shall be set to 1 and may be ignored by a Timed Graphics decoder.

C: compression: indicates the compression applied;
0 indicates no compression (textual format);
1 indicates that the content is compressed using the encoding signalled in stream setup.

X: reserved: shall be set to 0 and shall be ignored by the receiver

5.5 Timing model

Timed Graphics consists of a sequence of SVG scenes where each incurs a reset of the scene time to 0. The synchronization to external continuous media is achieved using the transport protocol (RTP) timestamps and the sample timestamps in the 3GP file format.

The SVG scene itself defines its own timeline, which has as origin the time that corresponds to the presentation time given by the RTP or sample timestamp. The usage of internal timelines should be limited to timing the presentation and removal of the graphics content. This is ensured by disallowing continuous media components including the animation element in the SVG scene for timed graphics.

5.6 Processing Model

In SVG-based Timed Graphics, a Scene Description is a random access point (RAP) and is processed as a complete replacement for the current scene tree. That is, the entire DOM is discarded and replaced with the result of parsing the newly received SVG element.

The following state diagram illustrates the states. The state diagram should be implemented by timed graphics terminals.

In the state diagram, the terminal may be processing a stream under one of two conditions:

a) normal processing, ‘normal’;

b) after tuning in, performing random access, or when loss is detected, ‘tune-in’.

Tune-in state is entered under any of the following circumstances:

a) after opening a stream;

b) after performing random access;

c) after loss of a timed graphics Unit in normal processing.

The terminal transfers to ‘normal’ state after processing any received timed graphics sample.

Figure 2

5.7 Rendering Model

The <svg> root element of the Timed Graphics scene shall be rendered on the parent canvas (provided by the media player) originating at the upper left corner. The <svg> element shall be completely transparent and should contain the attribute "viewport-fill" that shall be set to "none".

Timed Graphics media shall have a higher rendering order than other continuous media such as video and timed text. In case multiple Timed Graphics streams co-exist in the same multimedia session, the rendering order shall be established based on the media identifiers, or, if not present, the order of appearance in the 3GP file or the SDP.

5.8 Transport

SVG-based Timed Graphics uses from the same transport mechanisms as DIMS. It may be downloaded using HTTP, as part of a file format or it may be streamed over RTP.

Timed Graphics reuses the DIMS RTP payload format and the 3GP file format extensions. The Timed Graphics also reuses the SDP syntax and media type parameters defined for DIMS. The profile shall indicate Timed Graphics by carrying the value 5.

5.9 Timed Graphics Profile

A new Profile Indicator with value 5 is allocated for the Timed Graphics profile.

Support for the following media types shall also be supported in Timed Graphics Profile:

– The Still Image media formats and the Bitmap Graphics formats of [3].

As required in the SVG specification, SVG fonts shall be supported. The lack of hinting in SVG fonts means that small text which is anti-aliased may become unreadable. This problem is even more evident when text is rotated or animated. Recommendation: SVG fonts should be used with care.

The Open Font Format [4] should be supported at advanced simple text profile, level 2, with the following constraints: if Open Type fonts are supported, the DIMS Timed Graphics Profile client shall support downloadable OpenType fonts with TrueType outlines, TrueType hinting shall be supported for improved text readability, and advanced typographic features may be supported.

Note: When OpenType fonts are supported, download of them may be initiated using the font-face-uri element from [1].

Device-native fonts and fonts identified by generic family names may be used.

5.10 Timed Graphics Level 5

This level contains the following restrictions:

Table 1: Timed Graphics Level 5 Limits

	Level 5
Scene bitrate (includes the static media embedded within the scene/commands and referenced media payloads)	200 kbit/sec
Simultaneous video playing	0
Simultaneous audio playing	0
Simultaneous active Timed Graphics scenes	1
Minimum pixel output buffer size	16 wide by 16 tall
Maximum path segments across all paths	3000
Maximum text content size (this refers to the number of characters and does not include the glyph)	10k bytes
Maximum dash array size	16
Maximum number of gradient stops	32
Maximum recommended DOM tree size	20 nodes
Minimum recommended screen refresh rate Note: Depending on the DOM tree size, the recommended screen refresh rate value may not be feasible and a lower screen refresh rate might be expected.	0.2 frames/sec